FOUS30 KWBC 060816
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
416 AM EDT Sun Jul 6 2025

Day 1
Valid 12Z Sun Jul 06 2025 - 12Z Mon Jul 07 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
CENTRAL TEXAS AS WELL AS FOR PORTIONS OF THE CAROLINAS...

...Carolinas/Southern Virginia...
Tropical Storm Chantal is forecast to move inland across
northeastern South Carolina early in the period and weaken as it
moves into central North Carolina later today into the overnight.
The growing consensus of the model QPF has an "occluded look" to
it, with the heaviest amounts setting up west of the track. Not
much change was made to the previous Slight Risk area, with minor
adjustments based on the new HREF guidance. This area reflects the
HREF higher neighborhood probabilities for 3+ inches, which extend
from parts of the Pee Dee region and north-central SC through
central NC into far south-central VA.

...Central Texas...
Fueled by a lingering axis of deep moisture (2 to 2.25 PWs
according to recent runs of the RAP) and weak mid level energy
drawn south by an upstream ridge, concerns remain for additional
heavy rains and flooding across portions of North Texas back into
South-Central Texas and the Hill Country. QPF has trended upward
within the highlighted region, with the HREF once again showing a
strong signal for locally heavy amounts over 3 inches within the
Slight Risk area. These amounts would easily exceed FFGs over those
areas recently impacted by heavy amounts. Therefore, will continue
to monitor for the potential need to upgrade to a Moderate Risk
for parts of the region.

...Upper Great Lakes to the Central Plains/Ozarks...
A series of shortwaves will move through a broad upper trough
centered over the northern Plains, pushing a wavy cold front, that
extends from the upper Great Lakes back into the central Plains,
farther south. A deep moisture pool ahead of the front (PWs over 2
inches in some locations) will fuel widespread shower and storm
coverage. Overnight guidance indicates that in addition to the
ample moisture, favorable upper jet dynamics and some potential for
storm training, will contribute to a greater threat for heavier
amounts (2-3 inches) across parts of Lower Michigan. However,
locally heavy amounts, along with isolated flooding concerns,
cannot be ruled out further southeast along and ahead of the front.

...Central and Southern High Plains into the Southern Rockies...
Moist upslope flow will contribute to afternoon storm initiation
along the high terrain, with the guidance continuing to present a
notable signal for organized development contributing to heavy
amounts across portions of western Kansas and Nebraska. The
overnight HREF indicates 2-3 inches are likely for parts of the
region. Storms are expected to remain less organized further to
south, but may fire and produce isolated flooding concerns across
the more vulnerable parts of central and eastern New Mexico.

...Southern Louisiana/Mississippi...
Models show an upper low over the northeastern Gulf retrograding
westward back along the Gulf Coast. This will bring increasing rain
chances to the region, with the potential for heavy amounts. A
Marginal Risk was maintained for parts of southern Louisiana and
southwestern Mississippi, where the HREF presents a strong signal
for amounts over 2 inches.

Pereira


Day 2
Valid 12Z Mon Jul 07 2025 - 12Z Tue Jul 08 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE UPPER
MIDWEST TO THE SOUTHWEST, THE NORTHEAST TO THE SOUTHERN PLAINS,
PORTIONS OF CENTRAL TEXAS, AND EASTERN NORTH CAROLINA TO EASTERN
PENNSYLVANIA AND NEW JERSEY...

...Eastern North Carolina to Eastern Pennsylvania and New Jersey...
Although the surface circulation may no longer be well-defined,
the mid level remnants and an its associated plume of deeper
moisture are expected to lift north from eastern North Carolina
along the Mid-Atlantic Coast ahead of an upstream trough, bringing
the potential for locally heavy rain and perhaps some isolated
flooding concerns from eastern North Carolina to eastern
Pennsylvania and New Jersey.

...Northeast to Mid Mississippi Valley/Ozarks...
A frontal boundary will continue to slide farther east across the
Northeast this period. Deep moisture ahead of the boundary (PWs
1.75-2 inches and 2-3 std dev above normal), along with favorable
upper jet forcing are expected to contribute to some organized
heavier amounts from western and northern New York into parts of
northern New England. Less organized activity is expected farther
southeast. However, once again locally heavy amounts and isolated
flooding concerns cannot be ruled out for areas back through the
Ohio Valley into the mid Mississippi Valley and Ozark region.

...Southern Plains...
The latest HREF shows that activity developing over parts of Texas
on Day 1 may continue into Day 2, producing additional heavy
amounts and prolonging flooding concerns across parts of Texas
including portions of South-Central Texas and the Hill Country
northeastward through North Texas...

...Upper Midwest to the Southwest...
Amplifying southerly low level winds over the Plains will support
increasing moisture across the central into the northern Plains.
This moisture along with mid level energy moving out into the
region, will support widespread showers and thunderstorms, with
the guidance showing a signal for organized activity developing
over the central High Plains. Forecast confidence is limited by
significant model spread in the details. However, the potential for
at least isolated flash flooding concerns cannot be ruled out.

Farther to the south, activity again is expected to be less
organized. But again, cannot rule out at least an isolated flash
flooding concern, especially across vulnerable portions of eastern
and central New Mexico.

Pereira


Day 3
Valid 12Z Tue Jul 08 2025 - 12Z Wed Jul 09 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE MIDWEST
AND THE NORTHEAST TO THE SOUTHERN HIGH PLAINS...

...Northeast through the Ohio Valley...
A cold front will continue to slide slowly southeast across the
Northeast and the Mid Atlantic. Deepening moisture ahead of the
boundary (increasing above 2 inches in many locations) will raise
the potential for at least locally heavy amounts and isolated
flooding to occur.

...Midwest to the Southern High Plains/Rockies...
An upper level shortwave and associated axis of deeper moisture may
produce storms with locally heavy amounts from the mid Mississippi
Valley/Great Lakes region back through the mid Mississippi and
lower Missouri valleys into the southern Plains.

Meanwhile, low level upslope flow may produce another round of
showers and storms developing along the southern Rockies into the
High Plains.

Pereira

$$
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FOUS30 KWBC 071331
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
931 AM EDT Mon Jul 7 2025

Day 1
Valid 1331Z Mon Jul 07 2025 - 12Z Tue Jul 08 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE HILL COUNTRY OF TEXAS...

13Z Special Update:
After coordination with WFOs San Antonio and San Angelo (Texas),
this special update was created to add a targeted MDT risk for
portions of the Texas Hill Country. Although morning CAMs (pre-12Z
runs) are struggling to resolve the current activity, there is
enough signal, despite timing and placement differences, in the
guidance that concern is elevated for a MDT risk.

A 700mb trough aligned SW to NE will string out across central
Texas through today and remain nearly in place through the evening.
Into this trough, impressive convergence will focus as return flow
emerges out of the Gulf while NW flow concurrently progresses from
the Southern Rockies. Not only will this force ascent, but
examination of CIRA ALPW percentiles reveals that elevated PW
in the low levels (sfc-850mb above the 95th percentile) shifting NW
while PWs in the 700-500mb layer also above the 95th percentile
drop SE. This will force intense moisture confluence into this
trough axis, and the result in very weak 0-6km mean winds of just 5
kts with anti-parallel Corfidi vectors of 10-15 kts. This suggests
that as convection blossoms during the next few hours storms
should move slowly and generally drift W/SW across the Hill
Country. This results in both HREF and REFS probabilities that
reach 60% and 30%, respectively (06Z runs) for 5" of rainfall
through the evening, despite uncertainty in the individual CAMs.

Rainfall already this morning has been expanding with radar-
estimated rainfall rates above 3"/hr, and as instability climbs
this aftn, expect these rain rates to continue as PWs remain above
2 inches. These slow moving storms with these intense rain rates
will additionally move atop extremely vulnerable soils due to 72-hr
rainfall that has been 5-15", causing catastrophic flash flooding
over the weekend and resulting in saturated 0-10cm RSM from NASA
SPoRT and FFG below 2"/3hrs. Any storms that move across this
extremely vulnerable region will rapidly cause flash flooding, some
of which could be significant if cells repeat or stall over the
already hard-hit regions.

Weiss

Previous 09Z Discussion below:

...South-Central Texas...
With the latest CAMs showing a notable signal for an additional
round of slow-moving, heavy rain-producing storms, a Slight Risk
was introduced across South-Central Texas, including the Hill
Country. Recent runs of the RAP show a slow-moving mid level center
drifting southwest toward the Rio Grande, with many of the CAMs
showing convection redeveloping later this morning and continuing
beyond 12Z. The environment remains very moist, with PWs of 1.5-2
inches within the highlighted area. HREF neighborhood probabilities
for accumulations over 2 inches are well above 50 percent within
much of the Slight Risk, with some embedded high probabilities for accumulations over 3 inches as well. The bulk of these amounts are
expected to occur within the first 6-12 hrs of the period, before
waning later today. This includes some of the areas which were
recently inundated by very rains and where FFGs remain quite low.

...Mid-Atlantic...
Influenced by an upstream trough centered over the Ohio Valley, Tropical Depression Chantal is expected to accelerate to the northeast
today, moving out of Virginia and across the Delmarva to the
northern Mid-Atlantic Coast later today. While the increase in
forward speed will provide some limit to the heavy accumulation and
flooding threats, the system will remain an efficient rainfall
producer, with heavy rates likely to raise some flooding concerns,
especially across urbanized and poor drainage areas. Reflecting the
HREF higher neighborhood probabilities for 3 inches or more, a
Slight Risk extending from southeastern Virginia to eastern
Pennsylvania and central New Jersey was introduced. Indicating the
potential for this storm to produce heavy amounts quickly, the
majority, if not all of these amounts are expected to occur within
the first 6-12 hours of the period, before the system moves back
offshore later today.

...Northeast back to the Ozarks...
The previously noted upper trough will edge slowly east across the
Ohio Valley and Great Lakes, with mid level energy and deep
moisture lifting northeast ahead of it.

While at least some locally heavy amounts and an isolated threat
for flash flooding cannot to be ruled out within the deep moisture
pool that exists along and ahead of the entire extent of the low
level front, that stretches from the Northeast back through the
Ohio Valley and into the mid Mississippi Valley and Ozark region, a
greater risk for more widespread heavy rains and flooding concerns
is expected across some areas. This includes parts of the upper
Ohio Valley northeastward to central New York. Slow-moving training
cells, fueled by high PW anomalies (2-2.5 std dev above normal),
falling across relatively moist soils are expected to contribute to
a greater threat for flash flooding. Therefore, a Slight Risk
extending from parts of eastern Ohio to central New York was introduced.

...Northern Plains and Upper Midwest to the Central Plains...
A mid level trough will move across the northern Plains into the
upper Midwest this period. This will help a push a cold front,
extending from the northern Plains back into the central High
Plains further south and east. Moist southerly low level flow along
with increasing ascent will help support showers and
thunderstorms, with the models continuing to show a good signal
for organized storms developing and moving across portions of
Nebraska and South Dakota. While the generally progressive nature
of these storms is expected to limit the threat for widespread
flooding, intense rainfall rates may produce some areas of flash
flooding, especially across portions of eastern South Dakota and
Nebraska, southwestern Minnesota, western Iowa, and northwestern
Missouri. The HREF is showing some higher probabilities for amounts
over 2 inches, which along with relatively lower FFGs, indicates
that at least some isolated areas of flooding are possible.

...Southwest and Southern Rockies/High Plains...
Another daily round of showers and thunderstorms are expected to
develop and move east from the central New Mexico ranges into the
High Plains. Some isolated to scattered storms are expected to
develop further southwest across southeastern Arizona as well.
Isolated areas of flash flooding will remain a concern, especially
across burn scar, complex terrain, and poor drainage areas.

Pereira

Day 2
Valid 12Z Tue Jul 08 2025 - 12Z Wed Jul 09 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE NORTHEAST
AND MID ATLANTIC THROUGH THE TENNESSEE VALLEY, AND FROM THE UPPER
GREAT LAKES TO THE CENTRAL AND SOUTHERN PLAINS, AND ACROSS PORTIONS
OF THE SOUTHWEST, SOUTHERN ROCKIES, AND HIGH PLAINS...

...Northeast through the Tennessee Valley...
Deep moisture ahead of a slow-moving front will continue to provide
fuel for training storms and potentially heavy amounts as it slips
further south across the Northeast and the Mid Atlantic. Further to
the west the front is expected to return north ahead of a shortwave
moving into the lower Ohio Valley. A broad Marginal Risk was
maintained for now, however embedded upgrades to a Slight Risk may
be forthcoming in future issuances with the arrival of new
guidance. This may include portions of the Mid Atlantic to coastal
New England. The airmass will remain quite moist (PWs 1.75-2
inches), with some of the guidance indicating an uptick in
southerly low level inflow and moisture across the region.

Away from the front, the Marginal Risk was extended further south
to include portions of the eastern Carolinas. A lot of the guidance
shows a low level trough becoming the focus for deeper moisture and afternoon-developing, slow-moving storms. This may include some of
the areas impacted by heavy rains associated with Chantal.

...Upper Great Lakes to the Southern and Central Plains...
A mid-to-upper level shortwave will move out of the Mississippi
Valley and into the Great Lakes and lower Ohio Valley this period.
This will drive its associated frontal boundary and preceding
plume of deeper moisture further south and east across the region.
Similar to areas further east, a broad Marginal Risk was
maintained, recognizing that embedded Slight Risk area(s) may be
forthcoming if confidence increases as newer guidance arrives. One
potential area centers over the Ozark Region into the mid
Mississippi Valley, where deeper moisture and the ascent provided
by a mid level shortwave moving through the base of the broader
scale trough may generate more widespread heavier amounts.

......Southwest and Southern Rockies/High Plains...
Similar to the previous day, another daily round of showers and
thunderstorms are expected to develop and move east from the
central New Mexico ranges into the High Plains. Some isolated to
scattered storms are expected to develop further southwest across
southeastern Arizona as well. Isolated areas of flash flooding will
remain a concern, especially across burn scar, complex terrain,
and poor drainage areas.

Pereira

Day 3
Valid 12Z Wed Jul 09 2025 - 12Z Thu Jul 10 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE MID
ATLANTIC BACK THROUGH THE LOWER MISSISSIPPI VALLEY INTO EASTERN TEXAS...

An elongated axis of deep moisture will provide the corridor for
showers and storms, capable of producing locally heavy rainfall. A
well-defined shortwave moving out of Ohio Valley may provide the
focus for organized heavier amounts as it moves through the Mid
Atlantic on Wednesday. An upgrade beyond a Marginal may be
forthcoming if the models begin to show greater agreement and/or
back-to-back days of heavy amounts.

Pereira

$$
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FOUS30 KWBC 080920
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
520 AM EDT Tue Jul 8 2025

Day 1
Valid 12Z Tue Jul 08 2025 - 12Z Wed Jul 09 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF THE
EASTERN MID-ATLANTIC STATES AND SOUTHERN NEW ENGLAND, AS WELL AS
FOR PARTS OF THE ARKANSAS AND RED RIVER VALLEY AND ADJACENT OZARKS
AND OUACHITA MOUNTAINS...

...Mid-Atlantic and Northeast...
The remnants of post-tropical cyclone Chantal are in the process of transitioning into an open trough while exiting east of Cape Cod
to start the period, as it continues to get caught up in increasing southwesterlies downstream of a trough approaching from the Great
Lakes. This trough will continue to translate eastward through the
day, but will be slow to advect due to downstream Bermuda-type
ridging. Between these two features, southwest flow will remain
prevalent over the area, with 850-500mb winds being nearly
unidirectional from the W/SW at 15-20 kts. This will result in a
continued extremely moist environment with PWs likely eclipsing 2"
from eastern VA through southern New England Tuesday afternoon,
coincident with a plume of SBCAPE exceeding 2000 J/kg (per 00z HREF
mean fields).

Into these impressive thermodynamics, a subtle shortwave embedded
within the mean flow will traverse northeast ahead of a cold front
and along a surface trough, providing additional ascent atop the
already impressive convergence on these boundaries. The 00z hi-res
CAM consensus suggests showers and thunderstorms will become
numerous to widespread along and near the front during the mid to
late afternoon, and storm motions are expected to initially be
quite slow (0-1 km mean flow near 10 kts) with the potential for
localized backbuilding and training along the surface trough and
front (as Corfidi vectors collapse to around 5 kts with the
development of deep convection and resulting outflow boundaries).
With warm cloud depths potentially eclipsing 14,000 ft, this will
support efficient warm-rain processes and rain rates above 2"/hr
at times (and resulting localized hourly totals of 1-2"). Where
training occurs, this could result in total rainfall in excess of
3" (per 00z HREF 40-km neighborhood 3" exceedance probabilities
ranging from 10-40% across the SLGT risk area). Scattered
instances of flash flooding are possible across much of the I-95
corridor from Richmond, VA to Boston, MA.

...Southern Plains through the Ohio Valley...
A wavering front will press eastward from Oklahoma through Ohio
today, providing forcing for ascent through low-level convergence.
This frontal convergence will work in tandem with subtle height
falls as the driving trough pushes south and east, and modest PVA
as spokes of vorticity rotate eastward through the flow. While in
general this will result in scattered thunderstorms developing
along the front with rainfall rates of 1+"/hr, hi-res models have
come into better agreement in indicating a maxima of organizational
potential in the vicinity of the Ozarks and Ouachita Mountains (and
surrounding Arkansas and Red River Valleys). An inherited SLGT risk
in this region was maintained (and adjusted a bit based on the new guidance).

In this portion of the Southern Plains and into the Lower MS Valley,
a shortwave (and a mature/waning MCS) is digging southward this
morning, which may drive locally enhanced ascent and subsequent
initiation and organization of convection as early as this morning
through late afternoon/evening. PWs are already 1.8-2.0" in this
region, and a 20 kt LLJ is providing modest moisture transport with
500-1500 J/kg of SBCAPE already in place (forecast to increase to
as high as 2000-3000 J/kg with daytime heating, per 00z HREF mean
and ens max). While antecedent conditions are relatively dry (below
average rainfall over the past 7 days) with 3-hr Flash Flood
Guidance (FFG) ranging from 3-4", soil moisture is still indicated
to be generally well above normal (per NASA SPoRT 0-40cm and
0-100cm anomalies near or above 90th percentile) with streamflows
in the region near normal to above normal (per USGS data). The SLGT
risk generally encompasses where probs for localized 5" exceedance
are highest (per 40-km neighborhood probs from the HREF and
experimental REFS ranging from 20-30%).

Farther north near the base of the trough (into MO/IL), an MCV has
the potential to locally organize convection with better overall
dynamics (DPVA and shear from right-entrance region of jet streak)
compared to farther south (despite overall tropospheric moisture
likely to remain a bit lower with PWs less than 2.0" (but still at
or above 90th percentile). CAMs are not as aggressive with this
area, but will need to be monitored closely today given the MCV
and added daytime instability (HREF indicating SBCAPE rising to
1500-2500 J/kg).

...Upper Midwest...
A wave of low pressure and accompanying surface trough will move
progressively eastward from Minnesota into Michigan the first half
of today. While this will be generally fast moving, it will
impinge into a favorable environment to support heavy rain rates
which will likely eclipse 1"/hr, especially where it overlaps a
ribbon of MUCAPE reaching 1000-2000 J/kg. The fast motion will
limit total rainfall, but in some places that receive multiple
rounds of heavy rain, event totals could reach 2-3". This falling
atop sensitive soils (FFG as low as 1-1.5"/3hrs) could produce
localized instances of flash flooding.

......Southeastern New Mexico...
Another daily round of showers and thunderstorms is expected to
develop in the high terrain and then drop southeast into the High
Plains and southeastern portions of New Mexico. Although storms
are expected to be generally progressive as they come off the
terrain (0-6km mean winds from the north around 15 kts), they will
move into an axis of more favorable thermodynamics characterized by
PWs of above 1" and MUCAPE approaching 1000 J/kg. This could
support briefly heavy rain rates above 1"/hr, supporting an
isolated risk for flash flood impacts across urban areas or
sensitive terrain and burn scars.

Churchill/Weiss


Day 2
Valid 12Z Wed Jul 09 2025 - 12Z Thu Jul 10 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE EASTERN
MID-ATLANTIC STATES...

...Mid-Atlantic...
Quasi-stationary front from Tuesday will linger in a general east-
to-west fashion on Wednesday across the Mid-Atlantic States. Along
this boundary, a much more potent shortwave (likely enhanced in the
latest guidance from the aforementioned MCV currently in the
Plains) will press east within the approaching longwave trough,
leading to weak low pressure development moving east along this
front. The accompanying ascent will act favorably into continued
robust thermodynamics with PWs around 2 inches (above the 90th
percentile according to NAEFS ensemble tables) and 1000-3000 J/kg
SBCAPE during the afternoon. Increasing 0-6km bulk shear and
aligned 0-6km mean winds to the front suggests storms will
repeatedly develop to the SW and then train ENE across the Mid-
Atlantic states. Not only will this result in heavy rainfall which
may exceed 3 inches in some areas, but it will occur across primed
soils from heavy rainfall on prior days, enhancing the flash flood
risk. An inherited SLGT risk was maintained and expanded based on
the new guidance, and high-end (25%+) SLGT probabilities are
indicated from central NC through much of VA and into southern MD.
Upon the full evaluation of the new 12z CAM suite later today, a
targeted upgrade to MOD risk may be necessary for portions of the
SLGT risk (particularly given the more vulnerable antecedent conditions).

...Central Texas through the Southern Ohio Valley...
Stalled frontal boundary will gradually begin to lift northeast on
Wednesday over the OH Valley, but persistent ascent along this
front as weak shortwaves cross it will maintain a convective risk
through the day. Some DPVA and subsequent forcing for ascent from
storms in the Plains may be deflected southward into the warm,
moist air mass of the Southern Plains (possibly as far south as
more vulnerable areas of central TX). Storms will fire in response
to thermodynamics characterized by PWs around 2 inches collocated
with SBCAPE during peak heating that will approach 2000 J/kg. While
convection is likely to be scattered, any storm which trains along
the boundary with intense 1-2"/hr rain rates may result in rapid
runoff capable of producing instances of flash flooding (with training/repeating of efficient rates less likely into the Plains
and Lower MS Valley, but will come down to mesoscale details that
are difficult to discern in the 24-48 hour timeframe).

Churchill/Weiss


Day 3
Valid 12Z Thu Jul 10 2025 - 12Z Fri Jul 11 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
CENTRAL MID-ATLANTIC STATES, AS WELL AS FOR PORTIONS OF THE CENTRAL
PLAINS AND UPPER MIDWEST...

...Tennessee Valley into the Mid-Atlantic and New England...
A warm and anomalously moist air mass looks to remain in place
across much of the Southeast and Eastern U.S. into Thursday
continuing a broad flash flood threat into yet another day.
Although upper-level forcing looks less impressive overall relative
to Wednesday, still expect another round of primarily diurnally
driven convection focused along the terrain and associated leeward
trough of the Appalachians, perhaps becoming best organized a bit
farther south than prior days as the combination of best forcing
and moisture/instability looks concentrated across the southern
Mid-Atlantic into portions of the Southeast. Maintained an
inherited SLGT risk area for more vulnerable portions of central NC
and surrounding far south-central VA, but this area will likely be
modified over subsequent forecast cycles with dependencies on both
trends in the guidance and how the forecast ultimately pans out for
days 1 and 2 (as antecedent conditions will be a big factor). The
latest trends in the guidance suggest the threat will be more muted
from much of VA northward (with subtle height rises aloft from
sub- tropical ridging tries to offset the more favorable parameter
space for heavy rainfall).

...Northern and Central Plains into the Upper Midwest...
By Thursday the persistent ridge aloft over the Southwest U.S.
begins to break down, as an upper-low off the northern CA coast
opens up into a shortwave trough on Wednesday and ejects eastward
ahead of a digging longwave trough over western Canada. These two
features look to interact over the Northern and Central Plains, but
there are still substantial differences between models in how these
features evolve and interact. Maintained an inherited SLGT risk
area in the vicinity of where the best QPF signal overlaps (west-
central IA into adjacent portions of NE/SD/MN), but this area is
likely to shift over the coming days as models find a better
consensus of where organized convection is most likely to occur.
Regardless of where exactly this occurs, PWs of 1.5"+ are expected
(near or above 90th percentile for the region) with ample
instability and dynamics for organized convection and subsequent
high rainfall rates.

Churchill

$$
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FOUS30 KWBC 090930
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
530 AM EDT Wed Jul 9 2025

Day 1
Valid 12Z Wed Jul 09 2025 - 12Z Thu Jul 10 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE MID ATLANTIC...

...Mid-Atlantic and Southeast...

An anomalously moist and conditionally unstable air mass remains
entrenched across much of the eastern third of the CONUS, as a
pronounced mid-level trough extending from the Great Lakes to the
Mid-South gradually translates eastward. Height falls and DPVA from
this trough (along with increasing 0-6km bulk shear and enhanced
upper divergence from the favorable placement of a right-entrance
region of ~100 kt jet streak over New England) will coincide with
peak daytime heating and steep low-level lapse rates, eventually
resulting in widespread convective activity this afternoon across
much of the Mid-Atlantic (focused within the terrain and along the
leeward trough of the Appalachians) and into the Southeast (where a
TUTT cell is also playing a role, as some convection is already
ongoing early this morning in portions of southern GA and northern
FL). While much of the Southeast has been rather dry over the past
3-7 days, some portions of the Mid-Atlantic remain quite saturated
from prior days rainfall (and particularly from heavy rainfall in
association with Tropical Storm Chantal, which resulted in an area
of 4-10" of rainfall across central NC into south-central VA). A
Moderate risk was introduced with this forecast cycle for a
targeted portion VA (where flash flood warnings are even still in
effect at the time of writing from continuing convection
overnight), and this area represents the best overlap of
anticipated convective organization coinciding with vulnerable
antecedent conditions (as storms may be less organized farther
south where the bulk of rainfall occurred with Chantal, and
residence time may be too short farther north where stronger
dynamics will support the forward propagation of convection).

While the new Moderate risk area represents where more numerous
flash flood impacts are most likely to occur (with 00z HREF
neighborhood probabilities for FFG exceedance as high as 40-50%),
the Slight risk area has also been expanded fairly significantly to
encompass a large area from the Southeast (eastern GA into central
SC) into nearly all of the Mid-Atlantic (including the bulk of the
southern and central Appalachians) as PWs of 2.0"+ (near or above
the 90th percentile for much of the region) will allow for highly
efficient rainfall rates (with wet-bulb zero heights of 13-14k feet
allow warm rain processes to dominate) with localized totals of
1-3"/hr. Where these types of rates train/repeat, localized totals
of 2-5" are likely to occur (with the highest coverage of these
totals expected in and around the Moderate risk area). The threat
looks to be concentrated with peak daytime heating, mainly from
21-03z this afternoon and evening.


...Central Texas through the Southern Ohio Valley...

As the aforementioned mid-level trough crosses the OH Valley this
morning, a convective risk will be maintained for much of the day
from the Mid-South through the TN/OH Valley with elevated moisture
and increasing low-level lapse rates and instability from daytime
heating. Farther southwest into the Ark-La-Tex and central TX,
vorticity streamers from the trough are being shunted southwestward
(gradually rounding the persistent upper ridge over the Southwest)
and may help to locally organize convective activity. Elevated PWs
(generally between the 75th and 90th percentile) along with strong
daytime heating will result in generally scattered convection with
still efficient rainfall rates (up to 1-3"/hr) but limited coverage
and residence time resulting in isolated/localized totals of 2-4".
The Marginal risk was maintained and adjusted based on the new
guidance in this region.


...Central Plains into Mid-Mississippi Valley...

A shortwave rotating along the northern periphery of a ridge
centered over the Southwest U.S. will eject out of the northern
extent of the Front Range later today, leading to more focused
ascent and convective initiation portions of KS/NE into IA/MO by
later this afternoon/evening. While overall tropospheric moisture
and resulting rainfall rates are less impressive in this area,
there is some potential for upscale growth and convective
organization given increasing 0-6km bulk shear and steepening mid-
level lapse rates. While there is still considerable uncertainty
and hi-res model spread with the evolution and placement of higher
totals, HREF neighborhood probs suggest low-end chances (10-15%)
for localized 3" exceedance. This may bring a threat of isolated
flash flooding (which could go well into the overnight hours), and
the inherited Marginal risk area was adjusted accordingly based on
the new guidance.

Churchill


Day 2
Valid 12Z Thu Jul 10 2025 - 12Z Fri Jul 11 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
MID ATLANTIC...

...Tennessee Valley into the Mid-Atlantic and New England...

A warm and anomalously moist air mass looks to remain in place
across much of the Southeast and Eastern U.S. into Thursday
continuing a broad flash flood threat into yet another day.
Although upper-level forcing looks much less impressive overall
relative to Wednesday, still expect another round of primarily
diurnally driven convection focused along the terrain and
associated leeward trough of the Appalachians. Maintained an
inherited Slight risk area for more vulnerable portions of NC and
VA (from the Piedmont into the Coastal Plain) where the consensus
ensemble guidance signal remains highest for convective
organization (as vorticity streamers from the mid-level trough on
Wednesday may trail behind in the southern Appalachians long enough
to favorably support convective organization with peak daytime
heating on Thursday).


...Northern and Central Plains into the Upper Midwest...

By Thursday the persistent ridge aloft over the Southwest U.S.
begins to break down, as an upper-low off the northern CA coast
opens up into a shortwave trough on Wednesday and ejects eastward
ahead of a digging longwave trough over western Canada. These two
features look to interact over the Northern and Central Plains, but
there are still substantial differences between models in how
these features evolve and interact. PWs of 1.5"+ are expected
(near the 90th percentile for the region) with ample instability
and dynamics for organized convection and subsequent high rainfall
rates (as this shortwave trough looks much more potent relative to
the expected shortwave on Day 1). Maintained an inherited Slight
risk area that was adjusted based on the new consensus guidance.

Churchill


Day 3
Valid 12Z Fri Jul 11 2025 - 12Z Sat Jul 12 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE MID-ATLANTIC INTO THE SOUTHEAST, THE MID-MISSISSIPPI VALLEY
INTO THE MIDWEST, AND MUCH OF THE ROCKIES INTO THE CENTRAL AND
SOUTHERN HIGH PLAINS...

...Mid-Atlantic and Southeast...

As mid-level troughing becomes more established in the Northern
Plains into Day 3, ridging builds in response downstream and may
finally begin to suppress convection more significantly across the
northern Mid-Atlantic into the Northeast. While there are no clear
signs of significant convective organization at this juncture into
the Southeast and southern Mid-Atlantic, convective initiation with
scattered convection and locally high rainfall rates appears likely
(where ridging will be insufficient to fully suppress convection).


...Mid-Mississippi Valley into the Midwest...

More substantial convective organization is possible downstream of
shortwave troughs progressing/interacting in the Northern Plains
(placing the best risk more firmly into the Mid-MS Valley and Upper
Midwest). While the global ensemble guidance is coming into better
agreement with the QPF maxima, confidence is too low to introduce
a Slight risk with this cycle (with consensus guidance suggesting
1-3" totals, though so solutions suggest localized totals of up to
3-6" with inconsistent placement of the axis). Will continue to
evaluate with future cycles for the potential for an upgrade to
Slight risk.


...Rockies into the Central and Southern High Plains...

As the Southwest ridge continues to break down for a second day,
the global guidance signal for more substantial convective
initiation within the terrain of the Rockies increases into Friday
(and particularly so farther north into the northern/central
Rockies of WY/CO). Localized 1-2" totals (as indicated by both
downscaled deterministic GFS/ECMWF solutions and ensemble 1"
exceedance probabilities) in the sensitive terrain may lead to
localized flash flooding concerns, and more substantial convective
organization in association with shortwaves/vorticity maxima
rounding the ridge and coming off the terrain may allow for more
organized convection into the evening/overnight in the Central and
Southern High Plains.

Churchill

$$
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FOUS30 KWBC 100948
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
548 AM EDT Thu Jul 10 2025

Day 1
Valid 12Z Thu Jul 10 2025 - 12Z Fri Jul 11 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHERN NEW ENGLAND, THE MID ATLANTIC, AND THE CENTRAL PLAINS INTO
THE MIDWEST...

...Southern New England...

A Slight Risk was introduced overnight to portions of east-central
MA and surrounding portions of RI/CT, as highly anomalous moisture
(PWs near 2.0", near the 99th percentile per CFSR climatology) has
been supporting very efficient (but so far quite localized) hourly
rainfall totals of 1-2" (with as much as 1" in 15-min). This is
occurring on the northern/western periphery of an MCS tracking
that is tracking across southeast MA, supported by idealized
placement in the right-entrance region of a ~100 kt jet streak (at
250 mb) centered over northern New England/southern Quebec. While
the best low-level (925-850 mb) moisture transport with the LLJ is
located along/offshore with the MCS itself, this jet should veer
into the morning hours and allow for a short period of better
moisture transport into eastern CT/MA and RI. This should continue
the risk of scattered flash flooding at least a bit beyond 12z, as
RAP isentropic analysis indicates some of the best moisture
transport (isentropic lift/upglide) through the 925-700 mb layer
(295-305K isentropic surfaces). This upglide and resultant
slantwise instability may be sufficient to overcome a lack of
vertical instability for a period (though RAP analysis is still
indicating a bubble of 500-1000 J/kg of SBCAPE at 08z). The tail
end of this upglide may be positioned near the Boston metro area
between 12-15z, and some CAMs suggest the potential for localized
2-4" totals from these training showers (as indicated by both the
00z HREF and experimental RRFS PMM QPF fields). Given 3-hr FFGs in
the vicinity of Boston near 2.0", there may be a localized
instance of more significant flash flooding (primarily in more
vulnerable low- lying areas of the metro).

...Mid-Atlantic and Appalachians into the Southeast...

A shortwave trough situated over southern Quebec begins to lift
eastward today, but is slow to do so as it slogs through larger
scale ridging. Vorticity streamers trailing the upper trough may
allow for some convective organization today, though the highest
coverage and best rainfall rates are expected to be relegated to
southern portions of the Mid-Atlantic and into the Southeast (where
anomalous tropospheric moisture will also be on the downtrend, but
PWs still near 2.0" are around the 90th percentile per CFSR climo).
Ridging is expected to amplify in the wake of the departing SW, and
this will eventually result in height rises aloft that will be less
amenable to organized deep convection. As a result, expect a fair
bit less convective coverage today overall (particularly in more
northern portions of the Mid-Atlantic, perhaps with the exception
of the far northern Appalachians in NY/VT/NH where the closer
proximity of the lifting shortwave may provide better localized
uplift via DPVA and height falls with peak daytime heating). The
inherited Slight risk was generally maintained for much of VA/NC
and into SC (though the southern eastern portions of the Slight
have a greater risk of localized 5" exceedance, per 00z HREF
neighborhood probs near 10%, while the northern/western portions
are more sensitive with lower FFGs having had localized 3-5" totals
over prior days).

...Northern and Central Plains into the Upper Midwest...

Convective organization has been quite impressive overnight across
SD/NE/MN/IA, as storms tapped into the favorable left-exit region
of a subtropical jet streak (~90 kts at 250 mb) on the northern
periphery of an upper-level ridge that has been situated over the
Southwest U.S. and northwestern Mexico. The main shortwave
responsible for this jet streak has yet to move into the Plains,
but will do so today as it digs from the Intermountain West into
the Central Rockies and High Plains. Convection should fire once
again today, likely organizing and growing upscale over the Central
Plains with peak daytime heating this afternoon and evening. CAMs
suggest these storms may train favorably from west-to-east over
portions of NE/IA, while farther east an MCV from the storms
overnight will likely reinitiate convection with daytime heating
with the potential for backbuilding storms resulting in training
and repeating along a north/south axis from northwest IL through
southwest WI (though confidence in this scenario is a bit lower,
but has been impressively indicated for days by the ECMWF and its
accompanying AIFS solutions). PWs are generally near or above the
90th percentile across this whole region, though rainfall is badly
needed in some locations where moderate to severe drought is
present. Unfortunately too much rainfall too quickly may result in
scattered instances of flash flooding, as 1-2"/hr rates drive a
localized threat for 4-6" totals where storms are able to train and repeat.

Churchill


Day 2
Valid 12Z Fri Jul 11 2025 - 12Z Sat Jul 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER MUCH OF THE
UPPER MIDWEST AND INTO PORTIONS OF THE MID-MISSISSIPPI VALLEY AND
EASTERN CENTRAL PLAINS...

...Upper Midwest into Mid-Mississippi Valley...

Another shortwave trough is progged to dig southward from south-
central Canada into the Northern Plains, merging with the separate aforementioned shortwave that stalled out near the Central Plains
and Mid-Mississippi Valley. This will result in a much larger area
of organized convection on Friday and Friday night, and the best
axis looks to be positioned from central/eastern IA into southwest
WI (as this is the best model consensus and positioning of the
ECMWF and AIFS in particular, but there is still considerable
uncertainty with regard to the nuance of how these shortwaves
evolve/interact and where the highest totals ultimately fall).
Similar to Day 1, anomalous moisture (PWs of 90th percentile or
higher) looks to be in place prior to the arrival of drier, much
more stable air behind the accompanying cold front (which is
expected to sweep through the Northern Plains and into the Central
Plains and Upper Midwest late into the overnight). While much of
the rainfall will be beneficial for the region overall, the
inherited Slight Risk was expanded rather significantly. Future
targeted upgrades to Moderate Risk are possible, depending on what
transpires on Day 1 and how much overlap there is with additional
localized totals of 3-5" on Day 2.

...Appalachians and Mid-Atlantic into the Southeast...

As mid-level troughing becomes more established in the Northern
Plains into Day 2, and ridging/height rises build in response
downstream and may finally begin to suppress convection more
significantly across the Mid-Atlantic into the Northeast. While
overall intensity and coverage of convection should be drastically
lower compared to prior days, convective initiation is still
expected across the higher terrain of the Appalachians and along
the sea breeze of the Carolinas and bay breeze of the Chesapeake.
Some convection may propagate and/or initiate in areas inbetween,
and maintained a Marginal Risk as a result (also including areas of
the Southeast where slow moving, largely short-lived storms with
efficient rainfall rates of 1-3"/hr may present a localized flash
flood risk as well).

...Rockies into the Central and Southern High Plains...

As the Southwest upper-level ridge erodes tonight into early
Friday, there should be substantially more convective coverage
across much of the Rockies and into the Central and Southern High
Plains coincident with peak daytime heating. Organization looks
most likely over eastern CO and adjacent portions of WY/NE/KS, but
may propagate into the Southern High Plains as well (as northwest
flow becomes established with shortwave impulses rippling south,
getting tugged around the upper-level ridge retreating westward
towards Southern California). Localized 1-2" totals (which have
been continually indicated by both downscaled deterministic
GFS/ECMWF solutions and ensemble 1" exceedance probabilities) in
the sensitive terrain may lead to localized flash flooding
concerns. Should more substantial convective organization occur (as
the introduction of more CAMs seems to be indicating), then
localized 2-4" totals are possible (and may necessitate a Slight
Risk being introduced with subsequent outlooks).

Churchill


Day 3
Valid 12Z Sat Jul 12 2025 - 12Z Sun Jul 13 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER MUCH OF THE
SOUTHERN PLAINS INTO THE OZARKS...

...Southern Plains into the Ozarks...

Concerns are growing for more organized convection developing into
Day 3, stemming from a subtle shortwave/upper-level low forming and
stalling out over the Southern High Plains. The bulk of the global
guidance is now indicating this scenario, and the ECMWF suite
(including the ECENS and AIFS) are of particular concern with the
most robust signal of the models (with the AIFS indicating a
southward shift of best QPF signal, quite close to more sensitive
areas of central/North TX). A large Slight Risk was introduced to
encompass the area where organized convective activity is expected
to occur, though many of the details will still need to be ironed
out as we enter the hi-res CAM period. In the meantime, the
combination of already saturated soils and terrain sensitivities
across the broader region with highly anomalous tropospheric
moisture (PWs of 2.0"+ expected, near 90th percentile) is
justification for a broad Slight Risk that can be more fine tuned
in subsequent cycles.

...Upper Midwest, Great Lakes into Ohio Valley...

Convection should become less abundant into Day 3 in association
with the consolidated shortwave from Day 2, as it lifts into Canada
and forcing becomes less impressive overall (though still located
within a favorable right-entrance region of an attendant jet
streak). Daytime heating will likely drive the main threat with
short-term localized totals of 1-3" possibly resulting in isolated
flash flooding.

...Appalachians and Mid-Atlantic into the Northeast...

A broad Marginal Risk area continues into Day 3, as localized
downpours (1-2" hourly amounts) in association with daytime
heating present an isolated risk of flash flooding similar to the
prior day. Coverage and intensity may increase a bit, based on the
consensus guidance, but remains questionable as ridging aloft may
continue to tamp down on convection.

Churchill

$$
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FOUS30 KWBC 110814
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
414 AM EDT Fri Jul 11 2025

Day 1
Valid 12Z Fri Jul 11 2025 - 12Z Sat Jul 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE MID-MISSISSIPPI VALLEY AS WELL AS FOR PORTIONS OF THE CENTRAL HIGH PLAINS...

...Mid-Mississippi Valley...

A robust southwesterly low level jet streaming from the Plains into
the Mid-Mississippi Valley will provide a steady supply of Gulf
moisture into the region today. Meanwhile, a potent upper level
shortwave trough will approach this area from the west. The
combination of abundant moisture, instability, and forcing from the
shortwave will lead to numerous thunderstorms from northern
Missouri through eastern Iowa, northern Illinois, and far southern
Wisconsin, including the Chicagoland area. An MCS moving across
Iowa this morning will weaken in the morning daylight hours in
typical behavior for MCSs. Rainfall totals yesterday in the area
ranged from 1-4 inches, with the highest amounts across northern
Illinois west of Chicago. This rainfall has likely contributed to
saturating the soils in this area. Thus, the additional rainfall
forecast for this area should result in widely scattered flash
flooding. A higher-end Slight remains in place with only minor
changes from inherited, namely to trim up the southern end of the
Slight along the Kansas/Missouri border.

Showers and thunderstorms are likely to develop over central Iowa
as early as early this afternoon. As additional storms from in
northern Missouri, and track northeastward along the Mississippi
River, the potential for training storms will increase as the line
of showers and storms moves into northern Illinois. Backbuilding
may continue supporting additional thunderstorm formation as far
south as St. Louis this evening. This will likely allow the
potential for training storms to persist, increasing the flash
flooding threat.

...Central High Plains...

As a strong shortwave trough digs southeastward across the northern
Plains, divergence at the base of the trough will increase the
lift, supporting storms across northeastern Colorado this afternoon
and evening. Meanwhile, typical leeside troughing will support
thunderstorm formation immediately downwind of the Front Range,
generally between Cheyenne and Denver along I-25. Storms may
initially form as early as 22Z/4pm MDT. As the storms move east off
the Front Range, they will encounter increasingly favorable lift
from the shortwave, as well as some Gulf moisture tracking
northward up the Plains. This will allow the storms to organize and
grow upscale in coverage and heavy rain potential. It is in this
region near the Colorado/Nebraska/Kansas tripoint which will have
the greatest threat for flash flooding with some limited potential
for training. With very low FFGs, especially across northeastern
Colorado (1-1.5 in/hr), a Slight Risk upgrade was hoisted with this
update. Some of the guidance suggests the storms will persist well
into tonight generally across far northwestern Kansas, so the
Slight Risk area includes that area as well.

Wegman


Day 2
Valid 12Z Sat Jul 12 2025 - 12Z Sun Jul 13 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
SOUTHERN PLAINS...

As the northern stream shortwave that will bring heavy rainfall to
portions of the Midwest Friday pushes into the Great Lakes, the
southern end of that shortwave trough will get hung up across the
southern Plains. The trough will be supported by convection on the
nose of a potent LLJ transporting abundant Gulf moisture across
much of Texas and Oklahoma. This will allow a secondary shortwave
to develop, only moving very slowly across north Texas and Oklahoma
on Saturday. Early morning convection may be ongoing in the area at
the start of the period, which will likely weaken through the
morning. New convection will develop with typical peak afternoon
heating across north Texas and Oklahoma. Coverage and intensity
will peak across the area Saturday afternoon. Light and variable
steering flow will cause numerous storm interactions as clusters of
storms move in differing directions, greatly increasing the
likelihood for interactions between storms. Variability in the
placement of the storms is high in general, but there is some
agreement that by the overnight hours, the focus will be in far
northern Texas/southern Panhandle. This will likely keep the focus
of heaviest rain in the Childress/Wichita Falls area, generally
east of Lubbock and southwest of Oklahoma City. This area is in a
higher-end Slight, with considerable potential for a possible
Moderate Risk upgrade in the coming days, as this includes some
hard-hit areas from recent heavy rains.

There is considerable uncertainty as to exactly where the heaviest
and most persistent storms will form, but the general consensus is
to keep most of the rain north of the hardest hit areas of Kerr
County. That said, there are at least a few of the high-resolution
models suggesting heavy rain will get that far south, so the area
remains in a Marginal to Slight risk. Residents and first
responders should keep a close eye on the forecast over the next 24 hours.

Wegman


Day 3
Valid 12Z Sun Jul 13 2025 - 12Z Mon Jul 14 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
SOUTHERN PLAINS AS WELL AS FOR PORTIONS OF THE MID-ATLANTIC...

...Southern Plains...

A Slight Risk of excessive rainfall is in effect for many of the
same areas highlighted in the Day 2/Saturday ERO, for much of
northern Texas and Oklahoma. For now, rainfall amounts come down
quite a bit on Sunday as compared to Saturday. Thus, the flooding
potential will be significantly dependent on how the forecast
rainfall compares with Saturday, as well as how much rain actually
falls in the Slight Risk area on Saturday. Thus, for now, a Slight
Risk upgrade was introduced due to the likelihood for additional
strong thunderstorms in this area. Atmospheric moisture amounts
will increase on Sunday as compared with Saturday. The upper level
shortwave that forced the storms on Saturday will likely get left
behind and cutoff from the primary jet flow on Sunday. This slow
moving drift of the forcing should allow the storms to also remain
slow moving, and with increased moisture, the heavy rain potential
will very much still be in place on Sunday. Thus, there is some
expectation that forecast rainfall amounts in this area will
increase with time. Should this continue to be in the same area as
Saturday's storms, then it's likely additional upgrades will be
needed with future updates.

...Mid-Atlantic...

The shortwave that brought heavy rains across the Midwest on Friday
and Saturday will continue into the Mid-Atlantic and Northeast on
Sunday. By Sunday the shortwave will be lifting northeastward and
becoming more negatively tilted. This will increase the associated
divergence and lift. Meanwhile, plentiful Gulf/Atlantic moisture
will stream northward ahead of the shortwave, as PWATs in some
areas exceed 2 inches. This very high level of atmospheric moisture
will support a renewed round of heavy rain from strong
thunderstorms from the DMV north across much of Pennsylvania and
upstate New York. For New York, being both at the nose of the low
level jet and in the area of greatest upper level forcing will
further increase the likelihood for training heavy thunderstorms.
Meanwhile in the DMV, while overall coverage of storms will be
lesser, given the recent storms (and likely isolated to widely
scattered coverage both Friday and Saturday), a Slight Risk was
introduced for this portion of the Mid-Atlantic. The greatest flash
flooding potential will be up towards the eastern Finger
Lakes/Central New York, and additional upgrades in this area appear
likely, especially with low FFGs already in place.

Wegman

$$
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FOUS30 KWBC 120816
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
416 AM EDT Sat Jul 12 2025

Day 1
Valid 12Z Sat Jul 12 2025 - 12Z Sun Jul 13 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF THE
SOUTHERN PLAINS AND FOR PORTIONS OF NEW MEXICO...

A digging shortwave trough slowly moving across the Texas and
Oklahoma Panhandles and into Oklahoma tonight will act as a focus
for thunderstorms, as ample Gulf moisture streaming north across
the Southern Plains provides plentiful support for thunderstorms.
Much of the high resolution guidance suggests there will be 2
separate primary areas of thunderstorms today through tonight: One
will be along the TX/OK border, and a second one will be near or
over the Concho Valley, with a relative minimum of activity in
between. While this is the broader consensus, there is little
agreement on how those storms will evolve, including which areas
will be hardest hit with the heaviest rain. Given the sensitivity
for heavy rain in the Concho Valley especially, these prevalent
uncertainties support keeping the region in a very high end Slight
Risk for now. Since the bulk of the activity is expected tonight,
there remains at least one or two more forecast cycles before the
flooding rains get going over a broader area, so a Moderate Risk
upgrade remains quite possible with better agreement in the
guidance with future forecast cycles.

Neighborhood probabilities in the HREF guidance peak above 80% for
3 inches or more in a 40 km radius in much of the Slight Risk area
in Texas and Oklahoma. This lends credence to the high likelihood
that there will be flash flooding, but its magnitude and coverage
remains very low confidence.

Further west into New Mexico, the Slight Risk remains in effect
there to account for the sensitivities of communities in the
Sacramento Mountains north to the Sangre de Cristos. There is more
uncertainty here how any leeside storms will evolve, so here too
close attention will be needed for any potential targeted upgrades.

Wegman


Day 2
Valid 12Z Sun Jul 13 2025 - 12Z Mon Jul 14 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
SOUTHERN PLAINS AS WELL AS FOR PORTIONS OF THE MID-ATLANTIC...

...Southern Plains...

The upper level shortwave responsible for forcing the thunderstorms
from Saturday night will cut off from the primary flow with the jet
on Sunday, This upper level shortwave will coincide with a
stationary front over Northwest Texas and Oklahoma. There will be a
continuous southerly flow of plentiful Gulf moisture across Texas
and Oklahoma on Sunday, but with limited forcing, the overall
coverage of showers and thunderstorms will be lesser on Sunday as
compared with D1/Saturday. The tradeoff in some areas with this
setup is because both the stationary front and upper level cutoff
disturbance will be very slow-moving, if moving at all, some of the
same areas that will likely see heavy rain from thunderstorms for
the second consecutive day. This is most likely in north-central
Texas and southeastern Oklahoma. For this reason, a higher end
Slight is in effect for this area. While storm coverage will be
lesser, due to the abundant moisture available for any storms, the
stronger storms will be capable of 2+ inch/hour rainfall rates,
which over sensitive areas will be plenty heavy enough to cause
localized flash flooding. Should the rainfall in this area
overperform on D1/Saturday, with better agreement in the high
resolution guidance, then it's possible a Moderate Risk upgrade may
eventually be needed. The chances of an upgrade are lower during
this period as compared with D1/Saturday.

...Mid-Atlantic...

Very few changes were needed to the Slight Risk that covers much of
the central Appalachians from Virginia north through upstate New
York. Abundant Gulf and Atlantic moisture will stream north up the
East Coast through the period, increasing PWATs locally to over 2
inches. A potent cold front will cross out of the Midwest and into
Pennsylvania and New York Sunday night. This forcing will result in
numerous showers and thunderstorms capable of very heavy rainfall
in the Slight Risk area. The greatest rainfall totals are likely
from northern Pennsylvania through central New York. Further south
towards the DMV, while forcing will be lesser, any storms that
form will be capable of heavy rainfall with abundant moisture available.

Wegman


Day 3
Valid 12Z Mon Jul 14 2025 - 12Z Tue Jul 15 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF THE
CENTRAL AND SOUTHERN FLORIDA PENINSULA...

A westward-moving tropical wave will move across the Florida
Peninsula on Monday, with the greatest rainfall and threat for
storms expected during peak heating Monday afternoon. PWATs with
the wave will be over 2.25 inches in south Florida. While there
remains considerable uncertainty as to convective evolution and
placement, the sheer volume of moisture available for any storms to
draw upon in the formation of heavy rain will be more than capable
of supporting heavy rain and resultant flash flooding. Much of
Florida has been dry for soil moisture and recent lack of rainfall,
so the drier than normal conditions will likely mitigate any
potential flash flooding. Urban areas such as the Miami-Ft
Lauderdale metro as well as Tampa and Orlando will be at a higher
risk for flash flooding due to the slow-moving storms, which will
likely interact via cold pools through the afternoon. The Slight
Risk upgrade was coordinated with TBW/Tampa, FL, MLB/Melbourne, FL,
and MIA/Miami, FL forecast offices.

Wegman

$$
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FOUS30 KWBC 131108
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
708 AM EDT Sun Jul 13 2025

Day 1
Valid 12Z Sun Jul 13 2025 - 12Z Mon Jul 14 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE TEXAS HILL COUNTRY...

...Southern Plains...

11Z Update: Assessment of the current radar and observation trends
the last few hrs. gave enough credence to upgrade a portion of the
Texas Hill Country to a Moderate for locally significant impacts.
Heavy convection is ongoing across the Lower Concho Valley through
Central TX with much of the activity slowly progressing east-
southeast along outflow generation. Cold pool convergence and mean
wind aligning parallel to the flow have likely exacerbated some
repeating convective patterns over the area above, as mentioned in
the forecast update overnight. This trend will allow for
approximately 2-4 more hrs. of heavy rainfall in the area before
the threat wanes with diurnal mixing and LLJ weakening over the
region. The Moderate Risk is now in place for at least the front
end of D1 with a reassessment later this morning on any
changes/realignments for the remainder of the period (beyond 16z).

Kleebauer

..Previous Discussion..

Sunday morning begins and it is likely that convection, some of
which will be strong with heavy rainfall rates, will be ongoing
across parts of Texas. This will be in response to a potent and
convectively enhanced shortwave/vorticity maxima that will be
pivoting across the state. This shortwave will be embedded within a
weakness in the mid-level pattern between ridges both to the west
and east, basically becoming trapped within a weak col across
Texas. As the day progresses, this vorticity maxima should become
strung out and aligned more SW to NE as the mid-level trough axis
tries to swing eastward. While this will likely push some PVA
northeast into Oklahoma and the Ozarks, a ribbon of vorticity may
remain trapped back across Texas, leading to a corridor of enhanced
ascent, aided by at least modest upper diffluence during the
afternoon as a weak jet streak pivots across the middle of the country.

At the surface, this trough axis will attempt to push a surface cold
front beneath it steadily to the east. However, it is likely this
front will oscillate a bit north and south in response to varying
and increasing low-level flow. Low-level return flow out of the Gulf
will gradually veer from SE to SW, reaching 15-25 kts, and pushing
PWs to as high as 2 inches. This anomalous moisture (PW anomalies
+1.5 to +2 sigma according to the GFS) will merge into the wavering
front, causing its oscillatory behavior, while additionally
transporting more impressive MUCAPE northward through the day and
night (reaching above 2000 J/kg at times).

With forcing for ascent remaining robust through the period, this
will result in waves of convection generally along the front, but
the CAMs are generally scattered as to where the heaviest rainfall
will occur due to differences in frontal placement and the weak
mid- level impulses. However, the impressive thermodynamics in
place will support heavy rain rates that will likely (>50% chance)
exceed 1"/hr, with short term rates of 3-4"/hr possible at times.
Utilizing both the HREF and REFS ensembles, the greatest chance for
more than 3" of rain appears to be focused from the Hill Country
of Texas northeast into the St. Louis, MO metro area, and the
slight risks have been adjusted from inherited in these areas.

There continues to be a signal in the guidance leading to a
somewhat higher potential for flash flooding across portions of
the Texas Hill Country northeast towards the Dallas metroplex. HREF
and REFS probabilities for 5"/24hrs peak around 30-40% in this
region, and this will be on top of heavy rain that is occurring
overnight (before 12Z Sunday). Briefly considered a MDT risk but
uncertainty in coverage and placement prevents that at this time.
However, there could be some locally significant impacts across
this area if slow moving convection can move effectively across the
more vulnerable areas, and it is possible a D1 upgrade to a MDT
risk may be needed depending on how convection evolves through the
early morning hours.

...New Mexico...
Farther to the west, the westward periphery of the
PW plume emerging from the Gulf will spread into New Mexico,
spreading PWs above 1" (+1 sigma) into the High Plains and into the
terrain of the central part of the state. This PW will overlap with
a ribbon of MUCAPE around 2000 J/kg to support scattered to numerous thunderstorms developing during peak heating over the higher
terrain. These storms will initially move slowly on 0-6km mean winds
of just 5 kts, but the presence of 20-25 kts of bulk shear will
help drive modest organization as storms come off the terrain and
drift southward on Corfidi vectors around 10 kts. With rain rates
above 1"/hr likely, this could result in instances of flash
flooding, especially over sensitive terrain features, urban areas,
or burn scars.

...Mid-Atlantic into the Northeast...
Mid-level ridge gradually pulsing northward from the Gulf Coast
will interact with a broad and slow moving trough advecting across
the Great Lakes to produce pinched SWly flow across much of the
eastern CONUS. This will manifest as impressive thermodynamics
being drawn northward from the Mid-Atlantic into interior portions
of the Northeast. These thermodynamics will be characterized by PWs
of 1.75 to 2.0 inches (90th - 99th percentile according to NAEFS)
and collocated MUCAPE of 1000-2000 J/kg to produce an environment
favorable for heavy rain. Into this environment, a cold front,
pushed slowly eastward by the mid-level trough to the west, will
combine with slow height falls to drive pronounced ascent, creating
scattered to numerous thunderstorms from the eastern Ohio Valley
into Northern New England.

These storms will contain heavy rain rates that have a 30-50% chance
of exceeding 1"/hr with brief 2+"/hr rates also possible. Although
bulk shear is progged to be minimal such that convection will
generally remain of the pulse variety, brief training as 0-6 km mean
winds aligns to the front will allow for some longer duration of
this heavy rainfall in a few areas, leading to HREF and REFS 24-hr probabilities that peak above 70% for 3". While it is difficult even
at this time range to identify the areas most at-risk to flash
flooding due to uncertainty in exact convective placement, 0-10cm
soil moisture is above the 90th percentile according to NASA SPoRT
from central VA through Upstate NY, which is also collocated with
the locally higher ensemble probabilities. This suggests that the
inherited SLGT risk is warranted, and only adjusted cosmetically
for new guidance, although there is a signal in the guidance for
some locally heavier rainfall across the Finger Lakes region of NY
due to repeating/backbuilding cells which could result in some
locally more substantial impacts.

...Florida...
Slow moving 500mb trough east of Florida will strengthen gradually
as it drifts W/SW today. The accompanying vorticity maxima will
provide some locally enhanced forcing to the eastern side of FL,
while the entire peninsula remains sandwiched between this and a
ridge to the west, producing northerly flow across the area. As the
vort swings westward, some locally enhanced diffluence will
develop aloft as well, and as this occurs in the presence of PWs
above 2 inches collocated with MUCAPE of 2000-3000 J/kg, widespread
convection with heavy rain will result. CAMs suggest storms will
fire on the E/NE side of the peninsula and then drift SW, with some
locally enhanced organization possible into clusters thanks to
20-30 kts of bulk shear. With rain rates progged by the HREF to
have a 30-50% chance of exceeding 2"/hr, this could result in total
rainfall of 3-4", locally higher, as suggested by 24- HREF/REFS
probabilities and PMM. Where this rain occurs over more urban
areas, local flash flooding could result.

Weiss


Day 2
Valid 12Z Mon Jul 14 2025 - 12Z Tue Jul 15 2025

..THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE
FLORIDA PENINSULA AND PORTIONS OF THE MID-ATLANTIC STATES...

...Florida...
The westward-advancing and deepening mid-level wave will reach the
FL peninsula on Tuesday, providing widespread increasing ascent
across the state. In addition to the height falls/PVA accompanying
this trough, modest upper diffluence will develop as northerly flow
continues, enhancing deep layer lift. This impressive and
amplifying ascent will impinge into intensifying thermodynamics
with PWs surging above 2.25 inches, or above the 90th percentile
according to NAEFS. There continues to be some evolutionary
discrepancies among the various models, but in general the setup
will be favorable for widespread thunderstorms with heavy rainfall,
especially during peak heating when MUCAPE climbs above 2000 J/kg.
The heaviest rainfall will again likely develop across the NE
portion of the peninsula, similar to Sunday, and then track SW
along outflows and any weak low-level convergent boundaries. With
rainfall rates likely eclipsing 2"/hr, some bulk shear 20-30 kts to
help organized convection into clusters, and chaotic/weak storm
motions, total rainfall could exceed 3" in places again on Monday.
The inherited SLGT risk was adjusted slightly, but in general
remains as inherited and over the greatest ensemble probabilities
from the HREF, SREF, and ECMWF EFI.

...Mid-Atlantic States...
A cold front will gradually traverse southeast across the Mid-
Atlantic and Northeast on Monday, with thunderstorms likely
developing along it during the afternoon and evening. This front
will be pushed eastward downstream of an advancing, but weakening,
mid-level trough axis, with the resultant and lingering strung out
vorticity helping to provide additional ascent along the boundary.
This ascent will work into thermodynamics that will be extremely
supportive to heavy rain within thunderstorms, as broad return flow
ahead of the front (SW at 10-15 kts) draws a ribbon of PWs above 2
inches (above the 90th percentile according to NAEFS) and
collocated MUCAPE over 1000 J/kg into New England. This will also
be an area where warm cloud depths are progged to reach extreme
values above 15,000 ft, supporting efficient warm-rain processes
which have a 40% chance of exceeding 2"/hr according to the HREF,
especially in the Mid-Atlantic.

While heavy rain rates are expected within any convection along
this advancing front, in general, storms should be more progressive
with greater latitude. However, there is a signal in the available
guidance for some convection to develop ahead of the front and then
backbuild into the greater thermodynamics across the Mid-Atlantic
region leading to some locally higher ensemble probabilities for
3"/24hrs and a modest but notable ECMWF EFI signal. This area has
also been wet the past 7 days, and soil infiltration capacity is
limited (FFG as low as 1-1.5"/3hrs). For these reasons, a SLGT risk
has been added for Monday, with urban areas and most sensitive soil
regions of VA/MD/PA favored for the greatest potential for
excessive rainfall.

...Desert Southwest through the Ozarks...
The same cold front moving into the Mid-Atlantic Monday will sag
southward but weaken and dissipate across the Southern Plains as it
interacts with slow height rises as a ridge slowly builds from the
south. Despite the weakening front, ascent will remain as a
shortwave and accompanying strung-out vorticity drift over the
area, especially near the Ozarks as it gets trapped within a col
between neighboring high pressures. There will also likely be
other modest vorticity impulses rotating through the flow into the
Southwest to additionally provide locally targeted ascent.

This lift will work into a still very favorable environment to
support heavy rainfall as PWs remain nearly 2 inches into the
Ozarks and above 1" as far as southern Arizona thanks to persistent
moist advection out of the Gulf leading to PW anomalies reaching
above the 90th percentile locally from West TX into NM and near the
Ozarks. These are the locations that may have slightly higher
potential for excessive rainfall on Monday, with slow moving storms
over West Texas/New Mexico (0-6km mean winds 5 kts or less) and
organized convection on 20-30 kts of bulk shear from OK into MO/AR.
However, at this time, despite some modest signals for a locally
enhanced flash flood risk, the MRGL risk remains as confidence is
not higher enough for an upgrade at this time.

...Northern Plains...
Potent but positively tilted shortwave will dig out of British
Columbia and emerge into a belt of pinched westerlies aligned to
the Canada/United States border. This will help elongate a cold
front as it drops southward into the Northern Rockies and Northern
High Plains, producing locally enhanced ascent across the area. A
piece of this vorticity lobe will swing rapidly eastward and
interact with the low-level baroclinic zone, which will intensify
due to warm advection on an 850mb LLJ surging to 30 kts Monday
evening up the Plains, drawing thermodynamics characterized by PWs
of 1-1.25 inches and MUCAPE of 1000 J/kg northward. This will
support scattered thunderstorms Monday night, and although cells
should remain progressive on 0-6km mean winds of 20-25 kts, aligned
Corfidi vectors to the mean wind and the front suggests training
which could produce 1-2" of rainfall and local FFG exceedance.

Weiss
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FOUS30 KWBC 180815
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
415 AM EDT Fri Jul 18 2025

Day 1
Valid 12Z Fri Jul 18 2025 - 12Z Sat Jul 19 2025

...THERE IS A MODERATE RISK FOR EXCESSIVE RAINFALL FOR THE NORTHERN
SHENANDOAH VALLEY OF NORTHERN VIRGINIA...

...Mid-Atlantic...

The biggest changes for today's outlook were made across the Mid-
Atlantic. Abundant moisture that has been in place across much of
the Mid-Atlantic for at least the past week will only build today
as a steady supply of deep tropical moisture from the Gulf pushes
northeastward across the South and into the Mid-Atlantic. This
moisture will contain ample instability for storms to draw on as
MUCAPE values exceed 3,000 J/kg across much of VA and points south.

The primary forcing will be a back door front of sorts, though it's
more of a dry line. The front will gradually sag southward, making
the most southward progress down the coast. Thus, the front will
become more northwest-to-southeast oriented with time. The front
acting as a focal point for lift will allow widespread shower and
thunderstorm activity to develop across West Virginia as early as mid-to-late-morning. As these storms progress eastward, they will
encounter areas that have been hard-hit with heavy rain and
therefore have swollen streams and creeks and saturated soils, such
as in the northern Shenandoah Valley. After the first round of
storms moves through around midday or so, additional storms will
quickly develop behind it over the northern Shenandoah Valley and
then they too will push southeastward, gradually organizing into
clusters and lines of storms. The likelihood for the northern
Shenandoah Valley to act as a focus for the storms to initially
develop and organize has increased markedly with the latest
guidance. HREF probabilities of exceeding 3 and 6 hour FFG values
are over 70% through the late afternoon. This is in significant
part due to the aforementioned saturated soils across the area.
Further, neighborhood probabilities of exceeding 3 inches of
rainfall are over 70% for the afternoon period, and over 25% for
exceeding 5 inches of rain. Much of that rain will fall with the
heaviest storms, as local rainfall rates may exceed 3 inches per
hour at times.

For these reasons, in coordination with LWX/Sterling, VA forecast
office, a Moderate Risk upgrade was introduced with this update for
the I-81 corridor in the northern Shenandoah Valley, which includes
the westernmost portion of I-66. Elsewhere, the Slight Risk was
expanded north and west with the latest guidance suggesting morning
convection will impact far northern West Virginia, and likely train
as it moves into far western Maryland. Recent rainfall and the very
flashy nature of the streams and creeks in that area also support
the Slight Risk upgrade in these areas.

...Gulf Coast...

The tropical disturbance centered near New Orleans and Lake
Pontchartrain at the time of this writing continues to produce
very limited shower and thunderstorm activity well to its west over southwestern Louisiana. Over the next few predawn hours,
thunderstorm activity is likely to markedly increase both east and
west of the center of circulation. To the west, the northerly flow
west of the center will collide with the broader southerly flow
over much of the rest of the Gulf, likely leading to a localized
convergence zone near the southwestern Louisiana coast. This will
result in a localized maximum of rainfall in that area. Meanwhile
to the center's east, the complimentary southerly flow over the
Gulf and east of the center will support strong advection of deep
tropical moisture. North-south oriented lines of cellular
convection will developing also likely near the coast, where
frictional convergence increases. These lines are likely to remain
nearly stationary since the center of circulation will be moving
nearly due north, so the forcing from the low center will remain
steady state. For these reasons, the Slight Risk in the ERO was
maintained largely unchanged, though there will likely be a minimum
of thunderstorm activity in between these two maxima in eastern
Louisiana. Despite this minimum, the abundance of tropical moisture
present will still support isolated to widely scattered convection
near the center which will be very capable of embedded heavy rainfall.

...Midwest...

The nose of a potent southwesterly LLJ will intrude into the Iowa/Minnesota/Wisconsin area through the day today. As an upper
level shortwave digs south out of the jet over northern Minnesota,
the front at the nose of the LLJ will act as a focal point for
strong thunderstorms. PWATs will increase above 1.75 inches over
the area, which will supply plentiful fuel for the thunderstorms to
produce cells of heavier rainfall as they track southeastward along
the front. The LLJ will support backbuilding and training storms as
the moisture and instability supply with the LLJ remains in place
to allow for additional thunderstorm development behind any initial
line of storms. As the storms move into the instability, expect any
initial clusters to organize into one or two lines of storms as
they press into Iowa. Due to the potential for heavy rain and
recent heavy rainfall having partially saturated the soils in the
area, the Slight Risk remains in place across the region,
particularly for the localized areas where storms train and
backbuild. The rather fast movement of the storms should somewhat
limit the flash flooding potential, so the area remains a lower end Slight.

...Southwestern New Mexico...

A tongue of higher moisture across southwestern New Mexico today
will act as a focus for widespread shower and thunderstorm activity
this afternoon with maximum daytime heating. The showers and storms
will be capable of locally heavy rainfall, though PWATs only around
1.25 inches may limit the overall coverage of any heavier
convection. The storms may organize around any local terrain
features. Local burn scars and shallow soils will both contribute
to potential flash flooding as the rainfall quickly flows into the
local streams and rivers. The Slight was left unchanged from
inherited as guidance remains in good agreement on the location of
the highest flash flooding potential.

...Eastern Nevada...

The Slight Risk area across eastern Nevada and a sliver of Utah
also remains unchanged with this update. A slow, northward moving
upper level low will help concentrate the available atmospheric
moisture in the area to allow any storms that form with afternoon
heating to persist and perhaps organize into a slow-moving line of
storms by the evening hours. The Slight Risk area was unchanged
from the previous update in this area.

Wegman


Day 2
Valid 12Z Sat Jul 19 2025 - 12Z Sun Jul 20 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
MIDWEST INTO THE TENNESSEE VALLEY AND THE SOUTHERN MID-ATLANTIC...

Ample tropical moisture, at least in part associated with the plume
of moisture associated with the low over Louisiana will stream
northeastward on a continuous low level jet. As that moisture runs
into a stationary front set up over the Midwest, it will be lifted,
resulting in numerous showers and thunderstorms all across the
region. The guidance is in poor agreement as to how those
thunderstorms will organize. What appears most probable is the
cluster of thunderstorms from the upper Midwest on Day 1/Friday
will continue southeastward along the front, able to easily sustain
itself due to the abundant tropical moisture in place across much
of the eastern half of the US.

With daytime heating, clusters of showers and thunderstorms will
develop ahead of this aforementioned line. Cell mergers and the
eventual congealing of the storms with the line will allow quite a
few areas across the Midwest to have multiple rounds of storms to
impact the area. This will likely result in widely scattered to
scattered instances of flash flooding. Areas hard hit with heavy
rainfall in previous days would be particularly vulnerable to
additional flash flooding should multiple rounds of storms move
over those communities.

Wegman

Day 3
Valid 12Z Sun Jul 20 2025 - 12Z Mon Jul 21 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
MIDWEST AND NORTHERN PLAINS...

...Midwest...

A complex setup looks to unfold across this region on Sunday. A
line of storms will move southeastward from the Mississippi River
Valley across the Ohio Valley. With ample daytime heating and a
stationary front still in place. Widespread thunderstorms will
develop along the frontal interface. The storms will interact with
each other, likely congealing into clusters as the line absorbs the
storms from northwest to southeast. Behind this line however,
additional storms are likely to develop overnight Sunday night,
especially for western areas in Iowa and Illinois. The slow moving
nature of the storms at the nose of the jet will increase the flash
flooding threat in that region as well. Further, all of the Slight
Risk area will have been through storms from the Day 2/Saturday
period, so soils are likely to be more responsive to flash flooding
should storms occur in these same areas again on Sunday. There is
some uncertainty as to where the storms will align, which will
depend on frontal position. Much of the guidance has trended a bit southwestward, so the Slight was trimmed out of northern Indiana
and Illinois with this update in favor of the central portions of
those same states. Into Kentucky and the western Virginias, terrain
and recent heavy rainfall increase the flash flooding threat
further in these areas, where a higher end Slight remains in effect.

...Northern Plains...

Much of North Dakota will be at the nose of a potent low level jet
across the area. A subtle shortwave in the upper level jet may be
all it takes to initiate a line of storms across the region,
especially Sunday night, though there may be two separate rounds:
one in the morning and a second Sunday night. There is considerable
uncertainty both with storm intensity and receptivity of the ground
to the heavy rainfall. Due to this uncertainty, the Slight Risk
area was left unchanged with this update, but is considered a lower end Slight.

Wegman
$$
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FOUS30 KWBC 190750
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
350 AM EDT Sat Jul 19 2025

Day 1
Valid 12Z Sat Jul 19 2025 - 12Z Sun Jul 20 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE MIDWEST, THE MID-SOUTH, THE SOUTHERN MID-ATLANTIC STATES, &
THE SOUTHERN APPALACHIANS...

Corn Belt/Ohio Valley/Mid-Atlantic States/Mid-South...
Ample moisture exists regionally. Some of this is due to the
synoptic pattern, with the Westerlies stronger than and south of
July norms which is allowing for greater effective bulk shear and
thunderstorm organization. Some of the moisture influx is also due
to the flow around the retrograding 3 sigma warm core ridge for
mid- July moving into the eastern Gulf. Additional moisture is
being imported from the direction of the former tropical
disturbance. Regardless of the source, precipitable water values
are forecast to crest at or above 2.25". ML CAPE could exceed 4000
J/kg due to daytime heating. Portions of IA, IL, and KY have the
potential for backbuilding convection both Saturday morning and
Saturday night/Sunday morning. Across IA, there is a question about
how much overlap convection dropping in from the north this
morning would have with convection Saturday night/Sunday morning.
Within such an environment, hourly rain amounts to 4" are possible,
with local amounts to 8". At the moment, these amounts are not
explicitly forecast by much of the guidance, with the 00z HREF/18z
RRFS showing minimal potential for 5"+ amounts, centered across IA.
However, the high resolution NAM and Canadian Regional show local
totals in the 6" ballpark. Large swaths of the region have had
well above average rainfall during the past week, saturating soils.
Since there's a bit of uncertainty, coordination with DMX/Des
Moines IA and DVN/Davenport IA have left the risk area as a high-
end Slight. However, should cells train for 2+ hours downstream of
existing instability pools, localized Moderate or High Risk
impacts cannot be ruled out.

Southwest/Southern Rockies...
Enough moisture is available for scattered monsoon convection again
on Saturday. Hourly amounts to 2" are possible due to diurnal
heating, which would be most problematic in urban areas, dry
washes/arroyos, or burn scars.

Roth


Day 2
Valid 12Z Sun Jul 20 2025 - 12Z Mon Jul 21 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
MIDWEST, SOUTHERN APPALACHIANS, & NORTHERN PLAINS...

...Midwest, Ohio Valley, & Southern Appalachians...
High moisture for Saturday persists into Sunday -- precipitable
water values eclipsing 2.25" -- with the core of the instability
pool more significant across portions of the Ohio Valley on Sunday
as warming at 700 hPa occurs across the Central Plains, slowly
strengthening a mid-level capping inversion. Effective bulk shear
should remain sufficient for convective organization. Inflow off
the instability pool could lead to backbuilding, so the potential
for 4" amounts in an hour and local 8" totals remains (the 00z NAM
advertised 7"). There's not enough confidence on where the higher
amounts will materialize to upgrade to a Moderate Risk, but a
higher end Slight Risk appears to exist from in and near southern
IL into KY, TN, southern WV, and westernmost VA. Localized Moderate
or High Risk impacts cannot be ruled out.

...Northern Plains...
Much of North Dakota will be at the nose of a potent low level jet
across the area. A subtle shortwave in the upper level jet may be
all it takes to initiate a line of storms across the region,
though there may be two separate rounds: one in the morning and a
second Sunday night. There is considerable uncertainty both with
storm intensity and receptivity of the ground to the heavy
rainfall. Used the recent guidance to trim some of the Slight Risk
area away. Like continuity, believe this is a lower end Slight Risk.

Southwest/Southern Rockies...
Enough moisture is available for scattered monsoon convection on
Sunday. Hourly amounts to 2" are possible due to diurnal heating,
which would be most problematic in urban areas, dry washes/arroyos,
or burn scars.

Roth/Wegman


Day 3
Valid 12Z Mon Jul 21 2025 - 12Z Tue Jul 22 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTHERN ROCKIES, PLAINS, OHIO VALLEY, & SOUTHEAST...

Surface boundaries/low pressure areas/upper level disturbances are
on this move this period, which along with warming temperatures at
700 hPa/increased mid- level capping across portions of the
Central Plains and IA should broadly limit QPF and flash flood
potential. Wherever cells can manage to train/merge, hourly rain
amounts up to 3" with local totals to 6" would be possible across
the Plains, Ohio Valley, and Southeast, while hourly amounts up to
2" and local totals to 4" would be possible across the Southern
Rockies and Southwest. At the moment, it appears any flash flooding
would be on an isolated to widely scattered basis. In the
Southwest and Southern Rockies, burn scars and dry washes/arroyos
would be most at risk. Anywhere within these regions, urban areas
would be of most concern.

Roth

$$
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FOUS30 KWBC 200738
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
338 AM EDT Sun Jul 20 2025

Day 1
Valid 12Z Sun Jul 20 2025 - 12Z Mon Jul 21 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL IN AND NEAR
CENTRAL ILLINOIS...

...Midwest, Ohio Valley, & Southern Appalachians...
High moisture persists into Sunday -- precipitable water values
eclipsing 2.25" -- with the core of the instability pool more
significant across portions of the Ohio Valley on Sunday as warming
at 700 hPa occurs across the Central Plains, slowly strengthening
a mid-level capping inversion. Effective bulk shear remains
sufficient for convective organization, including mesocyclone
formation. Two rounds of convection are expected -- a morning round
dropping out of IA into the Midwest and Ohio Valley with a second
round forming in the vicinity of northeast KS during the afternoon
and evening hours. Of some concern is the backing of the low-level
winds during the 18-00z time frame, which could act to anchor any
existing convection in place/limit forward propagation. Any complex
that forms in northeast KS and northern MO is expected to spill
into portions of IL during the evening and overnight hours late
this day (into early Monday morning). Considering the degree of
moisture, instability, and effective bulk shear, there is the
potential for 3-4" amounts in an hour and local 8" totals. The
guidance has increased its signal for higher amounts with a few
pieces of guidance advertising 8-11" of rain in the 00z model suite,
so in coordination with LSX/St Louis MO, ILX/Central IL, and
IND/Indianapolis IN forecast offices, added a Moderate Risk area
in and near central IL. Localized High Risk impacts cannot be
ruled out should any training bands or cell backbuilding persists for 3+ hours.

To the southeast of the Moderate Risk area, a higher end Slight
Risk appears to exist for much of the rest of the Ohio Valley and
western slopes of the Southern Appalachians, with some guidance
showing a secondary maximum between eastern KY and the KY/OH/WV
border junction. Lingering model uncertainty kept us from upgrading
to a Moderate Risk for the possible secondary maximum. With the
same rainfall potential -- hourly amounts to 3-4" with local 8"
totals possible -- localized Moderate Risk impacts cannot be ruled out.

...Northern Plains...
The Dakotas/MN will be at the nose of a modest low level jet. A
shortwave moving by the area may be all it takes to initiate a
line of storms across the region, though there may be two separate
rounds: one in the morning and a second Sunday night. The guidance
has been slowly shifting east and southeast with time, and the
area of potential Slight Risk continues to shrink. Believe this is
a lower end Slight Risk.

Southwest/Southern Rockies...
Enough moisture is available for scattered monsoon convection on
Sunday, with the most noted across south-central AZ. Hourly
amounts to 2" are possible due to diurnal heating, which would be
most problematic in urban areas, dry washes/arroyos, or burn scars.

New England/Northern Mid-Atlantic states...
A cold front is expected to sweep through the region, which could
lead to locally heavy pockets of rainfall. Available moisture and
instability supports hourly rain amounts to 2" where cells can
manage to train or merge. Both the 00z HREF and 18z RRFS have a
heavy rain signal from 12z onward this morning from the eastern tip
of Long Island near Block Island, Martha's Vineyard, and Nantucket.
Recent radar imagery (as of this writing) shows a vorticity maximum
in this general neighborhood which could be the responsible party.
If so, it appears to be running ahead of the model guidance and
shouldn't be the threat advertised. Radar estimates are quite low
in its vicinity as is.

Roth


Day 2
Valid 12Z Mon Jul 21 2025 - 12Z Tue Jul 22 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
KENTUCKY, TENNESSEE, SOUTHWEST WEST VIRGINIA, & WESTERNMOST VIRGINIA...

In and near KY & TN...
An axis of moisture and instability pivots between a convective
frontal wave offshore the Southeast and a strengthening warm
advection pattern across the Plains. Declining low-level inflow
is noted with time, but the GFS forecasts enough effective bulk
shear for some level of convective organization during the period
of daytime heating, which doesn't drop off significantly until
around sunset. Consideration the degree of saturation area soils
have now and the expectation for further saturation on Sunday and
Sunday night, adding a Slight Risk area here makes sense. Hourly
amounts to 3" with local totals to 5" are possible where cells
train or merge which would be most problematic in urban areas and
over saturated soils. This appears more likely within the defined
Slight Risk than the surrounding Marginal Risk area. There was
some consideration for a Slight Risk for coastal sections of NC,
but with coastal marsh in some of those areas, decided against it.

Plains/Southern Rockies...
Surface boundaries/low pressure areas/upper level disturbances are
on this move this period, which along with warming temperatures at
700 hPa/increased mid- level capping across portions of the
Central Plains and IA should limit QPF and flash flood potential
elsewhere. Hourly amounts up to 2" and local totals to 4" are
considered possible in this region. At the moment, it appears any
flash flooding would be on an isolated to widely scattered basis.
In the Southwest and Southern Rockies, burn scars and dry
washes/arroyos would be most at risk. Anywhere within these
regions, urban areas would be of most concern.

Roth


Day 3
Valid 12Z Tue Jul 22 2025 - 12Z Wed Jul 23 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
MINNESOTA, NORTHERN WISCONSIN, & NORTHWESTERN MICHIGAN...

In and near the Western Great Lakes...
A strengthening low-level jet out of the southwest is expected
downwind of an amplified Western trough and under the base of a
cold low moving across central Canada. Precipitable water values
rise to 2"+ and a broad reservoir of CAPE up to 5000 J/kg builds
near southeast SD due to significant warming at 700 hPa/a
strengthening mid-level capping inversion across portions of the
Plains to the east of the Western trough. Effective bulk shear
should be more than sufficient for organized thunderstorms,
including mesocyclone formation. Weekly rainfall anomalies show
that portions of the Arrowhead Peninsula and Upper Peninsula of
MI have had 300%+ of their average rainfall, leading to some degree
of saturation. Hourly rain amounts to 2.5" with local amounts to
5" could lead to flash flooding, with urban areas most prone to
issues. The Slight Risk was shifted somewhat north of continuity
per the latest guidance.

Southeast...
A potentially convective low retrogrades through portions of
northern FL this period. Precipitable water values rise to 2-2.25".
CAPE should rise to 3000 J/kg due to either daytime heating where
present or due to onshore flow from the warm western Atlantic,
Gulf, and FL Straits. There does appear to be enough effective bulk
shear present for at least some loose convective organization.
Hourly amounts to 3" and local totals to 6" are possible here.
Considered a Slight Risk as some portions of northern FL saw above
average precipitation with the previous retrograding convective low
on July 16-17, but the heavy rain signal at the moment shows
minimal overlap with the the previous convective low's rainfall footprint.

Southern Rockies...
Enough moisture and instability is expected to hourly amounts up
to 2" and local totals to 4", with a distinct diurnal cycle
expected. At the moment, it appears any flash flooding would be on
an isolated to widely scattered basis. Burn scars and dry
washes/arroyos, and urban areas would be most at risk.

Roth
$$
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FOUS30 KWBC 250853 AAA
QPFERD

Excessive Rainfall Discussion...UPDATED
NWS Weather Prediction Center College Park MD
453 AM EDT Fri Jul 25 2025

Day 1
Valid 12Z Fri Jul 25 2025 - 12Z Sat Jul 26 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE CENTRAL PLAINS, MIDWEST, AND OHIO VALLEY...

...Central Plains to southern Great Lakes...

Deep moisture and a front extending from the Plains to New England
is the main focus for potentially excessive rainfall today and tonight...especially across the plains where surface low pressure
helps focus convection along the front. However...plenty of
uncertainty lingers with the evolution/progression of the low...any
MCV or outflow boundary that could disrupt placement/magnitude of
any forcing in the low levels...and a mid- and upper- level
disturbance hugging the Gulf coast. Despite that uncertainty...and
in deference to the convective evolution Thursday night/early
Friday morning prior to the start of the Day 1 period combined with
the amounts still expected to fall being in largely the same
geographic placement...warrantied a the upgrade to a Moderate risk
in the Plains. Local 1.5 to 3 inch per hour rainfall rates and 2
to 4 inch rainfall totals along with isolated higher maximum
amounts remain in the realm of possibilities. A Slight risk area
extended into portions of the Ohio Valley along the best moisture
transport vectors.

Downstream from there...across portions of the Great Lakes into New England...maintained a Marginal Risk area along a corridor of 2
inch precipitable water values which should be aligned along and
ahead of the cold front. The front should continue to provide a
focus for showers and thunderstorms. Even though it is an
environment which supports isolated convection capable of
producing torrential downpours...the coverage of storms should be
much less than areas upstream and the progressive nature of
individual storms should be enough to mitigate concerns over a
widespread area.

...Northern Plains...

A quick moving shortwave ejecting out of the Rockies will sweep
across the Northern Plains later tonight/early Saturday morning
with scattered thunderstorms likely to roll through the Dakotas
after sunset. With precipitable water values climbing upwards of
+2 deviations along with ample mid-level forcing...a period of
enhanced heavy rainfall prospects during the time frame of impact. Deterministic output remains chaotic in terms of placement and
generally low in magnitude...but 1-3" of rainfall in a short
period of time would be sufficient for at least low-end MRGL.

...Gulf Coast...

The disturbance across the northern Gulf will continue to slowly
propagate west- southwestward with an attendant surface low
remaining situated just south of the west-central Gulf coast.
Current model guidance still keeps the feature far enough offshore
to preclude widespread impacts. However, the airmass surrounding
the disturbance will still be pretty robust with precipitable water
values remaining very high (>2.3") for much of the immediate
coastal plain over TX back through the central Gulf coast.

Bann


Day 2
Valid 12Z Sat Jul 26 2025 - 12Z Sun Jul 27 2025

...THERE ARE MARGINAL RISK AREAS FOR EXCESSIVE RAINFALL OVER
MULTIPLE REGIONS OF THE COUNTRY ON SATURDAY...

...Gulf Coast...

The upper trough and associated surface low hugging the Gulf coast will
remain situated across the western half of the Gulf with the main
area of surface reflection likely coming ashore into TX during the
period. Model solutions remain varied...but high precipitable
water and enough mid- and upper level forcing to continue producing
downpours across the central and western Gulf coast with an
emphasis on the immediate coastal plain.

...Northern Plains...

The next in a series of potent shortwave will eject northeast out
of the northern High Plains resulting in another round of heavy
precip potential with more organized convective clusters migrating
through the Dakotas. Isolated 2 to 3 inch rainfall maxima are
possible and embedded within broader areas of lesser rainfall
amounts. The pattern is fairly progressive so see little reason to
move from the Marginal risk category.

...Northeastern California and Northwest Nevada...

Almost a carbon copy of the prior period for convective impacts
lingering across the Northern Sierra up through northeastern CA and
northwest OR. The upper pattern is pretty slow to breakdown with
the diffluent area in the longwave setup still situated over
northern CA into NV. Instability is expected to be modest and
slightly above normal moisture in the terrain will offer the
capability for some isolated flash flood concerns within any
complex terrain and burn scar remnants in the above area.

Bann


Day 3
Valid 12Z Sun Jul 27 2025 - 12Z Mon Jul 28 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE UPPER MIDWEST...

...The eastern Dakotas to northern Minnesota... Effects of a
shortwave trough interacting with a surface front across the Upper
Midwest will continue into Sunday as does uncertainty with
placement and timing of any convection capable of supporting heavy
rainfall. There are some signals in the GFS and ECMWF for possible
MCS development while the NAM does generate some storms but would
be less concerning, Given the amount of rainfall recently across
parts of northern Minnesota...will maintain the Slight risk in
deference by the GFS/ECMWF for the time being.

...The Mid Atlantic to southern New England...
Mid-level flow flattens over the Great Lakes and Ohio
Valley...allowing embedded shortwave energy to start digging east
of there with corresponding height falls. The atmosphere will still
be anomalously moist and capable of supporting convection with
localized downpours that produce localized flooding.

...Southwest US...
Deeper moisture that made its way across parts of the Gulf and
inland across Mexico should start to be drawn northwest into parts
of the Southwest United States...resulting in scattered late day
and evening convection across parts of New Mexico and a small
portion of Arizona.

Bann
$$
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FOUS30 KWBC 260842
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
442 AM EDT Sat Jul 26 2025

Day 1
Valid 12Z Sat Jul 26 2025 - 12Z Sun Jul 27 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PARTS OF
THE SOUTHERN GREAT LAKES AND PENNSYLVANIA...

Heavy to excessive rainfall is possible along a corridor associated
with vort energy embedded within mid-level flow which was interacting
with a quasi- stationary front and a modestly unstable, but very
moist airmass pooled along it.The continuous influx of high PW
values over this boundary will aid in locally enhanced rainfall.
In addition...the winds aloft will be favorable for training and
backbuilding of storms over recently wet soils. This will elevate
the risk for localized flash flooding, especially for the flash
prone areas within the terrain of Pennsylvania and surrounding
locations. Given the amount of rain that fell in parts of Illinois
on Friday and in the overnight period from Friday night into early
this morning prior to the start of the Day 1 period...introduced a
Slight risk area in addition to the one that was already issued.

...Gulf Coast...

The disorganized area of showers and thunderstorms associated with
a trough of low pressure situated across the western half of the
Gulf will make its way inland over southeast Texas today. Deep
moisture/high precipitable water values and mid- and upper level
forcing continue producing downpours across the central and
western Gulf coast with an emphasis on the immediate coastal plain.

...Northern Plains...

The next in a series of potent shortwaves will eject eastward
across the noerhern tier of states of the Northern Plains...resulting
in another round of heavy precip potential with more organized
convective clusters migrating through the Dakotas. Isolated 2 to 3
inch rainfall maxima are possible and embedded within broader areas
of lesser rainfall amounts. The pattern is fairly progressive so
see little reason to move from the Marginal risk
category...although minor nudges were made based on the latest guidance.

...Northeastern California and Northwest Nevada...

Almost a carbon copy of the prior period for convective impacts
lingering across the Northern Sierra up through northeastern
California and northwest Oregon. The upper pattern is pretty slow
to breakdown with the diffluent area in the longwave setup still
situated over northern California into Nevada. Instability is
expected to be modest and slightly above normal moisture in the
terrain will offer the capability for some isolated flash flood
concerns within any complex terrain and burn scar remnants in the above area.

Bann


Day 2
Valid 12Z Sun Jul 27 2025 - 12Z Mon Jul 28 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE UPPER MIDWEST...

...The eastern Dakotas and Upper Midwest...

The effects of a shortwave trough interacting with a surface front
across the Upper Midwest will continue into Sunday as does
uncertainty with placement and timing of any convection capable of
supporting heavy rainfall. Convection early in the period looks to
be progressive enough to preclude much thereat of excessive
rainfall. However...there should be a weak boundary to the
southwest of the initial convection track with stronger
instability to the south. The instability and the shear set up a
scenario where additional convection will be more capable of
producing heavy to potentially excessive rainfall. Opted to
maintain a the previously issued Slight risk area after shifting
the area eastward.

...The Ohio Valley and Mid Atlantic to southern New England...
Mid-level flow flattens over the Great Lakes and Ohio
Valley...allowing embedded shortwave energy to start propagating
eastward. With the center of the upper high expected to shift just
far enough eastward...some weak height falls will allow shortwave
energy to dig over parts of the Mid-Atlantic. With an anomalously
moist air mass in place...convection with localized downpours have
a low-end threat to result in localized flooding.

...Southwest US...
Deeper moisture that made its way across parts of the Gulf and
inland across Mexico should start to be drawn northwest into parts
of the Southwest United States...resulting in scattered late day
and evening convection across parts of New Mexico and a small
portion of Arizona.

Bann


Day 3
Valid 12Z Mon Jul 28 2025 - 12Z Tue Jul 29 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE NORTHERN
HIGH PLAINS INTO THE UPPER MIDWEST AND ACROSS PARTS OF THE
SOUTHWEST UNITED STATES...

...Plains of Eastern Montana to parts of the Upper Midwest...
Showers and thunderstorms capable of producing excessive rainfall
are possible on Monday and Monday night from the plains of Montana southeastward into parts of the Upper Midwest as surface/low level
flow accelerates between low pressure to the south and high
pressure strengthening over southern Canada. Development of surface
low pressure over southwest South Dakota/northwest Nebraska
results in moisture transport up and over the boundary...leading to
a better chance for enhanced rainfall rates from the Dakotas into
Minnesota or Iowa. Farther west...there should be a feed of
moisture and some instability in the easterly flow into eastern
Montana. Given considerable uncertainty...not incline for more than
a Marginal risk area.

...Southwest US...
A continuation of deeper moisture transport into the Southwest US
will linger into Monday...with a continued chance for scattered
late day and evening convection across parts of New Mexico and a
small portion of Arizona that extends northward along the southern
and central Colorado front range.

Bann
$$
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FOUS30 KWBC 261554
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1154 AM EDT Sat Jul 26 2025

Day 1
Valid 16Z Sat Jul 26 2025 - 12Z Sun Jul 27 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PARTS OF
THE SOUTHERN GREAT LAKES AND PENNSYLVANIA...

16Z... In coordination with the New offices an upgrade to a Slight
Risk was made for the rest of the period. The PW values will be
near a daily max and certainly could fuel locally enhanced rain
rates leading to isolated flash flooding, especially over
sensitive terrain. The Slight spans across central/eastern New
York. The Slight over much of Pennsylvania was broadened a little
in a NW to SE fashion. The latest guidance depicts higher rainfall
rates for far northeast Ohio/northwest Pennsylvania than previous
forecast and for western portions of Ohio.

Campbell

Heavy to excessive rainfall is possible along a corridor associated
with vort energy embedded within mid-level flow which was interacting
with a quasi- stationary front and a modestly unstable, but very
moist airmass pooled along it.The continuous influx of high PW
values over this boundary will aid in locally enhanced rainfall.
In addition...the winds aloft will be favorable for training and
backbuilding of storms over recently wet soils. This will elevate
the risk for localized flash flooding, especially for the flash
prone areas within the terrain of Pennsylvania and surrounding
locations. Given the amount of rain that fell in parts of Illinois
on Friday and in the overnight period from Friday night into early
this morning prior to the start of the Day 1 period...introduced a
Slight risk area in addition to the one that was already issued.

...Gulf Coast...

The disorganized area of showers and thunderstorms associated with
a trough of low pressure situated across the western half of the
Gulf will make its way inland over southeast Texas today. Deep
moisture/high precipitable water values and mid- and upper level
forcing continue producing downpours across the central and
western Gulf coast with an emphasis on the immediate coastal plain.

...Northern Plains...

16Z update... Current observations show organized convection
tracking across Minnesota with a renewal of thunderstorm
development this afternoon and evening for the Dakotas and
Minnesota. Guidance is depicting the line of storms to progress
further east which is outside of the morning issuance of the
Marginal Risk. The eastern boundary was adjusted eastward to
account for this trend.

Campbell

The next in a series of potent shortwaves will eject eastward
across the northern tier of states of the Northern
Plains...resulting in another round of heavy precip potential with
more organized convective clusters migrating through the Dakotas.
Isolated 2 to 3 inch rainfall maxima are possible and embedded
within broader areas of lesser rainfall amounts. The pattern is
fairly progressive so see little reason to move from the Marginal
risk category...although minor nudges were made based on the latest
guidance.

...Northeastern California and Northwest Nevada...

Almost a carbon copy of the prior period for convective impacts
lingering across the Northern Sierra up through northeastern
California and northwest Oregon. The upper pattern is pretty slow
to breakdown with the diffluent area in the longwave setup still
situated over northern California into Nevada. Instability is
expected to be modest and slightly above normal moisture in the
terrain will offer the capability for some isolated flash flood
concerns within any complex terrain and burn scar remnants in the
above area.

Bann


Day 2
Valid 12Z Sun Jul 27 2025 - 12Z Mon Jul 28 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE UPPER MIDWEST...

...The eastern Dakotas and Upper Midwest...

The effects of a shortwave trough interacting with a surface front
across the Upper Midwest will continue into Sunday as does
uncertainty with placement and timing of any convection capable of
supporting heavy rainfall. Convection early in the period looks to
be progressive enough to preclude much thereat of excessive
rainfall. However...there should be a weak boundary to the
southwest of the initial convection track with stronger
instability to the south. The instability and the shear set up a
scenario where additional convection will be more capable of
producing heavy to potentially excessive rainfall. Opted to
maintain a the previously issued Slight risk area after shifting
the area eastward.

...The Ohio Valley and Mid Atlantic to southern New England...
Mid-level flow flattens over the Great Lakes and Ohio
Valley...allowing embedded shortwave energy to start propagating
eastward. With the center of the upper high expected to shift just
far enough eastward...some weak height falls will allow shortwave
energy to dig over parts of the Mid-Atlantic. With an anomalously
moist air mass in place...convection with localized downpours have
a low-end threat to result in localized flooding.

...Southwest US...
Deeper moisture that made its way across parts of the Gulf and
inland across Mexico should start to be drawn northwest into parts
of the Southwest United States...resulting in scattered late day
and evening convection across parts of New Mexico and a small
portion of Arizona.

Bann


Day 3
Valid 12Z Mon Jul 28 2025 - 12Z Tue Jul 29 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE NORTHERN
HIGH PLAINS INTO THE UPPER MIDWEST AND ACROSS PARTS OF THE
SOUTHWEST UNITED STATES...

...Plains of Eastern Montana to parts of the Upper Midwest...
Showers and thunderstorms capable of producing excessive rainfall
are possible on Monday and Monday night from the plains of Montana southeastward into parts of the Upper Midwest as surface/low level
flow accelerates between low pressure to the south and high
pressure strengthening over southern Canada. Development of surface
low pressure over southwest South Dakota/northwest Nebraska
results in moisture transport up and over the boundary...leading to
a better chance for enhanced rainfall rates from the Dakotas into
Minnesota or Iowa. Farther west...there should be a feed of
moisture and some instability in the easterly flow into eastern
Montana. Given considerable uncertainty...not incline for more than
a Marginal risk area.

...Southwest US...
A continuation of deeper moisture transport into the Southwest US
will linger into Monday...with a continued chance for scattered
late day and evening convection across parts of New Mexico and a
small portion of Arizona that extends northward along the southern
and central Colorado front range.

Bann
$$
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FOUS30 KWBC 270901
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
501 AM EDT Sun Jul 27 2025

Day 1
Valid 12Z Sun Jul 27 2025 - 12Z Mon Jul 28 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE UPPER MIDWEST, NORTHERN APPALACHIANS AND PARTS OF THE NORTHEAST...

...The eastern Dakotas and Upper Midwest...
Continue to make minor adjustments to the placement of a Slight
Risk area mainly confined to Minnesota as a shortwave trough
continues to propagate eastward along the northern tier of states.
There has been an upward trend in the guidance...both in the
coarser/global guidance and with the CAMs and related ensemble
forecast systems. With guidance now showing 2000 to 3000 J per kg
being possible and precipitable water values approaching 1.5
inches,,,another expansion southward of the Slight and Marginal
risk areas was made compared with the previous outlook.

The Marginal Risk area on the northern/western periphery of the
Slight risk area was expanded into North Dakota as a well developed
line of convection was moving across the state and not likely to
diminish prior to the start of the Day 1 period at 12Z.

...The Ohio Valley and Mid Atlantic to southern New England...

The Slight Risks which were raised over the Ohio Valley was
expanded to the west as a complex from overnight moves eastward.
The expectation is that the convection should weaken for a period
before reigniting later. Made a few changes to the outlook area
from the DelMarVa northward based on latest guidance. Locally
enhanced rainfall will persist in the very moist environment near
the west- east frontal boundary.

...Southwest US...

Deeper moisture that made its way across parts of the Gulf and
inland across Mexico should start to be drawn northwest into parts
of the Southwest United States...resulting in scattered late day
and evening convection across parts of New Mexico and a small
portion of Arizona.

Bann


Day 2
Valid 12Z Mon Jul 28 2025 - 12Z Tue Jul 29 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE NORTHERN PLAINS...

...Plains of Eastern Montana to parts of the Upper Midwest...
A surface cold front and mid-level shortwave trough will be
approaching an area rich in moisture and instability over parts of
South Dakota and Minnesota/Iowa on Monday afternoon. With low
level flow likely to increase the amount of moisture transport into
the region during the evening with a corresponding increase in
moisture flux convergence along the front...the potential exists
for excessive rainfall especially in the event of cell training or
repeat convection. Uncertainty remained with respect to placement
in the numerical guidance...but the RRFS seemed too far north. The
WPC deterministic QPF was closer to a GEFS/ECMWF ensemble mean
position...which still left some room for excessive rainfall to
build south. Consequently...allowed for a somewhat broader apron of
Slight Risk than shown by guidance.

Surrounding the Slight risk area...only modest changes were made
to the Marginal risk area extending northwest into the plains of
eastern Montana where a secondary QPF maximum is expected. The
expectation is that there will be two discrete QPF area with a risk
of excessive rainfall associated with each...but maintained the
one area given the range of possible solutions.

...Southwest US...

A continuation of flow with deeper moisture into the Southwest US
will linger on Monday and Monday night...with a continued chance
for scattered late day and evening convection across parts of New
Mexico and a small portion of Arizona that extends northward along
the southern and central Colorado front range.

Bann


Day 3
Valid 12Z Tue Jul 29 2025 - 12Z Wed Jul 30 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE WESTERN HIGH PLAINS...

Northern Rockies eastward to Great Lakes and southward to the Southwest US...

Building mid-level ridge over British Columbia and Albert will
result in lowering heights over parts of the northwestern US and
increasing mid- and upper flow. This results in an increasingly
well defined surface boundary that serves to focus showers and
thunderstorm on Tuesday. Ingredients for thunderstorms to produce
heavy to potentially excessive rainfall appear to be aligning from
southeast Montana into northern Nebraska along a corridor of 1000
to 2000 J per kg instability and 1 to 1.25 inch precipitable
water values...and even some 1.5 inch PW values in northern
Nebraska. Showers and thunderstorms are also likely to spread
eastward toward the Great Lakes where the instability and synoptic
scale forcing looks to be weaker. In addition...another round of
late day convection is possible from the Southwest US into the
Rockies and some of this moisture may approach...if not come into
play,,,across the western High Plains late in the period.

...Southeast US...
Precipitable water values in excess of 2 inches will be in place
with 1000-1500 J per kg of CAPE in place and weakening of the broad
upper level ridge should lead to a somewhat better chance for
showers or thunderstorms on Tuesday. The GFS and ECMWF both show
hints at weak vorticity centers in the vicinity to help
focus/support some activity. The expectation is that isolated but
very intense rainfall rates could lead to isolated instances of
excessive rainfall.

Bann
$$
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FOUS30 KWBC 280813
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
413 AM EDT Mon Jul 28 2025

Day 1
Valid 12Z Mon Jul 28 2025 - 12Z Tue Jul 29 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY..

...Northern Plains to Upper MS Valley...
Convection will move across portions of eastern MT and into the
western Dakotas this morning. Heavy rainfall rates with this
activity will pose a localized flash flood risk, however generally
quick cell motions should limit the extent of the threat. As we
head into the afternoon and evening hours this convection will
grow upscale into an MCS as it moves across central SD into
southern MN and northern IA. A forward propagating derecho is
likely given the environmental ingredients in place and per SPC.
This fast forward motion will likely cap the extent of any flash
flood risk at the Slight level.

The impressive CAPE and PWs around 2" near and just downstream of
the MCS will support heavy rainfall rates. As the MCS matures the
heaviest rainfall totals may end up near the developing comma
head/bookend vortex where rainfall duration will be locally longer.
The 00z HREF supports total rainfall over 2", with a narrow axis
of over 3" probable as well. Portions of eastern SD into southwest
MN received heavy rainfall this past night...and so if an
additional 2-3" falls over these areas then isolated to scattered
flash flooding is likely. Elsewhere, the threat is likely an urban
risk driven by hourly rainfall locally as high as 2" as the MCS
moves through.

...Southwest..
Another day of scattered afternoon convection expected across much
of NM into far southeast AZ. Both PWs and CAPE are forecast to be
higher today compared to yesterday, and so do anticipate a bit
more convective coverage today. Activity will initially develop
near areas of terrain, such as the Sacramento Mountains and Sangre
De Cristos. Given the moisture and instability in place...at least
an isolated flash flood threat is likely on/near these higher
terrain areas, especially over the more sensitive burn scars. Cells
may tend to be transient today...either moving off to the west
and/or dissipating fairly quickly, which may keep the flash flood
coverage isolated in nature. Convection could actually persist into
the overnight hours over portions of southern NM...but the extent
of instability by this time is unclear, and so rainfall rates
should be tempered by this time. Overall this is a solid Marginal
risk with isolated flash flooding likely, but at the moment think
the risk falls just shy of Slight risk level coverage.

...OH Valley into the Carolinas...
Isolated to scattered thunderstorms are expected today across a
broad area stretching from KY/TN to southern MI and all the way to
the coastal Carolinas. Generally not expecting much organization
to convection...but PWs of around 2" (or higher) will continue to
support heavy rainfall rates. Localized rainfall of 2-3" are
possible within the Marginal risk area...and while the coverage of
these amounts should be small...where it does fall some flash
flood impacts are possible within areas of lowered FFG. The most
concentrated probabilities in the HREF are actually over the
coastal Carolinas, where a convergence axis should drive more
convective coverage and some totals locally over 3". However with
higher FFG over these areas the flash flood risk is still expected
to stay isolated.

Chenard


Day 2
Valid 12Z Tue Jul 29 2025 - 12Z Wed Jul 30 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE CENTRAL AND NORTHERN PLAINS...

...Central and Northern Plains...
A stationary front will likely extend across southern IA/NE and
into the High Plains on Tuesday afternoon/evening. Easterly flow to
the north of this front will likely help trigger convective
development over the High Plains as shortwave energy moves out of
the Rockies and upper level divergence increases in the right
entrance region of an upper jet. This activity will likely push
east into the overnight hours across NE and eventually IA
along/north of the stationary front. Upscale development into an
MCS appears probable driving a heavy rainfall threat. Any eventual
MCS will probably propagate off to the east fairly quickly, however
additional development downstream over NE/IA is possible given the
convergence near the front and what should be CAPE around 4000
j/kg. PWs should be plenty high enough for heavy rainfall, ranging
from 1.5" in the High Plains to locally over 2" from eastern NE into IA.

There remains some latitudinal uncertainty with the axis of
convection during this period...although the general trend has
been for a slightly farther south axis. There is also some question
as to how far east the risk exists, with the deterministic and
ensemble EC and the 00z RRFS/REFS favoring NE, but the GFS and
AIFS extending the threat into IA. Given a favorable track record
for the AIFS and the presence of the boundary/instability/PWs over
IA, we did want to make sure that the Slight risk at least covered
into central IA.

...Southwest...
Another day of scattered afternoon convection expected Tuesday.
Probabilities from both the 00z HREF and REFS show a bit more
persistence of high 1"/hr exceedance over the Sacramento Mountains
and vicinity. Thus the flash flood risk over these areas, and the
susceptible burn scars, may very well be higher Tuesday than
Monday. However there are some questions regarding the coverage of
heavier rainfall amounts away from these terrain areas, as the
overall coverage could be a bit less than Monday. Given the small
extent of the higher risk at the moment and the uncertainty on the
broader coverage, we will leave the ERO at a Marginal level
pending what happens Monday. Although locally significant impacts
are possible within/near the Sacramento Mountain burn scars.

...Southeast...
Expecting greater convective coverage on Tuesday from the Southeast
into the southern Appalachians. Not much in the way of forcing to
organize convection, and generally expecting pulse activity that
does not last all that long at any one location. This will act as
a limiting factor for flash flooding...however there should be
enough convective coverage that some cell mergers along outflows
will be a possibility. PWs in the region are forecast between 2"
and 2.3", with CAPE over 2000 j/kg...so the thermodynamic
environment will support heavy rainfall rates. Thus even with a
relatively short duration of rain at any one location, rainfall
totals locally over 3" appear probable driving a localized flash flood risk.

Chenard


Day 3
Valid 12Z Wed Jul 30 2025 - 12Z Thu Jul 31 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE MIDDLE MISSISSIPPI VALLEY...

...Mid MS Valley...
At 12z Wednesday it seems likely that we will have some degree of
organized convection ongoing in the vicinity of IA, although at
this lead time getting these specifics right is tricky.
Nonetheless, it appears probable that a better defined
shortwave/MCV will be associated with this convection and slowly
move east across IA/MO/IL and vicinity Wednesday into Wednesday
night. Meanwhile we will have a slowly southward shifting cold
front helping focus convergence, and the right entrance region of
the upper jet adding some divergence aloft. With plentiful CAPE
near the front and PWs locally over 2", the ingredients for areas
of excessive rainfall are in place. Some uncertainty remains on the details...but 00z models are coming into a better consensus on the
favored axis for heavy rainfall..generally stretching across
portions of IA, northern MO and into central/northern IL and
possibly portions of IN.

...Southwest and High Plains...
Isolated to scattered convection will likely develop near areas of
terrain from NM into the Rockies. Generally not looking like the
greatest forcing, so the degree of convective organization remains
unclear. At the moment most models indicate mostly
isolated/scattered development, and generally not enough coverage
for anything more than a Marginal risk. However there is some
potential for a few organized clusters to move off the terrain
into the High Plains, and so can not rule a targeted Slight risk or
two as we get closer in time and have more high res guidance to interrogate.

...Elsewhere...
A broad Marginal risk extends from the central Gulf Coast all the
way into portions of New England. High PWs and CAPE and convective
coverage will drive the risk from the Gulf Coast into the TN
valley. A lack of organization may keep FFG exceedance coverage
down, but high rainfall rates will likely locally approach or
exceed FFG. A cold front will drive the risk form portions of the
OH valley into New England. Generally quick cell motions and the
lack of a significant QPF footprint in the 00z models keep this
risk at a Marginal level.

Chenard
$$
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FOUS30 KWBC 300845
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
445 AM EDT Wed Jul 30 2025

Day 1
Valid 12Z Wed Jul 30 2025 - 12Z Thu Jul 31 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE MIDDLE MISSISSIPPI VALLEY AND FOR PORTIONS OF THE FRONT RANGE
AND ADJACENT HIGH PLAINS...

...Mid MS Valley...
An eastward moving squall line will be ongoing at 12z this morning
across portions of eastern IA into northern MO,and given the
downstream instability axis do expect this to generally survive
across much of central and northern IL into early this
afternoon. The progressive nature of this convection should limit
the extent and magnitude of flash flooding, however hourly rainfall
of 1-2" will remain likely. This will be enough to drive at least
an isolated flash flood risk as convection moves eastward. This
MCS/MCV will help drive a cold front south across MO and KS, and do
expect convection to expand over these areas by afternoon. A bit
unclear whether it takes the form of a progressive squall line
(limiting the flash flood risk), or if more discrete cell formation
allows for some training/cell merging.

The overall environment...a slowly southward shifting cold front
helping focus convergence, the right entrance region of the upper
jet adding some divergence aloft, plentiful CAPE near the front and
PWs locally over 2"...certainly supports areas of excessive
rainfall. At a minimum, isolated instances of flash flooding can
be expected across portions of KS/MO/IA/IL/IN. The magnitude and
coverage of this threat will come down to convective mode and
evolution today/tonight. As mentioned above, convective mode
generally favoring more progressive squall lines may end up
keeping the risk isolated. However if we are able to get any
recovery after this initial round of convection the MCV and
favorable synoptic and moisture ingredients will remain in place.
Thus, higher end impacts are still possible in this setup, but far
from guaranteed given the questions that remain regarding
convective mode/evolution and instability persistence.

...Southwest and High Plains...
Isolated to scattered convection will likely develop near areas of
terrain from NM into the Rockies. Easterly low level flow into the
Front Range of CO will likely result in slow cell motions and the
possibility of at least isolated flash flooding. Increased
convergence near the front could support a bit more convective
coverage and eventual organization from portions of eastern NM into the
OK and TX Panhandles as well. Only change to the inherited Slight
risk was to expand it northward into WY where both the HREF and
REFS show an uptick in 1" per hour probabilities by this evening as
convective coverage increases and a few cell mergers become likely.

...Elsewhere...
A broad Marginal risk extends from the central Gulf Coast all the
way into portions of southern NY. High PWs and CAPE and convective
coverage will drive the risk from the Gulf Coast into the TN
valley. A lack of organization may keep FFG exceedance coverage
down, but high rainfall rates will likely locally approach or
exceed FFG. A cold front will drive the risk form portions of WV
into southern NY. Convective coverage and organization should be lacking...however with the front slowing cells should be slow
moving and could drop a quick 1-2" of rain. Likely enough to drive
at least a localized urban flash flood risk.

Chenard


Day 2
Valid 12Z Thu Jul 31 2025 - 12Z Fri Aug 01 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE MID-ATLANTIC INTO SOUTHERN NEW ENGLAND...

...Mid-Atlantic into New England...
Heavy rainfall and at least some flash flooding appears likely
Thursday across portions of the Mid-atlantic and possibly into
southern New England. Convection is likely to focus along a slow
moving cold front, with broad mid level troughing and height falls
providing large scale ascent. The upper level jet is displaced
pretty far north, however still likely to get some enhanced upper
level divergence into the Mid-Atlantic from this feature.

Still quite a bit of uncertainty with the details of this
convective risk. Some of this uncertainty is tied to the evolution
of the shortwave/MCV associated with the ongoing convection over
IA/IL this morning. The strength of that feature and how it
interacts with the front and developing longwave troughing will
likely impact the frontal timing and both the axis and magnitude
of the flash flood risk. The front should become more progressive
by Thursday evening, but how things evolve before then are
unclear. There is a concern that we could see cell development
Thursday afternoon just ahead of the front as southerly flow
increases which could set the stage for a fair amount of cell
merger activity driving up rainfall totals. Also it looks like an
area of low pressure tries to spin up along the front Thursday
night with an inverted trough axis extending northward. The ECMWF
and 3km NAM keep this troughing inland, which could be a pretty
ideal setup for low topped warm rain convection through the
overnight. However, most other models push this troughing offshore
and clear things out by the overnight.

The environment (slow moving front, increasing large scale
forcing, PWs over 2" and plentiful instability) supports excessive rainfall...its just going to come down to location and duration,
both of which remain uncertain. The current consensus among the
models still supports a corridor from DC to PHL to NYC (including
much of eastern PA and NJ) as the areas most likely to be
impacted. The 00z experimental REFS ensemble neighborhood
probabilities of exceeding 5" are 40-70% across this corridor. The
REFS can run high with its QPF output, and may be under
dispersive...but nonetheless still a signal worth watching. We gave
some consideration to a MDT risk upgrade this cycle, but after
collaboration with local WFOs we opted to maintain a Slight risk
given some of the lingering questions on how the details of the
event will evolve. As the event comes more into range of the HREF
today and tonight we will hopefully gain more confidence on these
details, and a MDT risk upgrade is still a possibility with later
updates. For now this is still considered a higher end Slight risk
from DC to eastern PA, NJ and NYC, and locally significant impacts
could evolve.

...Gulf Coast into OH Valley...
Another day of slow moving pulse thunderstorms is expected over a
large swath of the region to the south of the cold front. Similar
to Wednesday, high PWs and CAPE and convective coverage will drive
a localized flash flood risk. A lack of organization may keep FFG
exceedance coverage down, but high rainfall rates will likely
locally approach or exceed FFG.

...Rockies into the Plains...
Scattered convection is likely from eastern AZ into NM northward
all the way into MT. Currently not seeing a strong indication of
organization that would lead to Slight risk level flash flood
coverage. However localized flash flooding will again be possible
over this broad region. There are some height falls beginning to
approach from the west, so that could perhaps end up driving a
more organized risk somewhere within this broad Marginal risk. But
at the moment not seeing enough of a signal in the global models
or CAMs to go with any Slight risk areas.

Chenard


Day 3
Valid 12Z Fri Aug 01 2025 - 12Z Sat Aug 02 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE CAROLINAS...

...Southeast and Mid-Atlantic...
A Slight risk was maintained across much of the carolinas. Likely
to have a well defined cold front dropping south over NC that will
help trigger a more organized corridor of convection Friday
afternoon. Meanwhile both terrain driven and coastal convergence
driven convection are also likely by afternoon. This combination
will result in good convective coverage, which will ultimately
likely lead to a decent degree of cell merger activity. PWs are
forecast as high as 2.3"-2.5", with plentiful instability. Very
heavy rainfall rates are expected in this thermodynamic
environment, which combined with the likelihood of cell mergers,
should drive an isolated to scattered flash flood risk.

There is still some degree of uncertainty with the details by
Friday. The 00z ECMWF is an outlier really hanging the front and
better upper level support well to the north. Thus it keeps a heavy
rainfall risk over NJ into NYC and less of a concentrated risk over
the Carolinas. This is not supported by the GFS/UKMET/CMC...and
the 00z ECMWF AIFS ensemble also looks more in line with the
GFS/GEFS. Thus we will continue to lean the EROs to be more in line
with the non ECMWF solution. However we will need to continue to
monitor trends going forward.

...Lower MS Valley and Vicinity...
A cold front should make it all the way into portions of TX/LA and
MS by Friday afternoon. This should act as a focus for convective
development, and with a large pool of PWs over 2", heavy rainfall
rates are likely. Large scale forcing and moisture transport is
weaker here, so not expecting widespread heavy rainfall...but
localized heavy rainfall rates should be able to drive an isolated
flash flood risk.

...Rockies and Plains...
Convection is likely from NM into MT Friday. The best environment
for heavy rainfall will probably be across the northern end of
this risk area, centered across MT and vicinity. More in the way
of mid level troughing will be over this corridor, to go along
with the highest PW anomalies in the CONUS...near early August
peak values. Combine this with CAPE forecast around 2000 j/kg and
the environment appears conducive to areas of flash flooding.
However none of the 00z global models are all that aggressive with
QPF output, and the one CAM that goes this far (the 00z RRFS)
suggests a more progressive convective mode. Thus we will stick
with a Marginal risk and continue to monitor trends.

Chenard
$$
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FOUS30 KWBC 311343
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
943 AM EDT Thu Jul 31 2025

Day 1 Valid 1328Z Thu Jul 31 2025 - 12Z Fri Aug 01 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE NORTHERN MID-ATLANTIC...

...Mid-Atlantic into New England...

14Z special update...

Adjusted the Moderate Risk this morning to include New York City
and parts of southern CT given the location of the frontal boundary
this morning and CAM trends. 12z HRRR depicts a reasonable scenario
with a line of slow-moving convection near New York City and along
coastal CT where an area of low-level convergence could anchor
storms along this region. Where storms do set up, rainfall rates
exceeding 2"/hr is likely to overwhelm the urbanized terrain along
I-95. An additional adjustment was made to expand the SLGT Risk
southward across the Blue Ridge of central VA. More information
will be available with the regular 16Z update.

Snell

A potent vorticity max paralleled with an exceptionally strong
upper level jet streak over southeast Canada and highly anomalous
moisture content will spin up a surface low along a frontal
boundary over the northern Mid- Atlantic and spread enhanced
rainfall to a vast portion of the East. There are two areas of
concern regarding heavy rainfall. The first area is from northeast
Pennsylvania on east through the Lower Hudson Valley and into
southern New England will have a band of heavy and efficient
rainfall. PWATs will rise to the 1.8-2.0" range and low-level WAA
ahead of the front will give rise to potential training. There is
uncertainty regarding the amount of available instability, which
could reach as high as 500 J/kg. Still, the modeled soundings
depict warm cloud layers up to 13,000ft deep, so while rates may
not be as high as farther to the south, warm rain processes could
still provide 1-1.5"/hr rates in these areas Thursday afternoon and
into Thursday night. A Slight Risk remains is in place for these
regions with locally significant flash flooding possible,
particularly for areas closer to the Poconos, higher elevations of
southern New England.

Northern Mid-Atlantic: Farther south, while the Mid-Atlantic
region is a little farther removed from the jet-streak dynamics to
the north, the region is closer to the deepening surface low with
strong surface-925mb southerly theta-e advection directed into the
surface front. From northern NJ and southern PA on south to
northern VA, a tropical air-mass (depicted by 2-2.25" PWATs and
low-mid 70s dew points) will coincide within a warm sector that
becomes increasingly unstable (MUCAPE between 1,000-2,000 J/kg). It is
worth noting that SST anomalies along the Mid-Atlantic and
Southeast coasts are well above normal too, acting as an abnormally
rich moisture source for southerly low-level flow to draw from. By
Thursday afternoon, low-level WAA into the front will support
storms enveloping the region with additional storms from the
Appalachians tracking east. Modest vertical wind shear aloft will
also support organized clusters of storms, some of which will have
the potential to backbuild and train over the I-95 corridor into
Thursday night. Latest 12Z HREF guidance shows 24-hr probabilities
for >3" of rainfall are high (>70%) from the DC/Baltimore area on
north through northeast MD, southeast PA, and into southern NJ.
Just as concerning is this same region sports 30-60% chances for

5" of rainfall.

Impact potential for Moderate Risk Area: These probabilities
listed above serve as signals in ensemble guidance that highlight
the potential for significant flash flooding throughout the country,
let alone over a highly populated urban corridor. Given the
atmospheric parameters in place, it is possible that the Mid-
Atlantic I-95 corridor witnesses thunderstorms that produce
rainfall rates up to 3"/hr, with perhaps the most intense storms
potentially generating 2" rainfall totals in as little as 30
minutes. QPF may seem light at first glance given the hourly
rainfall rate potential, but this is largely due to lingering
uncertainty in the placement of the heaviest rainfall. Many
individual convective models show localized totals surpassing 5"
with even some localized maxima approaching 8". Residents in the
Mid-Atlantic should ensure they have reliable means of receiving
warnings issued by their local WFOs throughout the day and into
Thursday night.

...Gulf Coast into Ohio Valley...

Slow moving thunderstorms will persist today and tonight over a
vast area south of the cold front. High PWs and CAPE and
convective coverage will drive a localized flash flood risk. A
lack of organization may keep FFG exceedance coverage down, but
high rainfall rates will likely locally approach or exceed FFG.
This region is covered by a Marginal Risk for excessive rainfall
and isolated flash flooding.

...Rockies into the Plains...

Scattered thunderstorms expected to fire up from eastern
Arizona/New Mexico northward to Montana. In general, the storms
will likely lack organization for a more elevated threat for flash
flooding. A Marginal Risk is the appropriate threat level at this time.

Mullinax/Campbell


Day 2 Valid 12Z Fri Aug 01 2025 - 12Z Sat Aug 02 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE CAROLINAS...

...Southeast and Mid-Atlantic...

During this period a cold front will be dropping south through the
region which will trigger a more organized corridor of convection
Friday afternoon. Meanwhile both terrain driven and coastal
convergence driven convection are also likely by afternoon. This
combination will result in good convective coverage, which will
ultimately likely lead to a decent degree of cell merger activity.
Much of the area will have PW values nearing 2.5 inches along with
abundant instability. PWs are forecast as high as 2.3"-2.5", with
plentiful instability. Very heavy rainfall rates are expected in
this thermodynamic environment, which combined with the likelihood
of cell mergers, should drive an isolated to scattered flash flood risk.

...Lower MS Valley and Vicinity...

Convection will fire along the cold front as is continues to drop
south during this period. Pooled PW values exceeding 2 inches will
aid in the development and enhancement of heavy rainfall across the
region. Large scale forcing and moisture transport is weaker here,
so not expecting widespread heavy rainfall...but localized heavy
rainfall rates should be able to drive an isolated flash flood risk.

...Rockies and Plains...

Scattered convection is expected to span from Montana to New Mexico
into Friday. The most favorable environment for heavy rainfall will
likely setup from Montana into the Dakotas, which is where mid
level troughing will be paired with the highest PW anomalies in
the CONUS...near early August peak values. Combine this with CAPE
forecast around 2000 j/kg and the environment appears conducive to
areas of localized flash flooding. Hourly rainfall rates up to
1.25-1.5 inches/hour possible over the Northern Rockies/Montana and
up to 2 inches/hour across the Dakotas.

Campbell/Chenard


Day 3 Valid 12Z Sat Aug 02 2025 - 12Z Sun Aug 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE SOUTHEAST...

...South and Southeast...

The strong front mentioned will continue pressing southward,
draped from the Southeast westward across the Deep South, Lower
Mississippi Valley and over Texas. High moisture content and
instability along and ahead of the front interacting with the right
entrance region of the upper jet will promote heavy to excessive
rainfall in thunderstorms that could cause localized flash
flooding. Very heavy rainfall rates are expected and should drive
an isolated to scattered flash flood risk. A Slight Risk remains in
effect for portions of South Carolina, southern Georgia and extreme
northeast Florida. The front stretching west across the Gulf Coast
states in a moist and unstable environment could promote scattered
diurnal thunderstorms into Saturday thus maintaining the Marginal Risk.

...Rockies and Plains...

Shortwaves rounding the eastern edge of the upper ridge in the
western U.S. is forecast to interact with the same front that bends
back across the Great Plains, where rounds of rain and
thunderstorms are likely with possibly multiple MCSs. High rain
rates should be supported at times with the above normal moisture
and instability with some areas possibly seeing repeated rounds of
storms as the front begins to lift as a warm front. The region is
covered by a Marginal Risk. Some lingering monsoonal moisture will
keep convection possible around southeastern New Mexico resulting
in isolated flooding concerns over sensitive burn scars.

Campbell
$$
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FOUS30 KWBC 010821
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
421 AM EDT Fri Aug 1 2025

Day 1
Valid 12Z Fri Aug 01 2025 - 12Z Sat Aug 02 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE CAROLINAS, NORTH/NORTHEAST TEXAS, NORTHEAST NEW MEXICO AND THE DAKOTAS...

...Southeast and Mid-Atlantic...

During this period a potent cold front will be dropping south
through the region in response to a very strong surface high
pressure (above the 99.5th climatological percentile per the NAEFS)
over the Great Lakes/Midwest. This will allow for moisture to pool
along the front and thunderstorms to develop across the Carolinas
on through Friday night. Meanwhile both terrain and coastal
influence are also likely, which may lead to slower storm motions
and heavier rainfall amounts. This combination will also result in
good convective coverage, which will ultimately likely lead to a
decent degree of cell merger activity. Much of the area will have
PW values nearing 2.5 inches along with abundant instability,
resulting in very heavy rainfall rates over 2"/hr in this
thermodynamic environment. Given the likelihood of cell mergers and
westerly mean layer flow nearly parallel to the front, this should
drive an isolated to scattered flash flood risk. 12z HREF guidance
depicted high neighborhood probabilities (60-90%) for at least 3"
in 6-hrs along the coastal Carolinas, where FFG is also highest.
Additionally, along the complex terrain of the western Carolinas
12z HREF neighborhood probabilities for exceeding 3" in 6-hrs are 40-50%.

Urban areas and the complex terrain of the southern Appalachians
remain most at risk to scattered instances of flash flooding, with
the remainder of the Carolinas flat and sandy soils capable of
soaking in most of the intense rainfall. The frontal boundary will
also linger across the remainder of the Southeast and into the
Lower MS Valley, where additional instances of flash flooding are
possible given weak steering flow and 2-2.25" PWs. However, most
storms should become outflow dominant and be short-lived after a
brief period of intense rainfall and rates up to 3"/hr.

...Southern Plains...

During this period a cold/stationary front will be draped across
the region within a pool of PW values near 2 inches. A surface
wave and meandering MCV could trigger locally heavy rain in
northern/northeast Texas Friday night. The exact location of
remains somewhat uncertain for the highest QPF however hi-res
guidance indicate 6-hr probabilities for >5" at 30-40%. A Slight
Risk was maintained with some expansion northward in northeast Texas.

...Rockies and Plains...

Scattered convection is expected to span from Montana to New Mexico
into Friday. The most favorable environment for heavy rainfall will
likely setup from Montana into the Dakotas, which is where mid
level troughing will be paired with the highest PW anomalies in
the CONUS...above the 90th percentile climatological early August
peak values. Combine this with CAPE forecast around 2000 J/kg and
the environment appears conducive to areas of localized flash flooding.

Hourly rainfall rates up to 1.25-1.5 inches/hour possible
over the Northern Rockies/Montana and up to 2-2.5 inches/hour
across the Dakotas. Although there still remains some uncertainty
on the exact location of an advancing MCV, guidance suggests
portions of south-central North Dakota and much of central South
Dakota will have an elevated threat for excessive rainfall and
isolated to scattered areas with flash flooding. A Slight Risk was
raised for this part of the Northern Plains.

Additionally, a Slight Risk was raised for northeast New Mexico
that covers parts of I-25/eastern Sangre de Cristo Mountains and
near I-40 and points to the north/northeast. Enhanced rainfall will
elevate the risk for runoff and flash flooding over the sensitive
terrain. Hourly rain rates may reach 1.5 inches/hour.

Campbell/Snell


Day 2
Valid 12Z Sat Aug 02 2025 - 12Z Sun Aug 03 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE SOUTHEAST AND THE CENTRAL/SOUTHERN PLAINS...

...South and Southeast...

During this period the strong cold front will sink southward
through the Southeast, Deep South and westward in to Texas. A deep
pool of moisture will remain readily available enhance local
rainfall, especially with the presence of instability along and
ahead of the front interacting with the right entrance region of
the upper jet. Very heavy rainfall rates are expected and should
drive an isolated to scattered flash flood risk. The Slight Risk
are was maintained for portions of the Low Country South Carolina,
southern Georgia and far northern/northeast Florida and was
expanded western into Alabama with this issuance. The front
stretching west across the Gulf Coast states in a moist and
unstable environment could promote scattered diurnal thunderstorms
into Saturday thus maintaining the Marginal Risk.

...Rockies and Plains...

Shortwaves rounding the eastern edge of the upper ridge in the
western U.S. is forecast to interact with the same front that bends
back across the Great Plains, where rounds of rain and
thunderstorms are likely with possibly multiple MCSs. High rain
rates should be supported at times with the above normal moisture
and instability with some areas possibly seeing repeated rounds of
storms as the front begins to lift as a warm front. While the the
location of the heaviest accumulations remain somewhat uncertain
the guidance is favoring locations in the vicinity of western
Kansas and Oklahoma. A Slight Risk was upgraded for this portion of
the plains.

Snell/Campbell


Day 3
Valid 12Z Sun Aug 03 2025 - 12Z Mon Aug 04 2025

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR SOUTHEAST
GEORGIA AND FOR THE CENTRAL/SOUTHERN PLAINS...

...Southeast...

Once again the cold front advances further south, shifting the QPF
footprint along with it. The heaviest rainfall will likely focus
along the far southern portions of South Carolin and coastal
Georgia, therefore kept the Slight Risk for this period. A broader
Marginal Risk area covers the potential for isolated instances of
excessive rainfall as far west as the Florida Panhandle and
southeast Alabama.

...Plains...

MCSs mentioned in the Day 2 period will persist during this period
although shifted east/south further into the plains. Deep influx of
PW near 2 inches will continue to fuel convection and enhance
rainfall rates within these complexes. The exact location of the
highest totals are not certain but the higher potential for
excessive rainfall and flash flooding concerns will likely be
focused over south-central Kansas and northern Oklahoma. The Slight
Risk area was maintained for this period.

Campbell
$$
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FOUS30 KWBC 030826
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
426 AM EDT Sun Aug 3 2025

Day 1
Valid 12Z Sun Aug 03 2025 - 12Z Mon Aug 04 2025

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTHEAST/GULF COAST AND SOUTHERN PLAINS...

...Southeast/Gulf Coast...

The cold front will continue to waver along the Gulf Coast as a
stationary front in response to subtle additional height falls as
the trough extending from the Northeast continues to subtly
amplify. The trough axis may reach the Gulf Coast by evening, but
flatten at the same time in response to an elongated ridge draped
across the Gulf. A constant pool of anomalous PW values (above
2.25 inches with deep column saturation) noted via moist-
adiabatic lapse rates through the depth of the column indicating
tall-skinny CAPE which is progged to reach above 1000 J/kg during
peak heating. Convergence along the front into these thermodynamics
will support another day of slow moving convection noted by 0-6km
mean winds of just 5-10 kts pointed to the east, with rainfall
rates likely exceeding 2 inches/hour at times (HREF 50-60% chance)
supported by warm cloud depths nearing 15,000 ft to produce
efficient warm- rain collision processes.

Shortwave energy is expected to rotate beneath the trough, tracking
from the Florida Panhandle into eastern Georgia. This features may
support an increase in areal coverage of convection and possibly
organizing into clusters/multi-cells. With weak storm motions in
place, any collisions/organization during this time could briefly
pulse up rain rates even more significantly, while also leading to
longer temporal duration or repeating rounds of these rain rates.
Where this occurs, the HREF and REFS both indicate a 70-90% chance
of 3 inches/24 hours and locally a 40-70% chance of more than 5
inches/24 hours. These accumulations are forecast to occur where
recent rains have been heavy and increased soil saturation. The
inherited Slight Risk was expanded west/northwest to cover more of central/eastern Alabama and western Georgia.

Otherwise, scattered thunderstorms with intense rain rates could
produce instances of flash flooding. Models are depicting a
secondary area of maximum rainfall potential along a westward
advancing surface trough through northern Alabama into central
Tennessee which may require an upgrade in the ERO with later
issuances since 3 inches/24hr probabilities peak at 40-50%, but
this correlated with 3-hr FFG exceedance that is just 10-15%.

...Plains...

The stationary front stretching from Montana to Texas is expected
to weaken, leaving behind a weak convergence boundary as it
decays. Mid-level flow upstream of this feature will gradually
become more W/NW as it gets squeezed between an amplifying ridge
over the Southwest and a trough across Canada. Within this pinched
flow, multiple shortwaves/vorticity impulses will shift eastward,
interacting with the front to cause another day of convective
development across the High Plains and into the Plains, with
several MCSs possible beneath any of the stronger impulses.

The exact location and track for any of the MCSs that develop
remain uncertain however there is a decent signal for storms to
have rainfall rates of 1-2 inches/hour. While the CAMs are
generally suggestive of forward propagating features that will
limit the duration of heavy rainfall, locally any of these could
produce some short-term training, especially where any MCVs and
lingering boundaries can track. There are hints that a narrow swath
of higher QPF will streak from the Dakotas to Minnesota but the
spread was too great to consider a Slight Risk upgrade at this but
may be considered for updates later today. The Slight Risk over
Texas and southwest Oklahoma was maintained as it highlights the
areas where there will be an elevated threat for flash flooding.

Campbell/Weiss


Day 2
Valid 12Z Mon Aug 04 2025 - 12Z Tue Aug 05 2025

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR THE SOUTHEAST...

...Southeast...

A surge in moisture ahead of the longwave trough axis will
maintain unsettled conditions and widespread showers/thunderstorms
from southern Alabama through Georgia and coastal South Carolina.
While there is a degree of uncertainty, a signal arises for an
axis of heaviest QPF to streak across the Gulf Coast into Georgia.
PW values likely continuing at 2-2.25 inches overlapping MUCAPE of
more than 1000 J/kg, rainfall rates of 1-2+ inches/hour are
likely within any convection that develops and then tracks
northeast. This setup may be conducive for some repeating rounds.
A Slight Risk was hoisted for this period for the Florida Panhandle
and west-central Georgia.

...Northern Plains...

The closed mid-level low from the Day 1 period will continue on is northeastward track as it weakens, leaving a lingering boundary in
its wake. Local rainfall rates in excess of 1 inch/hour are
possible, with a secondary surge in convection possible late in
response to 850mb winds reaching 20-30 kts converging into the
region. Rain accumulations during the Day 1 periods will likely
lower FFG across the region, thus there will be isolated excessive
rainfall impacts.

...Northern Rockies...

During this period a shortwave advancing through the Intermountain
West will aid in the amplification of a trough shifting over the
Northern High Plains. In response, this will drive enhanced ascent
into the already broad synoptically forced lift, helping to spawn
a weak wave of low pressure to track into the High Plains by late afternoon/evening. Fairly progressive showers and thunderstorms
will move from the Northern Rockies to the Northern High Plains.
PW anomalies of +1 to +1.5 sigma above the climo mean is forecast,
which may lead to rainfall rates reaching 1 inch/hour sporadically
thus increasing the threat for local flash flooding concerns.

Campbell/Weiss


Day 3
Valid 12Z Tue Aug 05 2025 - 12Z Wed Aug 06 2025

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL IN THE SOUTHEAST...

...Southeast...

Gulf moisture will continue to surge north/northeast over the
stalled west-east orientated frontal boundary. Showers and
thunderstorms will continue across much of the Southeast with the
highest QPF expected to focus over eastern Alabama and central
Georgia where accumulations of 2 to 3 inches will be possible. This
multi-day event will result in lowered FFG and increased threat for
flash flooding. A Slight Risk area was raised for this period
covering eastern Alabama and much of central/northern Georgia.

...Northern Plains and Minnesota...

The upper-level trough and surface frontal system mentioned during
Day 2 will continue to track across the northern tier, shifting
showers and thunderstorms to the east. Guidance is showing areal
averages of 1 to 2 inches across the region with isolated maximums
possibly up to 3 inches, with the higher totals closer in
proximity to the International border. A broad Marginal Risk was
maintained for this period. First guess fields hint a small area
may need a Slight Risk, but confidence on where is low at this time
so opted to stick with just a Marginal for this issuance.

Campbell
$$
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FOUS30 KWBC 040822
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
422 AM EDT Mon Aug 4 2025

Day 1
Valid 12Z Mon Aug 04 2025 - 12Z Tue Aug 05 2025

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR THE SOUTHEAST...

...Southeast...

Wet and unsettled conditions to persist across the Southeast as a
mid-level trough axis lingers to the west allowing for moisture to
stream northeast from the Gulf. The trough draped from the Great
Lakes to the Arklatex will weaken slightly as ridging from the
Atlantic expands northwestward. Heavy rain will spread across the
region as PWs remain 1.75 to 2.25 inches, highest within a narrow
channel from the FL Panhandle into coastal South Carolina,
overlapping MUCAPE that is progged to rise above 1000 J/kg. The
presence of the strong upper level jet will enhance forcing for
ascent over the region while the surface front remains draped
across the region, and a shortwave ejects northeast from the Gulf.
This environment should support expanding showers and
thunderstorms, with just a slight shift Northwest expected in the
axis of heaviest rain due to the expansion of the mid-level ridging
from the east.

Antecedent moisture has lowered FFGs and increased soil sensitivity,
especially for portions of Alabama and Georgia. The Slight Risk
areas was expanded a bit further west into Alabama and
northeastward across Georgia and far western South Carolina. With
rainfall rates likely eclipsing 2 inches/hour at times, any of this
heavy rainfall falling atop these vulnerable soils could quickly
become runoff leading to instances of flash flooding.

...Northern Plains...

Mid-level impulses lifting slowly northeast from the Northern
Plains into the Upper Midwest will weaken Monday. However, forcing
for ascent will continue, despite being in a weaker state, as PVA
from the accompanying vorticity maxima pivots across the area and
interacts with persistent WAA on 20-25 kts of 850mb southerly flow
demarcating the LLJ. This will push PWs to above 1.25 inches, or
around the 90th percentile according to NAEFS. MUCAPE will be
somewhat limited, but the same WAA could drive CAPE to above 500
J/kg, supporting HREF neighborhood probabilities for rainfall rates
above 1"/hr to 10-20%.

In general, cells should be somewhat progressive to the northeast
on 0-6km mean winds of 10-15 kts. However, a region of enhanced
bulk shear nearing 30 kts close to the MN/SD border will also be
within an area of deformation which could result in regenerating
and backbuilding convection. This will lead to slower net motion
and repeating heavy rainfall, which is likely to be the focus of
heaviest rainfall accumulation reflected by HREF 3"/24hr
neighborhood probabilities of 20% (displaced south of the REFS but
seemingly more likely in position). This could occur atop soils
that become primed by rainfall on Sunday, but the excessive rain
risk still appears MRGL so no upgrades appear needed at this time.

...Lower Ohio Valley...

An inverted surface trough is expected to lift northeast today into
the lower Ohio Valley. Low- level convergence along this boundary
will combine with broad thickness diffluence and a shortwave
pivoting northeast to drive pronounced lift into a region of high
PWs (above 1.5 inches) and a collocated plume of MUCAPE above 1000
J/kg. Very weak flow across this area suggests that as convection
blossoms, cells will move slowly, generally from south to north,
with repeating rounds of 1-2"/hour rainfall rates leading to
pockets of 3+ inches of rainfall. The Marginal Risk area was maintained.

...Northern Rockies...

During this period a shortwave trough will emerge from the Pacific
Northwest and track into the Northern Rockies. Impressive ascent,
primarily through height falls and increasing mid-level divergence,
helping to spawn a wave of low pressure tracking into the High
Plains by Tuesday morning. Showers and thunderstorms are expected
to increase in coverage as a response, and with easterly low-level
flow feeding in the higher PW values, rainfall rates of 1
inch/hour or greater will be possible.

Campbell/Weiss


Day 2
Valid 12Z Tue Aug 05 2025 - 12Z Wed Aug 06 2025

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL IN THE SOUTHEAST...

...Southeast...

With the ridge extending into the Atlantic across Florida and the
trough positioned into the lower Mississippi Valley., much of the
environment described during the Day 2 period has not changed.
Between these two features, moisture will continue to surge
northeast beneath shortwave impulses that are being squeezed by
this synoptic pattern. The result of this will be waves of
convection lifting northeast, with rainfall rates of 1-2
inches/hour continuing to be supported despite a modest forecast
reduction in PWs.

THe latest guidance and WPC QPF indicates 2 maxima, one over the
higher terrain of western Carolina/northeast Georgia and the other
over central Georgia. Both locations will have areal average of
roughly 2 inches. Portions of the region have had multi-day
accumulations and will be vulnerable to additional rainfall. The
inherited Slight Risk was adjusted on the northern bounds to the
northeast, covering western parts North Carolina and South
Carolina. AS such, the Marginal Risk area was expanded into
southern Virginia.

...Northern Plains and Minnesota...

Mid-level impulse closing off over Saskatchewan will shed vorticity
downstream to drive height falls and PVA from Montana through North
Dakota and into Minnesota. This mid-level ascent will help deepen a
surface low moving across southern Canada, with triple-point development/occlusion pushing a complex frontal structure
southeastward. Ascent across this area will impinge upon favorable thermodynamics surging northward, especially in the vicinity of the
warm front, leading to widespread showers and thunderstorms
pivoting northeast through the day. PW values of greater than 1.5
inches (between the 90th and 97th percentile according to NAEFS)
and MUCAPE reaching 1000-2000 J/kg, convection should support
rainfall rates of 1-2 inches/hour. There continues to be a fair
amount of spread on the QPF accumulations and overall footprint.
Backbuilding into the higher instability will allow for some
training along the frontal boundaries. Areal averages of 1 to 2
inches possible. The inherited Marginal Risk area was expanded
further south across eastern South Dakota and southwest Minnesota
to encompass the southern end of the convection.

Campbell/Weiss

Day 3
Valid 12Z Wed Aug 06 2025 - 12Z Thu Aug 07 2025

...THERE ARE MARGINAL RISK AREAS FOR EXCESSIVE RAINFALL ACROSS THE
UPPER MISSISSIPPI VALLEY AND FOR THE COASTAL SOUTHEAST AND MID-
ATLANTIC REGION...

...Upper Mississippi Valley...

The features described in the Day 2 period will propagate across
across the northern tier states shifting the areas of precipitation
to the east. Two distinctions cluster of higher QPF is expected
during this period. The first over southern Minnesota and the other
across northern Minnesota/International border where areal averages
of 1-2 inches is possible. A Marginal Risk was maintained for
eastern portions of the Dakotas, most of western/central Minnesota.

...Carolinas and Mid-Atlantic...

By this time, the surface low will be moving offshore taking the
frontal boundary with it and the showers and thunderstorms will
decrease from west to east, lingering over coastal areas. The best concentration of storms and QPF totals will be over coastal Georgia
and southern/central South Carolina. A Marginal Risk spans from
far northeast Florida to central Virginia.

Campbell
$$
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FOUS30 KWBC 050832
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
432 AM EDT Tue Aug 5 2025

Day 1
Valid 12Z Tue Aug 05 2025 - 12Z Wed Aug 06 2025

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE SOUTHEAST AND INTO THE MID-ATLANTIC...

...Southeast and Mid-Atlantic...

A heavy rainfall and flash flood event may be getting started at
the beginning of the period, as convection is expected to increase
in coverage and intensity from northeast Georgia into Upstate
South Carolina (potentially extending into far southwest North
Carolina) this morning. A conducive overall setup for locally heavy
downpours exists, with a low-level front/convergence zone and the
right entrance region of a strong upper-level jet streak
superimposed over the same area (along with anomalously high
moisture and PWs over the 90th percentile). The main limiting
factor for organized heavy rainfall is certainly instability,
though a modestly strengthening low-level jet (15-25 kts) will
provide some isentropic upglide to kick things off this morning
(with hourly totals likely limited to 1-2"). Most hi-res models
depict a break in the precipitation during the day, but another
round may ensue later tonight over some of the same areas, as the
frontal zone and parent trough to the west move very little.

Further diurnally-driven development is expected within the broader
warm sector from the central Gulf Coast to south-central Georgia,
and the rest of South Carolina, with stronger instability building
today with daytime heating and PWs in excess of 2 inches. Hi-res
models continue to indicate fairly high probabilities of 2"/hr
rain rates, and a complex pattern of cell mergers and colliding
outflow boundaries and sea breezes. This may lead to periods of 1-2
hours where convection is maximized in particular areas, and
scattered instances of flash flooding. The inherited Slight Risk
was expanded a bit to cover coastal portions of SC/GA with the
highest probabilities for localized 5" exceedance.

...Northern Plains and Minnesota...

There continues to be a fairly strong signal for storms to initiate
in the northern extent of an instability plume in the Plains, near
the nose of a moisture transport maximum, in the afternoon today.
Consensus among the hi-res models is this will rapidly organize
into an MCS and then likely propagate quickly to the southeast in
the general direction suggested by the thickness contours. The
potential for relatively fast forward motions may mitigate some of
the flash flood risk. However, precipitation anomalies over the
past 14 days indicate the pattern has been relatively wet of late
in the Northern Plains, and precipitable water values will be
anomalously high. Deep moisture combined with strong instability
should support high instantaneous rain rates. Therefore, any areas
where the duration of heavy rain could be lengthened (such as
backbuilding along the periphery of a cold pool, cell mergers with
antecedent convective development) may lead to flash flooding. The
Marginal Risk was maintained and adjusted southward based on the
latest guidance (factoring in upwind propagation favoring southern
propagation late).

...Ohio River Valley...

An inherited Marginal Risk was maintained and adjusted slightly
for a potential repeat of the pattern from yesterday, just
displaced slightly to the east over S IN, C KY, SW OH. A slow
moving mid-level wave is expected to continue to slowly shift
east, in the presence of relatively strong instability. Therefore,
scattered afternoon thunderstorms are expected. Although moisture
levels are not expected to be anomalously high, storm motions
should be very slow with mean winds in the lowest 8-km around 5 kts
or so. This could lead to localized flash flooding by extending the
duration of heavy rain with the most intense storms. Rain rates
should reach the 1-2"/hr range.

Churchill/Lamers


Day 2
Valid 12Z Wed Aug 06 2025 - 12Z Thu Aug 07 2025

...THERE ARE MARGINAL RISK AREAS FOR EXCESSIVE RAINFALL ACROSS
PORTIONS OF THE UPPER MISSISSIPPI VALLEY AND FOR THE COASTAL
SOUTHEAST AND MID-ATLANTIC REGION...

...Upper Mississippi Valley...

A region of anomalously high moisture, with PWs near the 90th
percentile, should shift east during the Day 2 period, and
generally continue to be superimposed with moderate to strong
instability on the periphery of a ridge. Confidence in the
convective details remain low at this time, but the overall
environment will remain supportive of organized convection with
high instantaneous rain rates. The pattern may still lead to a forward-propagating MCS, which would mitigate flash flood risk
overall, but the overall environment is favorable enough to
continue to maintain a Marginal Risk across the region.

...Coastal Southeast and Mid-Atlantic...

Confidence remains relatively low in the placement of the heaviest
rainfall on the Day 2 period, as the ECMWF/ECENS suite continues
to concentrate QPF farther north (mostly across North Carolina)
whereas the bulk of the other global models and ensembles are
focused south and east (mainly in SC and GA). Regardless of the
precise details, a plume of anomalously high precipitable water
values is likely to remain present across the coastal Southeast
and Mid-Atlantic region into the Day 2 period, and the flash flood
threat areas will likely come down to mesoscale details that will
come much more into focus in subsequent outlook periods.

Churchill/Lamers


Day 3
Valid 12Z Thu Aug 07 2025 - 12Z Fri Aug 08 2025

...THERE ARE MARGINAL RISK AREAS FOR EXCESSIVE RAINFALL ACROSS
PORTIONS OF THE UPPER MISSISSIPPI VALLEY AND NORTHERN PLAINS, AS
WELL AS FOR THE COASTAL SOUTHEAST AND MID-ATLANTIC REGION...

...Upper Mississippi Valley and Northern Plains...

An inherited Marginal Risk area was maintained and adjusted across
North Dakota and surroundings, as models are in good agreement in
indicating a potent upper-level shortwave digging southward into
the CONUS by Day 3. The approach of the trough is likely to result
in another wave of low-level return flow into the Northern High
Plains, sending PWs to the 90th percentile or higher once again.
Moderate to strong instability is expected to build once again with
daytime heating on the periphery of a ridge, and organized
convection is likely to ensue in the late afternoon and evening.

...Coastal Southeast and Mid-Atlantic...

Confidence remains low in the placement of the heaviest rainfall
going into the Day 3 period, with substantial differences still
between the global model suites. As anomalously high tropospheric
moisture is likely to remain near the coast, maintained an
inherited Marginal Risk area across portions of the area most
likely to realize heavy precipitation with daytime heating.

Churchill
$$
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FOUS30 KWBC 060817
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
417 AM EDT Wed Aug 6 2025

Day 1
Valid 12Z Wed Aug 06 2025 - 12Z Thu Aug 07 2025

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE COASTAL SOUTHEAST AND SOUTHERN MID-ATLANTIC REGION...

...Coastal Southeast and southern Mid-Atlantic...

Relatively high coverage of convection is expected once again
today, as a stalled frontal boundary remains draped across the
region. While storms should generally remain relatively short-lived
over any one location with shear being the main limiting factor,
more significant convective organization is possible in the
vicinity of the NC/SC Coastal Plain border region where deep layer
shear is progged to be closer to 20-30 kts (versus less than 20 kts
from surroundings). This is due to the slow eastward progress of
the blocked upper trough to the west, and a vorticity maxima may
also contribute to convective proliferation later today via DPVA
and enhanced upper divergence via right-entrance region of ~80 kt
jet streak over the Northeast. While the 00z HREF 5" exceedance
probs are quite high (50%+ over portions of the Coastal Plain),
uncertainty remains high with regard to the extent of resulting
flash flooding, as the QPF spread between the HREF members remains
quite large (with the NAM-nest and FV3 being the wetter outliers,
while the ARW and ARW2 are the drier outliers). Maintained the
inherited Slight Risk, and a targeted upgraded Moderate Risk could
be possible later today should models come into better agreement.

...Central Plains into Middle and Upper Mississippi Valley...

A mature MCS is diving southward early this morning from SD/MN into
IA/NE (see MPD #877 for more information) along with anomalously
high tropospheric moisture (PWs nearing 2.0", or around the 90th
percentile). Maintained a Marginal Risk for lingering convection
associated with the MCS this morning, along with the potential
sustained or redeveloped convection in association with the remnant
MCV later today.

Churchill


Day 2
Valid 12Z Thu Aug 07 2025 - 12Z Fri Aug 08 2025

...THERE ARE MARGINAL RISK AREAS FOR EXCESSIVE RAINFALL ACROSS
PORTIONS OF THE NORTHERN PLAINS, AS WELL AS FOR THE COASTAL
SOUTHEAST AND SOUTHERN MID-ATLANTIC REGION...

...Northern Plains...

Models continue to indicate a potent upper-level shortwave digging
southward into the PacNW by Day 2, and have maintained a Marginal
Risk centered on ND where convection is anticipated to initiate in
the afternoon. The approach of the trough will result in another
round of low-level return flow into the Northern High Plains,
sending PWs to near (or above) the 90th percentile once again.
Moderate to strong instability with daytime heating should yield
organized convection by late afternoon/evening, and a targeted
Slight Risk upgrade may be necessary with subsequent outlooks.

...Coastal Southeast and southern Mid-Atlantic...

Confidence in the rainfall forecast is relatively low going into
Thursday, as much depends on how convection ultimately evolves
today. That said, the recent trends in QPF have been downward with
most models showing anomalously high tropospheric moisture and
low-level convergence shifting to the immediate coastline. Have
maintained an inherited Marginal Risk for this cycle, which may be
further reduced in coverage should these model trends continue.

Churchill


Day 3
Valid 12Z Fri Aug 08 2025 - 12Z Sat Aug 09 2025

...THERE ARE MARGINAL RISK AREAS FOR EXCESSIVE RAINFALL ACROSS
PORTIONS OF THE NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY, AS
WELL AS FOR THE COASTAL SOUTHEAST AND SOUTHERN MID-ATLANTIC REGION...

...Northern Plains into Upper and Middle Mississippi Valley...

Inherited Marginal Risk was expanded to include a relatively large
portion of the north-central portion of the CONUS, a continuation
of the threat from Day 2 from a potent upper trough/closed low.
Convective details remain quite fuzzy at this range, but guidance
suggests the potential for localized 3-5" totals (high spatial
spread in these depictions) which may necessitate future targeted
upgrades.

...Coastal Southeast and southern Mid-Atlantic...

Low confidence forecast continuing into Day 3, maintaining a
Marginal Risk area that is largely focused on the same area. At
this juncture most models depict heavy rainfall remaining largely
offshore, but given recent heavy rains and the potential for
significant amounts today have opted to keep the Marginal Risk.

Churchill
$$
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FOUS30 KWBC 071142
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
742 AM EDT Thu Aug 7 2025

Day 1
Valid 1125Z Thu Aug 07 2025 - 12Z Fri Aug 08 2025

...THERE ARE MARGINAL RISK AREAS FOR EXCESSIVE RAINFALL ACROSS
PORTIONS OF THE NORTHERN PLAINS...UPPER MIDWEST/GREAT LAKES...AS
WELL AS THE SOUTHEASTERN COAST INTO NORTHERN FLORIDA...

...Northern Plains...

The 00Z model consensus shows a potent upper-level shortwave
tracking through the northern Rockies today/tonight with a lead
mid-level impulse out head helping to ignite thunderstorms over
eastern Montana with movement into North Dakota this
afternoon/evening. 00Z GFS forecast standardized anomalies of PW
are +2 to +3 over the northern Plains with moderate to strong
CAPE and increasing upper level divergence/diffluence ahead of the
approaching upper trough. 850 mb winds are forecast to increase
into the 30-40 kt range across SD, ahead of a related surface low,
helping to fuel the potential for multiple rounds of thunderstorms
through the period and some 2 to 4 inch rainfall totals (locally
higher possible). While movement of any organized convective
clusters should be generally be progressive toward the
east/southeast, potential for training will exist on the
southwestern flank and the environment will likely support 1-2
in/hr rainfall rates.

...Upper Midwest...

1124Z Update: Expanded the Marginal Risk area a bit west-southwest
based on the latest observational trends. Veering late-stage LLJ
(southwesterly ~25kts) orthogonal to the elevated frontal boundary
along the northeast periphery of the upper ridge has resulted in
some upscale growth with the backbuilding/training convection across south-central and southeast IA this morning. A bit later than
normal given the nocturnal-diurnal cycle transition, however in
this case the elevated convergence became maximized late given the
orientation of the veering LLJ and the frontal zone. For further
details, please refer to the latest Mesoscale Precipitation
Discussion or MPD #880.

Hurley

Previous discussion...
Thunderstorms are likely to develop during the afternoon hours in
the vicinity of Iowa/Wisconsin/Illinois with weak warm advection
across a subtle theta-e gradient that strengthens with daytime
heating. Moderate to strong instability is forecast to develop from
southern Minnesota into Iowa and points eastward at the nose of a
20 to 30+ kt 850 mb jet axis oriented southwest to northeast into
the Upper Midwest and continue into the first half of the
overnight. While uncertainty remains, indications are for a small
cluster of thunderstorms to form with potential for upstream
development and slow net movement of heavy rain cores. 12Z and
previous 00Z members of the HREF suite showed a relatively large
spread in location and magnitude of heavy rainfall but decent
agreement for at least 3 to 5 inches. Low confidence in location
resulted in a broadening of the previous Marginal RIsk area over Wisconsin/Illinois to include locations to the west, south and east.

...Northeastern Gulf Coast to Coastal Mid- Atlantic...

High moisture will remain across the Coastal Plain of the Carolinas
into the Florida Panhandle today into Friday morning, ahead of a
mid-level trough axis in place over the Southeast and an embedded
vorticity max forecast to move eastward from the southern
Appalachians. Precipitable water values are expected to remain near
2 inches along the coast and into northern Florida.

Thunderstorms will increase with daytime heating and low level flow
from the east to northeast will originate from the higher moisture
airmass. Scattered coverage of thunderstorms is expected across
portions of the Mid-Atlanitc and Southeast with cells exhibiting occasional slow movement and training. The high moisture and sufficient
instability (at least 500 to 1500 J/kg MLCAPE) will be capable of
producing 2 to 3+ in/hr rainfall rates at times, some of which
could fall on urban centers or locations with above average
rainfall over the past week.

Otto


Day 2
Valid 12Z Fri Aug 08 2025 - 12Z Sat Aug 09 2025

...THERE ARE MARGINAL RISK AREAS FOR EXCESSIVE RAINFALL ACROSS
PORTIONS OF THE NORTH-CENTRAL U.S. AND SOUTHEASTERN COAST INTO
NORTHERN FLORIDA...

...Northern Plains into Upper and Middle Mississippi Valley...

There is potential for a lingering MCS to be in place over
Minnesota at the start of the period (12Z Friday). The potent
closed low/upper trough from Thursday night will continue to
advance across the north-central U.S. on Friday/Friday night.
Thunderstorms, some possibly slow moving, are expected to impact
portions of northeastern Montana during the day on Friday while
thunderstorms expand in coverage during the afternoon over North
Dakota into portions of South Dakota. By 00Z Saturday, a cold front
is expected to become better defined over the Dakotas and move into
a fairly unstable and moist airmass from the eastern Dakotas into
Minnesota. Numerous thunderstorms are expected ahead of this
boundary for Friday night, with fairly progressive movement but
potential for training within a strengthening nocturnal low level
jet, out ahead of the front.

...Northeastern Gulf Coast to Coastal Mid-Atlantic...

Eastward movement of the mid-level trough over the Mid-Atlantic
states will allow the higher moisture along the coast to push
offshore but anomalous moisture will remain over Florida (1 to 2
standardized precipitable water anomalies). Sea breeze convergence
along the coast in the Southeast will allow for at least some
potential for flash flooding due to high rainfall rates from
thunderstorms with 2 to 3+ in/hr rates possible. Farther south, low
level easterly flow and a lingering surface boundary are expected
to focus convection from northern Florida into the western
Peninsula during peak heating hours. There will be spotty potential
for 3 to 5+ inch rainfall totals across the coast of the Carolinas
down into portions of northern Florida.

Otto


Day 3
Valid 12Z Sat Aug 09 2025 - 12Z Sun Aug 10 2025

...THERE ARE MARGINAL RISK AREAS FOR EXCESSIVE RAINFALL ACROSS
PORTIONS OF THE CENTRAL PLAINS INTO THE UPPER MIDWEST AND OVER THE
SOUTHWESTERN U.S...

...Upper Midwest...

A cold front will advance eastward into the Upper Mississippi
Valley on Saturday ahead of a strong mid-level trough moving across
the north-central U.S. Standardized precipitable water anomalies of
+2 to +3 are forecast by the 00Z GFS to be in place ahead of the
front over the Upper Mississippi Valley, supporting growing
instability with daytime heating. Unidirectional southwesterly flow
ahead of the front will allow for periods of training with
thunderstorms that form in the pre-frontal environment with
potential for multiple rounds of storms.

...Central Plains...

The cold front will move through the central Plains with low level
upslope flow in its wake over the High Plains region. Precipitable
water values are forecast to be near to slightly above average and
ascent will be aided by the region's placement within the
divergent and diffluent right- entrance region of the upper jet
located on the eastern side of the advancing upper trough axis.
Thunderstorms will likely shift east from eastern Colorado into
Kansas, meeting with an increasing low level jet of 40 to 50 kt
beyond 00Z Sunday. The 00Z model consensus is for an axis of
locally heavy rain stretching from eastern Colorado into Kansas and
southern Nebraska. Current thinking is for some 2 to 4 inch
rainfall totals, most of which could fall over a 2-3 hour window.

...Southwest...

Flow around a mid-level ridge centered over New Mexico should
prompt increasing moisture into the Southwest with precipitable
water values reaching near climatology for early August over
Arizona and New Mexico. Assuming a lack of widespread cloud cover
beneath the ridge should allow for sufficient CAPE generation by
mid-afternoon and typical monsoonal thunderstorm coverage by
evening. The concern for flash flooding will be enhanced by slow
storm motions given 00Z model forecasts of 850-300 mb mean wind
speeds of 10 kt or less.

Otto
$$
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FOUS30 KWBC 080908
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
508 AM EDT Fri Aug 8 2025

Day 1
Valid 12Z Fri Aug 08 2025 - 12Z Sat Aug 09 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER CENTRAL AND
NORTHERN MINNESOTA INTO FAR NORTHWESTERN WISCONSIN...

...Northern Plains through Upper Mississippi Valley...

An anomalous 500 mb low will track eastward from the
Montana/Canada border today with strong height falls moving into
the Dakotas later today and tonight. At the surface, low pressure
over South Dakota will track eastward toward Minnesota today before
advancing into southern Canada overnight as a cold front becomes
more defined to its south. Strong to extreme instability is
forecast again with this system today, ahead of the low/front over central/southern Minnesota along with highly anomalous moisture
over central and northern Minnesota (+2 to +4 standardized
anomalies via 00Z GFS). The front will steadily track eastward
between 00-12Z Saturday but potential will exist for high rainfall
rates given the environment.

An MCS from early Friday morning is expected to continue eastward
into the northern half of Minnesota early in the period but with a
weakening trend as the low level jet weakens and veers. While this
first round of rainfall is not expected to pose much in the way of
a flash flood threat prior to 18Z, high short term rates and
perhaps an inch or so of rain may prime soils for a second round
Friday night. A second round of thunderstorms is expected to form
over eastern North Dakota by late evening with convection
orienting from NNE to SSW with the advancing cold front. Numerous
thunderstorms are expected ahead of this boundary for Friday night
as low level forcing combines with increasing diffluence/divergence
aloft ahead of a jet max east of the upper low. Should line
orientation briefly match the mean steering flow, allowing for
training, high rain rates of perhaps 2+ in/hr can be realized as
the convective axis shifts eastward into northwestern Wisconsin by
Saturday morning. A Slight Risk was introduced for the potential
for flash flooding and potential for 2-4 inches in central to
northern Minnesota. The Marginal Risk surrounds this region for
lower confidence in excessive rainfall potential.

...Southeastern Coast into Northern and Central Florida...

High moisture with precipitable water values near 2 inches (a bit
higher over central/northern Florida) will be in place again today
in the vicinity of a lingering stationary front that extended from
offshore of the Carolinas into northern Florida. Daytime heating
should allow MLCAPE values to rise into roughly the 1000-2000 J/kg
range. Weak mid-level ridging over Florida will be accompanied by
weak deeper layer mean flow, supportive of slow storm motions. 00Z
models support the potential for some slightly stronger low level
flow over the western Peninsula, northeast of an inverted trough
axis in the eastern Gulf, which could increase potential for slow
cell movement/backbuilding. The environment could support rain
rates of 2 to 4 in/hr, but the threat appears rather isolated to
widely scattered, only supporting a Marginal Risk.

Otto


Day 2
Valid 12Z Sat Aug 09 2025 - 12Z Sun Aug 10 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER IOWA INTO
SOUTHERN WISCONSIN AND NORTHWESTERN ILLINOIS...

...Midwest...

A cold front will enter the upper Great Lakes to central Plains and
stall on Saturday as the core of an anomalous 500 mb low tracks
northeastward from south-central Canada. Precipitable water values
of 1.5 to 2.0 inches are forecast by the model consensus to pool
along the front and moderate to strong instability values are
likely to develop with daytime heating. While there may be some
lingering convective activity along the front Saturday morning
across the Upper Midwest, the main flash flood concern is expected
to develop later in the day on Saturday. Backing low level flow is
forecast to setup east of a surface low in Kansas with 30-40 kt at
850 mb forecast by the 00Z model consensus (some guidance is near
50 kt Saturday night). Flow aloft will be divergent and diffluent
to the south of an upper jet max over the upper Mississippi Valley,
enhanced by an upstream shortwave trough forecast to advance
through the central Rockies Saturday night. Increased forcing for
ascent along the front with mean steering flow parallel to the
synoptic front should favor areas of training with heavy rain
likely. While the details are a bit uncertain, the most likely
areas to see heavy rain potential (3 to 5 inches) will be near the
front from Iowa into southern Wisconsin and far northwestern
Illinois where a Slight Risk was introduced with this update.

...Central Plains...

In the wake of a cold front moving into the southern High Plains,
low level upslope into western Nebraska/Kansas and eastern Colorado
will favor increased moisture into the region and sustaining of
thunderstorms forecast to move off of the higher terrain by
Saturday afternoon. MLCAPE is forecast to be at least 1000-1500
J/kg over the High Plains and when combined with sufficient shear
aloft, some organized storms will be possible. There will be
potential for isolated flash flooding late Saturday evening into
the overnight as a low level jet develops, aiding convergence in
the vicinity of the frontal boundary, forecast to return north as a warm front.

...Southeastern Coast into Northern and Central Florida...

A similar setup across the Southeast will set up for Saturday as
was in place for Friday with high precipitable water values over 2
inches in place from the eastern Gulf coast into coastal South
Carolina near a lingering front. Portions of the outlooked area
will have weak steering flow in place yet again and low to mid-
level winds from the east to southeast will favor scattered
thunderstorms during peak heating with potential for brief training/backbuilding and high rates of 2-4 in/hr. At this time,
coverage of flash flood potential looks to be low enough to
warrant only a Marginal Risk.

...Southwest...

The mid to upper-level ridge that will be in place from Friday into
Saturday will begin to break down as upper level troughing
amplifies into the region from the north. Moisture values are
expected to return to near seasonal levels for early August across
Arizona while remaining slightly below average in New Mexico.
Thunderstorms are expected to form with solar insolation along the
higher terrain by 18Z, ramping up in intensity and coverage through
21Z. Given the increase in moisture compared to prior days, storms
should have a better shot of producing 1 to 2 in/hr rates,
especially across the southern half of Arizona and New Mexico where
weaker steering flow will be present as 00Z model forecasts show
850-300 mb mean wind speeds of 10 kt or less.

Otto


Day 3
Valid 12Z Sun Aug 10 2025 - 12Z Mon Aug 11 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER FROM EASTERN NEBRASKA/KANSAS INTO SOUTHERN WISCONSIN/NORTHERN ILLINOIS...

...Central Plains into Upper Midwest...

A quasi-stationary front will be in place from Sunday into Monday,
extending from the Great Lakes into the southern High Plains. The
base of an upper trough axis will be moving overhead through Monday
morning with southwesterly flow downstream along/over the front. An
enhanced low level flow regime will be in place much of the day
across the southern High Plains into the Midwest with potential
for mid-level impulses within the southwesterly flow aiding with
lift across the Plains to Midwest. The parallel nature of the
steering flow and frontal boundary will again favor the potential
for repeating and training of thunderstorms. Multiple rounds of
thunderstorms will be possible with peak flash flood potential
occurring late Sunday evening and overnight as convection moving
off of the higher terrain meets with strengthening low level flow
ahead of the upper trough. Precipitable water anomalies will
generally be +1 to +2 over the Plains with higher values toward the
Great Lakes. Questionable instability values over the Great Lakes
region will limit flash flood potential as the better consensus for
instability will be over southern locations. Model QPF values
seemed to agree with at least 3 to 5 inch potential from the global
guidance and locally higher from the 00Z RRFS and regional CMC.

...Southern Mid-Atlantic Coast to Northeastern Gulf Coast...

A lingering frontal boundary over northern Florida and high
pressure anchored over the northern Mid-Atlantic will maintain
low level southeasterly winds into the southeastern U.S. on Sunday. Precipitable water values of 2.0 to 2.3 inches over the Southeast
and Florida will again support intense tropical downpours as
thunderstorms increase with daytime heating. Low level
southeasterly winds and confluent axes will combine with sea breeze
convergence and other mesoscale boundaries to support scattered
thunderstorms with isolated flash flood potential from 2-4 in/hr
rainfall rates.

...Southwest...

Continued advancing of the base of an upper trough from the central
Rockies into the central Plains and an elongated ridge over
California will favor northwesterly mid-level flow into the
Southwest. While this may reduce moisture availability across the
Four Corners region, low level southerly flow is expected to be in
place over the northern Gulf of California into Arizona, with
westerly flow advecting low to mid-level moisture downstream toward
New Mexico. Meanwhile, the front over the High Plains from
Saturday night is forecast to again sink down to the south with an
upslope flow regime setting up over northeastern New Mexico,
helping to increase low level moisture into the region. Moisture
values for much of central/southern Arizona and New Mexico are
expected to be near average and monsoon thunderstorms are expected
during the late afternoon and evening hours with perhaps greater
coverage than previous days. Typical potential for high short term
rain rates (1-2 inches in an hour or less) will set up with
isolated to widely scattered flash flood potential.

Otto
$$
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FOUS30 KWBC 110823
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
423 AM EDT Mon Aug 11 2025

Day 1
Valid 12Z Mon Aug 11 2025 - 12Z Tue Aug 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
SOUTHERN PLAINS, COASTAL NORTH AND SOUTH CAROLINA AND ACROSS THE FLORIDA...

...Southern Plains...
The active early morning convection currently across portions of
the Southern and Central Plains will likely weaken prior to or
shortly after 1200 UTC Monday. The latest hi res model consensus is
for the next round of convection to then form farther south along
the surface frontal boundary stretching from the Southern High
Plains, northeastward into the Lower MO Valley. No major changes
made to the previous slight risk area, with the current version
fitting well where both the HREF mean and RRFS mean neighborhood
probabilities for 1 and 2"+ amounts are high. PW values will remain
high, 1.5 to 2"+ in the slight risk area. This combined with
favorable upper difluence on the southeast side of the slow moving
mid to upper level trof moving across the Southern Plains, will
support potential for additional heavy precipitation totals. A
period of slow moving/training cells parallel to the frontal
boundary, primarily in the 0000 to 1200 UTC Tuesday period will
support localized hourly rainfall rates of 1"+.

No changes made to the marginal risk area extending farther to the
northeast into the Mid Mississippi Valley and Lower Lakes region.
The HREF and RRFS mean neighborhood probabilities are not as high
for 1 and 2"+ amounts as over the Southern Plains. Localized heavy
rainfall amounts along this portion of the front, are expected to
be to the south of where the heaviest rainfall fell over the past
24 hours from northeast IA, far northwest IL and southern WI. For
these reasons, the threat level was maintained as marginal.

...Northeastern Gulf Coast...
An axis of tropical PW values, 2 to 2.25"+, will push
northwestward in association with mid level shortwave energy moving
across the northeastern Gulf. Active showers likely in this high
PW axis along the immediate central to northeastern Gulf coastal
regions. HREF and RRFS mean neighborhood probabilities are high for
for 1, 2 and 3"+ totals from the Florida Panhandle, west across
far southern AL, far southern MS, southern LA into coastal
northeast TX. A slight risk was maintained across the FL Panhandle
region. The marginal risk was extended westward to cover the high
HREF and RRFS mean neighborhood probabilities across far southern
AL, far southern MS, far southern LA into coastal northeast TX.
There is consensus for potentially two periods of potentially
.50-1"+ hourly rainfall amounts during the day 1 period. The first
early this morning, extending into the post 12Z Monday period,
followed by another uptick in coastal precip intensities in the
early hours of Tuesday, 0600-1200 UTC.

...Coastal South and North Carolina...
The anomalous PW axis moving northwest into the immediate Gulf
Coast day 1 will also remain in place farther to the northeast
from GA into SC and NC. Only some small changes made to the
previous slight risk areas along the SC and NC coasts, extending
the slight risk approximately 50 miles farther northeast along the
NC coast to cover the latest model qpf and higher HREF/RRFS
probabilities. Active showers likely in this anomalous PW axis as
onshore south southeasterly flow persists day 1. There will be the
likelihood of training of precip areas in the south southeasterly
flow, supporting localized hourly rainfall totals of 1-2"+. The
marginal risk area over west central NC was extended approximately
50-100 miles to the north to cover the latest model qpf.

Oravec


Day 2
Valid 12Z Tue Aug 12 2025 - 12Z Wed Aug 13 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE LOWER
LAKES, SOUTHWESTWARD INTO THE MIDDLE MISSISSIPPI VALLEY AND INTO
THE SOUTHERN PLAINS, FROM THE CENTRAL GULF COAST INTO THE
CAROLINAS AND ACROSS PORTIONS OF THE SOUTHWEST...

...Lower Lakes into the Mid MS Valley and Southern Plains...
An axis of high PW values, 1.5-1.75"+ will continue along and ahead
of the elongated frontal zone stretching from the Lower Lakes,
southwestward into the Mid MS Valley and into the Southern Plains.
Scattered convection likely in this high PW axis, supporting
locally heavy precip totals. The previous marginal risk area was
extended farther southwestward from southern MO, across northwest
AR, much of OK and into northern TX to cover model qpf spread. Also
expanded the previous marginal risk area farther northwestward
into eastern WI and the northern portion of the L.P. of MI to cover
the model qpf spread for potentially locally heavy rainfall totals
along the northern portion of the frontal zone across these areas.

...Central Gulf Coast into the Carolinas...
The axis of high PW values stretching from the Central Gulf Coast
into the Carolinas on day 1 will persist across these regions day
2. Shortwave energy embedded in this high PW axis will continue to
support potential for additional heavy rains day 2. The previous
marginal risk area was extended east northeastward from northern
GA/Upstate of SC/far western NC to cover much of the remainder of
NC and SC where several models show heavy rain potential.

...Southwest...
No changes made to the previous marginal risk area from southeast
AZ into much of NM. Weak shortwaves progged to rotate around the
mid to upper level ridge building eastward into the Great Basin day
2, enhancing large scale uvvs in an axis of seasonable PW values.
Scattered convection across this area will support potential for
localized heavy rainfall amounts and isolated runoff issues,
especially across more vulnerable terrain features or burn scars.

Oravec


Day 3
Valid 12Z Wed Aug 13 2025 - 12Z Thu Aug 14 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE LOWER
MISSISSIPPI VALLEY INTO THE TENNESSEE AND OHIO VALLEY AND EASTERN
LAKES, ACROSS COASTAL SOUTH CAROLINA AND COASTAL NORTH CAROLINA,
PORTIONS OF THE NORTHERN PLAINS AND OVER THE SOUTHWEST...

Similar to the day 2 period, an axis of high PW values will
continue to stretch from the Central Gulf coast, east northeastward
into the Southeast and Southern Mid Atlantic. Widespread scattered
convection likely in this anomalous PW axis, values 1.5-2 standard
deviations above the mean. Mid to upper level dynamics will have
weakened by day 3, with less defined areas of upper diffluence to
accentuate lift in this high PW axis. Still, model consensus is for
continued potential for continued locally heavy rains across these
areas. A marginal risk was added for the upper coast of SC and the
lower coast of NC where models do show potential for additional
locally heavy rains day 3.

...Lower Lakes/Northeast into the OH/TN Valley, Central to
Southern Appalachians...
An axis of high PW values, 1.5-1.75"+ also likely to continue
along the elongated frontal zone pushing eastward through the Lower
Lakes into NY State and northern New England and stretching
southwestward into the OH/TN Valley regions and Central to Southern Appalachians. Widespread scattered convection likely along this
front in this high PW axis, supporting locally heavy rains and
isolated runoff issues. No changes made to the previous marginal
risk area along and ahead of this front.

...Southwest...
No significant changes to the overall flow pattern for the
Southwest day 3. Additional weak vorts rotating around the Great Basin/Southwest mid to upper high will support another round of
scattered convection. Low confidence on any qpf details, but
potential will continue for localized heavy rains and isolated
runoff issues, especially across more vulnerable terrain features or burn scars.

...Northern Plains...
The low level southerly flow expected to strengthen after 0000 UTC
Thursday across the Northern Plains ahead of a surface front
emerging into the Northern Plains. An area of organized convection
possible ahead of this front, with locally heavy precip totals
possible. There is a lot of model spread with qpf details at the
moment, leading to low confidence. The previous marginal risk area
was decreased in size to better fit the overlap of potentially
heavy rains with the lower FFG values.

Oravec
$$
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FOUS30 KWBC 120828
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
428 AM EDT Tue Aug 12 2025

Day 1
Valid 12Z Tue Aug 12 2025 - 12Z Wed Aug 13 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
SOUTHERN APPALACHIANS AND PORTIONS OF THE CENTRAL GULF COAST...

...SOUTHERN APPALACHIANS...
There continues to be a strong model signal for heavy rains in the
vicinity of the Southern Appalachians day 1. PW values remain well
above average from the Central Gulf coast, northeastward into the
Southern Appalachians and then eastward through the Carolinas and
Southern Mid-Atlantic. Convection will be enhanced through this
anomalous PW axis by a stream of mid to upper level vorts forecasts
to rotate across this region, around the peripheries of a weak mid
to upper level ridge centered just off the northeast Florida
coast. While locally heavy rains are possible anywhere in this high
PW axis, one strong model signal is across the Southern
Appalachians where moist upslope flow and enhanced uvvs from the
embedded vorts will support heavy precip. The slight risk area was
not changed much from the previous issuance and fits well with the
latest axis of high neighborhood probabilities from the HREF and
RRFS mean for 2"+ amounts. The RRFS mean has a more defined 3"+
high probabilities than the HREF, but both mean still emphasize the
area in the vicinity of the Southern Appalachians for heavy rains day 1.

...Central Gulf Coast...
A slight risk was continued along portions of the Central Gulf
Coast from in the vicinity of Pensacola, west to New Orleans.
Consensus from the latest hi res guidance is for the potential for
two periods of heavy rains affecting the immediate coastal region
in association with the mid level vorts rotating north
northeastward off the Gulf. HREF probabilities for .50 to 1"+
amounts begin to increase prior to 1200 UTC Tuesday and continue to
be high until 1500 UTC across the Central Gulf coast. A second
period of high hourly HREF probabilities for .50-1"+ then occurs
again in the early hours of Wednesday, beginning around 0600 UTC
and continuing to just after 1200 UTC. Isolated runoff issues
possible from each heavy precip max period, especially in more
urbanized regions.

...Great Lakes, Ohio Valley, Mid Mississippi Valley into the
Southern Plains...
A broad marginal risk area was maintained across a large region
from the Great Lakes, south and southwestward into the OH Valley,
Mid MS Valley and Southern Plains. PW values will remain high
across these regions, 1.5 to 2"+, with the latest suite of models
showing at least localized heavy rain potential in this high PW
axis. While HREF and RRFS neighborhood probabilities for 1"+ totals
are high across these areas, the probabilities do drop
significantly for higher totals. The HREF EAS probabilities for 1"+
are low across much of this region, depicting poor overlap with
the hi res heavy rain areas. One exception is over northeast IL
into far northern IN and southwest L.P. of MI where EAS 1"+
probabilities are as high as 25-30%, showing better hi res heavy
rain overlap. The higher EAS probabilities are to the southeast of
where the heaviest rains have occurred recently. This and the
expected progressive nature of the convection, supports keeping
the risk level as marginal.

...Southwest...
No changes made to the previous marginal risk area from southeast
AZ into much of NM. Weak shortwaves progged to rotate around the
mid to upper level ridge building eastward into the Great Basin day
1, enhancing large scale uvvs in an axis of seasonable PW values.
Scattered convection across this area will support potential for
localized heavy rainfall amounts and isolated runoff issues,
especially across more vulnerable terrain features or burn scars.

Oravec


Day 2
Valid 12Z Wed Aug 13 2025 - 12Z Thu Aug 14 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS MUCH OF
THE EASTERN AND SOUTHERN UNITED STATES, AS WELL AS FOR PORTIONS OF
THE NORTHERN PLAINS AND SOUTHWEST...

No changes of note made to the very broad marginal risk area day 2
stretching northeastward from the Central Gulf coast, into the
TN/OH Valleys, Southern to Central Appalachians, Mid-Atlantic into
NY State and northern New England. A broad axis of above average PW
values, 1.5 to 2+ standard deviations above the mean will stretch
along and ahead of the primary surface front moving west to east
across the northern tier from the Lower Lakes/OH Valley region,
east into the Mid-Atlantic/Northeast. The above average PW values
across the Gulf coast into the Southeast/Southern Mid-Atlantic
during day 1, will also continue into day 2. There is general
agreement in the models for the potential for widespread scattered
convection in this high PW axis, with areal average moderate totals
depicted and likelihood of locally heavy totals. Confidence is low
with respect to where the heavier, more concentrated convection may
be. Subsequently, we have not changed the risk level from previous
issuances, maintaining it at marginal for the time being.

A few areas of concern for potential higher threat level day 2 in
subsequent issuances.

Southern Appalachians: Early morning heavy rains late day 1 across
the Southern Appalachians may linger into the post 1200 UTC
Wednesday period across eastern TN/western NC. The HREF 12 hour
neighborhood probabilities ending 0000 UTC Thu Aug 14 are high for
1 and 2"+ amounts.

Mid-Atlantic: Convection likely to begin to become more organized
ahead of the above mentioned frontal boundary pushing eastward.
HREF 12 hour neighborhood probabilities ending 0000 UTC Thu Aug 14
are high for 1 and 2"+ amounts from northern VA, northward across
much of PA into the Southern Tier of NY State.

Central Gulf Coast: HREF hourly precip probabilities for .50-1"+
amounts remain high early day 2 from the expected second round of
heavy rains to affect the Central Gulf coastal region during the
day 1 period, that may extend into the day 2 period.

...Northern Plains...
There continues to be a lot of model spread day 2 with potential
convective development ahead of the next front pushing into the
Northern High Plains 0000-1200 UTC Thursday. The low level
southerly flow expected to strengthen after 0000 UTC Thursday
across the Northern Plains ahead this front, supporting increasing
convective potential. Several of the global models do show
potential for heavy amounts late day 2, but continue to show large
amounts of spread with respect to placement, leading to continued
low confidence. Given this, the risk level was maintained at marginal.

...Southwest...
No significant changes to the overall flow pattern for the
Southwest day 2. Additional weak vorts rotating around the Great Basin/Southwest mid to upper high will support another round of
scattered convection. Low confidence on any qpf details, but
potential will continue for localized heavy rains and isolated
runoff issues, especially across more vulnerable terrain features
or burn scars.


Day 3
Valid 12Z Thu Aug 14 2025 - 12Z Fri Aug 15 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE LOWER
MISSISSIPPI VALLEY, TENNESSEE VALLEY, SOUTHERN APPALACHIANS INTO
THE SOUTHEAST AND ACROSS THE SOUTHWEST AND THE UPPER MISSISSIPPI VALLEY...

...Southeastern portion of the CONUS...
The cold front moving across the northeast tier of the CONUS day 2
will keep the axis of above average PW values, 1.5 to 2+ standard
deviations above the mean, concentrated across the southeast
quarter of the CONUS from the Lower MS Valley, east across the TN
Valley, Southern Appalachians and into the Southeast. There is
general model consensus for widespread scattered convection across
these areas day 3, with locally heavy rains likely where convection
becomes more organized. Large scale uvvs will continue to be
enhanced by shortwaves rotating around the mid to upper level ridge
that is expected to build westward day 3 across North Florida into
the northeast Gulf. Models are showing a lot of spread with qpf
details day 3, keeping the risk level, at the moment to marginal
across these areas.

...Southwest...
Similar to the day 2 period, no significant changes to the overall
flow pattern for the Southwest expected on day 3. Additional weak
vorts rotating around the Great Basin/Southwest mid to upper high
will support another round of scattered convection. Low confidence
on any qpf details, but potential will continue for localized heavy
rains and isolated runoff issues, especially across more
vulnerable terrain features or burn scars.

..Upper Mississippi Valley...
The frontal boundary moving into the Northern Plains day 2 will
continue to push eastward into the Upper MS Valley day 3. There may
be two rounds of precip affecting this area day 3. An initial
surge of warm advection rains early day 3, followed by potential
frontal convection late day 3. Continued low confidence in any qpf
details at this range, warranting only a marginal risk.

Oravec
$$
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FOUS30 KWBC 131251
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
851 AM EDT Wed Aug 13 2025

Day 1 Valid 1244Z Wed Aug 13 2025 - 12Z Thu Aug 14 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS THE SOUTHERN
AND CENTRAL APPALACHIANS...NORTH TEXAS AND THE IMMEDIATE CENTRAL
GULF COAST...

1245Z Excessive Rainfall Discussion...
Issued a special Excessive Rainfall Outlook to hoist Slight Risks
in the northern portion of Texas where convection has been growing
upscale in intensity and areal coverage. Latest short-range
CAM guidance showed some 3 to 5 inch rainfall potential here which
seems consistent given the potential for some back-building
convection. Refer to WPC Mesoscale Precipitation Discussion 924.
Also introduced a Slight Risk area along the Gulf coast...mainly
over the Florida peninsula...where an area of showers and
thunderstorms has been dropping locally intense downpours.
Additional details in the WPC Mesoscale Precipitation Discussion
923. Only other change was to extend the pre-existing Slight Risk
in the Central and Southern Appalachians southwestward into parts
of southern Tennessee and northern Alabama based on latest trends
in radar imagery.

Bann

...Southern Appalachians...

A cold front over the Great Lakes to mid-Mississippi Valley early
Wednesday morning is forecast to advance southeastward into New
York, the central Appalachians and western Kentucky/Tennessee by
Thursday morning. High moisture with precipitable water (PW)
anomalies of 1 to 2+ are forecast to extend ahead of the cold front
from central Texas to western New England and much of the East
Coast. Across the southern Appalachians, there may be an early
round of locally heavy rainfall early Wednesday, related to
lingering nocturnal convection. The greater concern will be later
today with peak afternoon heating and scattered coverage of
thunderstorms, ahead of a synoptic scale mid-level trough axis
approaching from the northwest and a low to mid- level impulse
tracking around a ridge offshore of the Southeast, with some
locally enhanced southerly flow into the Appalachians. 00Z HREF and
18Z REFS neighborhood probabilities of exceeding flash flood
guidance (FFG) were a bit higher here than other areas of the U.S.
with potential for some 2-4 inch totals (locally higher) through
Thursday morning.

...Remainder of Eastern U.S. into Lower Mississippi Valley...
Confluent and locally stronger 925-850 mb winds of 20-30 kt are
expected across Virginia/North Carolina as the region sits between
ridging to the south and troughing to the north today. There will
be some enhanced potential for training and backbuilding cells in
the west to east flow, coupled with PWs over 2 inches, supporting
potential for a few 3 to 5 inch totals.

Back toward Texas and much of the Lower Mississippi Valley, high
PWs and slow storm motions could support some widely scattered
instances of flash flooding during peak heating, with dissipation
into the overnight.

...Northern Plains...
A few thunderstorms will be possible over South Dakota in the
first 6 to 9 hours of the period, ahead of an advancing mid-level
impulse tracking eastward from southeastern Montana. Nocturnal
strengthening of the low level jet is expected overnight, ahead of
a shortwave approaching from the west, with southerly winds of 35
to 45 kt at 850 mb forecast by the 00Z GFS through the central
Plains into the Dakotas. A small MCS is possible near a warm front
across the region overnight but details on exact location and
rainfall totals remain a bit uncertain. The Marginal Risk covers
the probabilities for 2+ inches highlighted in the 00Z HREF and 18Z REFS.

...Southwest...
A ridge aloft over the Four Corners region is forecast to slowly
shift east into eastern New Mexico by Thursday morning, ahead of an
approaching upper trough into California. Some increase in PWs are
expected into Arizona and southwestern New Mexico during the period
but values will climb to near average by 00Z Thursday. An
expectation of decent solar insolation with limited cloud cover
should support seasonable instability values into the region for
this afternoon/evening and Localized flash flooding will be
possible with diurnally driven thunderstorms, especially across
more vulnerable terrain features or burn scars.

Otto


Day 2 Valid 12Z Thu Aug 14 2025 - 12Z Fri Aug 15 2025

...THERE ARE MARGINAL RISKS OF EXCESSIVE RAINFALL FROM THE LOWER
MISSISSIPPI VALLEY TO THE MID-ATLANITC COAST AND NORTHEAST...AS
WELL AS THE SOUTHWEST AND THE UPPER MISSISSIPPI VALLEY...

...East Coast to Lower Mississippi Valley...
The cold front from Wednesday will continue to advance toward the
southeast with lingering high moisture ahead of the boundary from
New England into the Mid-Atlantic Coast. Potential for localized
excessive rainfall within the anomalous PW axis and with forcing
ahead of the front, but cloud cover may limit the potential for
higher instability values. There should be at least an isolated
flash flood threat with thunderstorms ahead of the front from
southern New England to the Mid-Atlantic coast.

Farther south, from the Southeast to the Lower Mississippi Valley,
there does not appear to be a substantial focus area for excessive
rainfall potential, hence the broad Marginal Risk, but high
moisture and daytime heating will result in scattered thunderstorms
with peak rainfall rates in the 1 to 3 in/hr range. Similar to
Wednesday, parts of the Lower Mississippi Valley will have high PWs
and slow cell motions given placement between a mid- level ridge
center over KS and another over the northeastern Gulf.

...Southwest...
The upper trough over California on Wednesday will continue to move
east on Thursday with increased moisture advection into Arizona and
parts of Utah into the Four Corners region. PW values are forecast
to increase to near +1 standardized anomaly for Arizona into
southern Utah. While cloud cover is a bit uncertain for Thursday
into Friday, ahead of the western trough and from any lingering
disturbances from the previous day, A similar sized, perhaps
slightly larger, Marginal Risk is drawn for Thursday into Friday
following the model QPF consensus and Arizona Regional WRF
simulated reflectivity, which showed the potential for more
widespread coverage of thunderstorms on Thursday compared to Wednesday.

..Upper Mississippi Valley...
A cold front will move into the north-central U.S. on Thursday with
a steady enhancement to southerly/southwesterly 850 mb winds ahead
of the boundary. Even after diurnal weakening of the nocturnal low
level jet, 00Z GFS forecasts show 20-40 kt continuing from the
central Plains into the eastern Dakotas and Minnesota through
Thursday evening. Locally heavy rain may be ongoing Thursday
morning with decent potential for another round Thursday night with
favorable jet diffluence/divergence aloft, possible moderate
instability and standardized PW anomalies of +1 to +2. Confidence
on the exact location remains uncertain however, with hopefully
increasing confidence occurring as we move into the hires range.

Otto


Day 3 Valid 12Z Fri Aug 15 2025 - 12Z Sat Aug 16 2025

...THERE ARE MARGINAL RISKS OF EXCESSIVE RAINFALL FROM THE LOWER
MISSISSIPPI VALLEY TO THE SOUTHEAST COAST...AS WELL AS THE
SOUTHWEST/FOUR CORNERS REGION AND THE UPPER MISSISSIPPI VALLEY...

...Southeast Coast to Lower Mississippi Valley...

Lingering high moisture will be in place on Friday, south of a
southward sagging frontal boundary with standardized PW anomalies
of +1 to +2 from the Lower Mississippi Valley to the Southeast
Coast. With an upper ridge centered over the northeastern Gulf,
there will be potential for mesoscale impulses to ridge around the
ridge and help focus diurnally driven thunderstorms during peak
heating. Similar to previous days, locally high rain rates with 1
to 3 in/hr may occur with localized training.

...Upper Mississippi Valley...
A cold front will continue to advance downstream through the Upper
Mississippi Valley but slow/stall back toward the west. PWs will
remain above average in the vicinity of the front and organized
thunderstorm potential will exist within the mean westerly flow
aloft. Similar to previous days, nocturnal strengthening of the low
level jet at night will have the potential to generate an MCS or loosely-organized convective cluster with localized training
potential. Confidence is rather low at 3 days out, but the Marginal
Risk was drawn to cover the various model solutions and conceptual
thinking for greatest rainfall potential near the front and low
level jet axis intersection.

...Southwest...
Active southwesterly flow across much of the western U.S. will
encourage the further expansion of above average moisture into the
Four Corners region and northern Great Basin. While standardized PW
anomalies will generally peak in the +1 to +2 range, not everyone
within these anomalies will see the same flash flood potential. The
focus appears to be best tied to the Mogollon Rim into the Wasatch
and central to southern Rockies, ahead of a number of shortwave
impulses moving in from southern California. Tied to the relatively
stronger belt of westerlies could be jet-induced divergence maxima
aloft to help in the production of locally heavy rainfall.

Otto
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