FOUS30 KWBC 150809
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
409 AM EDT Tue Jul 15 2025

Day 2
Valid 12Z Wed Jul 16 2025 - 12Z Thu Jul 17 2025

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

...Gulf Coast...
A tropical wave (now up to 40% chance of development from NHC) will
continue to track slowly westward across the northern Gulf as the
mid-level vorticity center remains trapped beneath an elongated
ridge to the north. This will force the wave to track almost due
west on Wednesday, but there remains quite a bit of latitudinal
spread amongst the various global models as to where the vorticity
center will track. This causes lowered confidence in the QPF and
subsequent ERO for Wednesday, as the ridge to the north combined
with generally weak shore-parallel 850mb flow (at least until the
shortwave passes west of each area on the coast) could severely
limit the amount of rain that can penetrate onshore. However,
convection that does develop onshore will benefit from PWs above
2.25 inches (potentially approaching 2.5 inches) and MUCAPE of 2000
J/kg, supporting rainfall rates above 2"/hr. With some training
along the coast likely, this could produce 2-3" of rainfall in some
areas, although the exact placement of the heaviest rain is still
uncertain. At this time the MRGL risk remains for the Gulf Coast,
but if this system organizes more quickly or models form a
consensus for a more northward track, a SLGT risk may be needed
eventually for Wednesday.

...Central High Plains eastward through the Mid-Atlantic...
Broad and expansive mid-level ridge centered off the Carolinas will
continue to dominate the synoptic pattern with return flow around
this ridge promoting a continuation of the exceptional moisture and
instability plaguing much of the CONUS. Wednesday will be no
exception as a moisture plume characterized by PWs of 1.5 to 2.25
inches stretches from Kansas through New England, coincident with
pools of MUCAPE exceeding 2000 J/kg. Within this axis of impressive thermodynamics, a stationary front from Monday will dissipate as a
secondary front approaches from the Northwest late Wednesday night. Additionally, within the mid-level return flow, multiple shortwave
impulses will rotate northeast around the ridge to provide
additional ascent. Where these impulses interact with the low-level
baroclinic boundary, enhanced rainfall from more organized
convection will result.

This is most likely in two areas on Wednesday. The first is across Pennsylvania/Ohio where a potent shortwave impulse is progged to
track overhead during peak heating. This will not only drive
locally enhanced ascent, but also accelerate bulk shear to 30-35
kts forcing better storm organization. 850mb inflow across this
area will also strengthen, potentially reaching 30-35 kts which
will be 1.5 times the mean 0-6km wind, a signal for strong
convergence. Although storms that develop should remain progressive
to the east, multiple rounds are likely, each one containing
rainfall rates of around 2"/hr, leading to total rainfall of 2-4"
in some areas. This falling atop saturated soils from recent heavy
rainfall will likely result in instances of flash flooding.

The other area will be across the Central Plains and Upper Midwest,
especially focused from northern Kansas through Wisconsin where a
multiple MCS driven by convectively enhanced shortwaves will move
across these areas with focused heavy rainfall. ALthough there
continues to be some latitudinal spread with the placement of these
MCSs which will be the primary driver of the flash flood risk D2,
a slowly veering 30-40kt LLJ emerging from the Southern Plains will
provide the focus for development through convergence and
isentropic lift. Through this veering late Wednesday night, some training/backbuilding is also anticipated (Corfidi vectors point
directly against the mean flow by 06Z Thursday) suggesting enhanced
rainfall totals from rates that will be 1-2"/hr if not locally
higher. The inherited SLGT risk was modified for the new guidance
and positioned across the best overlap of REFS (where available),
GEFS, and ECENS 3"/24hr probabilities exist

...Desert Southwest...
Increasing PWs on southerly low-level flow emerging from the Rio
Grande and Mexico is expected again on Wednesday, with PWs surging
to as high as 1.5 inches over southern Arizona. This is higher and
more expansive than what is progged for D1. However, with the
expected widespread convective coverage continuing late Tuesday
night into Wednesday morning, re-destabilization may be limited,
which is reflected by degraded CAPE > 500 J/kg probabilities from
the GEFS that are below 40% except along the immediate NM/AZ
border. Additionally, forcing for ascent through shortwave activity
appears displaced a bit farther north and less intense as Tuesday,
so while any storms that develop Wednesday would be slow moving and
have brief 0.5+"/hr rates, the MRGL risk category was maintained.

Weiss

Day 3
Valid 12Z Thu Jul 17 2025 - 12Z Fri Jul 18 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE CENTRAL
GULF COAST...

...Gulf Coast...
A disturbance moving across the northern Gulf (NHC probability of
development 40%) will continue to drift westward on Thursday. While
there is still considerable temporal and spatial spread among the
various models, it is likely that a weakness will develop around
the Atlantic ridge to allow a slow NW drift of this feature towards
the LA coast on D3. With PWs expected to be 2.25 to 2.5 inches, and
forcing for ascent intensifying as the system consolidates, heavy
rainfall rates of 2+"/hr will be likely within convection/heavy
stratiform rain. Despite uncertainty as to how far north the
precipitation will spread by 12Z Friday due to subsidence/drier
air to the north within the ridge, a consensus of the guidance
still pushes some heavier focused rainfall into southern LA,
prompting the SLGT risk from around Mobile Bay, AL to the LA/TX
border. Additional adjustments are likely as the forecast becomes
refined in the next few days.

...Central Plains through the Northeast...
Return flow around an elongated Atlantic ridge which will spread as
far west as the Southern Plains will maintain broad SW winds and a moist/unstable environment across a large portion of the country.
Into this favorable environment, a cold front will slowly push
southeast, extending from New England to the Central High Plains by
the end of the period. Ascent along this front into the robust
thermodynamics will support at least scattered thunderstorms with
heavy rain rates. At this time the signals for any organized
convection leading to a higher flash flood risk is muted, so a
broad MRGL risk remains. However, with weak impulses moving through
the flow and interacting with the baroclinic zone, it is possible
some areas may be upgraded to SLGT risks with future issuances as
guidance converges on any locally enhanced rainfall threats.

...Southwest...
Elongated ridge from the Atlantic will spread westward into the
Southern Plains and Four Corners, while a closed low pushes north
from Baja into southern California. Between these two features,
southerly flow will become pinched, while weak impulses embedded
within the flow drift northward. PWs will climb to broadly above
1.25 inches, highest in AZ, but the environment at this time
appears to be lacking sufficient instability for widespread
monsoons thunderstorms. Still, the southerly flow, high PW, and
weak impulses aloft will support convection, especially where flow
upslopes into terrain features. Storm motions will be slow, and
rain rates above 0.5"/hr are probable, so isolated flash flooding,
especially in vulnerable terrain or across burn scars/urban areas,
is possible.

Weiss
$$


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FOUS30 KWBC 160816
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
416 AM EDT Wed Jul 16 2025

Day 2
Valid 12Z Thu Jul 17 2025 - 12Z Fri Jul 18 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE CENTRAL
GULF COAST AND PORTIONS OF THE FOUR CORNERS STATES...

...Gulf Coast...
All eyes will be on Invest 93L for which NHC has placed a 40%
chance of development across the northern Gulf. The guidance is
converging on the track of this invest, although uncertainty
remains high as the system has not developed yet. Still, there is
increasing confidence in the track of this system, and the mid-
level circulation should begin to track NW on Thursday into a
weakness which develops in the ridge to the north. This will allow
for more widespread precipitation to spread onshore as the northern subsidence/dryness begins to erode and the accompanying tropical
moisture plume pivots northward. This will support training of
tropical rain showers lifting into Louisiana, with rainfall rates
2-3"/hr supported by deep column saturation noted in forecast
soundings and PWs approaching 2.5 inches. Additionally, forecast
soundings indicate that the mean winds through 300mb are quite
weak, and this indicates that if the system can organize more
quickly and intensify, low-level moist inflow could quickly exceed
the mean wind to enhance ascent, which would additionally create
more widespread heavy rainfall. GEFS and ECENS probabilities both
indicate a low-end risk (10-15%), as does the LREF from DESI, but
this may under-forecasting the true threat in the tropical
airmass, as several deterministic models show 3-6" across southern
Louisiana on Thursday. At this time opted to maintain the SLGT risk
for this area, but should the system begin to organize and models
converge on a more aggressive solution, an upgrade may be needed
for D2 (a MDT risk is already in effect for D3).

...Central Plains through the Northeast...
A cold front will sag slowly southeast, pushed by a broad but
subtly amplifying trough along the Canadian/United States border.
This trough will impinge into broad mid-level ridging which will
remain elongated west from the Carolinas, leading to pinched flow
generally aligned WSW to ENE from the Central Plains into the Mid-
Atlantic and Northeast. Through this pinched mid-level axis,
multiple vorticity impulses are progged to cross from west to east,
each one interacting with the low-level baroclinic boundary to
enhance ascent leading to scattered to widespread thunderstorms.

Convection which develops on Thursday will likely contain intense
rain rates as thermodynamics in the vicinity of this front remain
impressive. PWs are progged to exceed 2 inches, which is above the
90th percentile from NAEFS, and be collocated with a MUCAPE axis of
2000-3000 J/kg, or higher. These intense thermodynamics will
support rainfall rates that could reach 2-3"/hr (as high as 30%
chance from the HREF through 00Z Friday), with cell training likely
as 0-6km mean winds align parallel to the front. Additionally, bulk
shear magnitude of 20-30 kts will support storm organization,
especially beneath any of the more powerful impulses moving through the flow.

While at this time there is no clear signal, and hence
too much uncertainty, for any local SLGT risk areas, it is possible
that some targeted SLGT risk upgrades may be required with later
issuances. This would be most likely across parts of KS/MO where a
morning MCS decays and leaves a lingering boundary to enhance
thunderstorms with training, or potentially farther east into the
Ohio Valley/Central Appalachians where training atop more sensitive
soils may occur.

...Four Corners...
Elongated ridge extending from the Carolinas through the southern
High Plains will interact with a closed low lifting northward from
Baja into southern California on Thursday. This will squeeze
intensifying deep-layer southerly flow out of Mexico and the Gulf
of California, driving impressive moisture advection northward into
the Southwest. PWs within this plume will exceed 1.25 inches as
IVT surges above the 90th percentile, at least locally, according
to NAEFS, but collocated MUCAPE is progged to be modest as
reflected by SREF 500 J/kg probabilities peaking around 40% in AZ,
although higher across northeast NM. While many of the
deterministic models predict at least scattered convection during
the day, the heaviest rainfall may be across northern AZ/northern
NM as the 850mb inflow convergences into weaker wind speeds, which
is more effectively overlapped by upper diffluence to enhance
ascent. This suggests that the current MRGL risk is still
appropriate for most of the area, however, a targeted SLGT risk has
been collaborated for northeast NM and far Southeast CO where a
vorticity lobe lifting N/NE will interact with the greater
instability and the tail end of the lingering front to provide a
focus for more organized convection.

Weiss


Day 3
Valid 12Z Fri Jul 18 2025 - 12Z Sat Jul 19 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR THE CENTRAL GULF COAST...

...Gulf Coast...
Concern for flash flooding Friday revolves around Invest 93L which
will likely begin its turn to the NW, regardless of how it
develops. While guidance has tended to back off on the intensity
and associated precipitation with this feature, there continues to
be a lot of uncertainty into this forecast and NHC has maintained a
40% chance of development over the next few days. Regardless of
development, the associated tropical moisture plume will support
heavy rainfall rates of 2-3"/hr, with some training likely on the
upwind side of this feature. The GEFS and ECENS ensembles are
modest with the rainfall Friday(only 10% chance for 3" of rain),
but after coordination with the affected WFOs, the MDT risk was
maintained with only minor cosmetic adjustments for consistent
messaging and the potential if this system does become more organized.

...Mid-Mississippi Valley...
A stationary front Thursday will gradually lift northward on
Friday, moving across the Mid-Mississippi Valley and into the Upper
Midwest. This boundary will surge north in response to both the
expanding ridge to the southeast and an intensification of the
850mb LLJ reaching 30+ kts out of the Gulf and returning through
the southern Plains. At the same time, a shortwave impulse,
potentially convectively reinforced from prior thunderstorms, will
move along the front to enhance ascent, resulting in an axis of
thunderstorms which may congeal into an MCS Friday night. There
remains some uncertainty into both the placement and speed of this
MCS, but PWs elevating to above 1.75 inches and MUCAPE pushing
above 3000 J/kg will support rain rates of 1-2"/hr, if not locally
higher. This could produce more than 3" of rain where any training
can occur, and the SLGT risk was tailored to best match the GEFS
and ECENS probabilities for 3"/24hrs.

...Southwest...
An active monsoon day is expected Friday as a potent vorticity
maxima lifts northward over the Four Corners, embedded within
pinched southerly mid-level flow between a ridge to the east and
closed low over southern CA to the west. The key difference in the
evolution of the synoptic pattern Friday is a push west of the
mid-level ridge, which should deflect higher moisture westward,
noted by a plume of 1.25" PWs lifting into southern NV, coincident
with a dramatic increase in SREF CAPE>500 J/kg probabilities as far
as southern UT. There is a lot of uncertainty in the potential for
convective coverage on Friday, but increasing bulk shear and
chaotic/weak storm motions will result in at least an isolated
flash flood risk as storms contain rainfall rates above 0.5"/hr. It
is possible, as well, that a targeted SLGT risk may be needed for
portions of the area with later issuances.

...Central Appalachians and Mid-Atlantic...
A cold front and wave of low pressure will dig slowly southward
from the Great Lakes into the region on Friday. This front will
move into an environment that will be favorable for heavy rainfall
noted by PWs above the 90th percentile according to NAEFS
collocated with MUCAPE of 1000-2000 J/kg. This will likely result
in scattered to numerous thunderstorms developing during the
aftn/eve, with rain rates of more than 2"/hr possible at times. The
guidance is highly variable both with the placement of the
strongest convection, as well as whether or not it can organize
beyond typical pulse type thunderstorms. Due to the uncertainty, no
SLGT risk has been raised at this time. However, increasing bulk
shear Friday evening and the potential for training along the front
could result in 2-3" of rain with locally higher amounts as
reflected by SREF/GEFS probabilities. If this occurs atop the most
vulnerable soils from recent rainfall, a targeted SLGT risk may be
needed for portions of the region.

$$
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FOUS30 KWBC 170814
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
414 AM EDT Thu Jul 17 2025

Day 2
Valid 12Z Fri Jul 18 2025 - 12Z Sat Jul 19 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
CENTRAL GULF COAST, MID-ATLANTIC, AND THE UPPER MIDWEST...

...Central Gulf Coast...

The center of circulation of a tropical disturbance over south-
central Louisiana will stall out early Friday morning and turn
north through much of the Day 2/Friday period. Much of the guidance
and the official rainfall forecast have 2 distinct maxima of total
rainfall Friday and Friday night: One is over western Louisiana,
with a second into the Mississippi and Alabama Gulf Coasts. While
these are maxima, in most cases rainfall amounts will hold between
2 and 4 inches for the day. As mentioned in the Day 1/Thursday ERO
discussion, the tropical disturbance will simply be too weak and
disorganized to support sustained convection for more than a few
hours. Despite help from daytime heating and with ample atmospheric
moisture, without a well-defined source of forcing, the guidance
and the forecast generally agree that the convection will be highly disorganized in clusters that are most likely to track over those
two aforementioned maximum areas, but could just as easily form in
other areas, rain heavily, then collapse and weaken. New storms may
form in similar areas, but once again they will remain widely
scattered. PWATs of 2.25 inches and higher will still support any
storms that can form to be capable of short bursts of very heavy
rainfall of 3+ inches per hour. The disorganized nature of the
storms may still support multiple separate clusters moving over the
same unfortunate area, resulting in highly localized double digit
rainfall totals. However, it is impossible at this point to
pinpoint any one area that is likely enough to see 6+ inches of
rain in a large enough area to continue to paint it in a Moderate
Risk area. Thus, while it remains likely localized areas will see
enough heavy rain to cause localized flash flooding, some of which
may be significant, the threat for numerous flash flooding has
continued decreasing due to the disorganized nature of the
disturbance as a whole. Thus, given the paltry signals for heavy
rain that are highly changeable, the inherited Moderate Risk for
western Louisiana was downgraded with this update.

Meanwhile, further east into coastal Mississippi and Alabama,
these areas east of the center of circulation will be under a
predominant southerly flow of deep tropical moisture. With the
center of circulation drifting northward through the period, expect
nearly stationary "bands" of very heavy showers and thunderstorms
to develop as early as the predawn hours Friday. Any "bands" will
have embedded thunderstorms with much heavier rain in between
lighter showers. Given any heavy rain in these areas from the Day
1/Thursday period will likely have saturated the soils in these
largely urbanized areas, the higher likelihood for additional heavy
rainfall into Friday will only worsen the localized flash flooding
threat from Gulfport east through Pensacola, including Mobile. A
higher end Slight is in effect for this area.

...Mid-Atlantic...

A new Slight Risk area was introduced with this update from central
Virginia southeast through the Tidewater and into northeastern
North Carolina with this update. Disturbances from prior
thunderstorms over the Appalachians will track ESE across this
region on Friday. Ample moisture and instability remain in place
from multiple days of showers and thunderstorms over the past few
weeks. Thus, much of this region has very saturated soils that
cannot handle much additional rainfall. Given the front stalled
over this region will act as a focus, the storms will likely form
over western VA and WV, then track southeastward across the Slight
Risk area and into the Carolinas. Additional thunderstorms are
likely to impact eastern areas prior to that, resulting in
multiple rounds of storms impacting the same area in some cases.
While the storms will be fast-moving, which may limit the time of
the heavy rain over any one area, the likelihood of training and
backbuilding thunderstorms could still result in multiple hours of
heavy rain over some areas, resulting in locally significant flash
flooding, especially were this to occur over any urban area.

...Upper Midwest...

Building southerly flow into a stalled out front will result in
scattered convective development over far southern Minnesota and
northwestern Iowa Friday afternoon. While the storms are in their
formative stage...slow movement and cell mergers could result in
widely scattered instances of flash flooding. The storms are likely
to congeal into a line in eastern Iowa, which will increase in
forward speed as the line races southeast into Illinois by Friday
night. Once the line has formed, the flash flooding risk should
decrease since the line will track orthogonal (southeastward) to
its orientation (southwest to northeast). Soils are at or above
average for this time of year in the area, so the heavy rainfall
likely in this area will support any flash flooding due to
excessive runoff.

Wegman


Day 3
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 MID-ATLANTIC...

Multiple rounds of thunderstorms are likely to impact areas from
Iowa southeast to the VA/NC coast on Saturday. Thunderstorms
ongoing from the Friday night period may impact the Ohio Valley and
central Appalachians Saturday morning. With daytime heating
additional storms will form over much of Virginia, as lines and
other congealing storms move into the Appalachians. Meanwhile an
upper level shortwave will support repeating thunderstorms from
Iowa southeast through Indiana from Saturday afternoon through
Saturday night. All of these are likely to occur over the same
areas hit with strong thunderstorms capable of heavy rainfall on
previous days. Further, the remnants of the tropical disturbance
over the northern Gulf will further add to the moisture available
for storms to use to produce heavy rain over the Midwest. Thus, in
some instances where repeating storms occur, it may not much matter
how saturated the soils are, as the prolonged heavy rain will
result in flash flooding by overcoming the areas where soils are dry.

The Slight Risk area was expanded into southeastern VA and northern
NC with this update. While confidence isn't quite as high on
D3/Saturday as compared with D2/Friday, the signal for heavy rain,
if reduced from Friday, will still support flash flooding in these
hard hit areas.

...Lower Mississippi Valley...

The inherited Slight Risk area over northern Louisiana was
downgraded to a Marginal with this update. There is good agreement
in the guidance that any remnants of the northern Gulf tropical
disturbance will be dissipated by Saturday, with only showers and
isolated thunderstorms remaining over Louisiana, posing only a
Marginal flash flooding risk at most. The downgrade was
coordinated with SHV/Shreveport, LA forecast office.

Wegman

$$
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FOUS30 KWBC 210812
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
412 AM EDT Mon Jul 21 2025

Day 2
Valid 12Z Tue Jul 22 2025 - 12Z Wed Jul 23 2025

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

...Northern Plains/Upper Midwest...

Synoptic scale evolution over the northern tier of the CONUS will
lead to a continued unsettled weather pattern with another round of
heavy convection likely to encompass the eastern Dakotas through
parts of the Upper Midwest. A strengthening upper jet over Canada
coupled with shortwave progression from the southwest and budding
LLJ over the Plains/Midwest will lead to a robust axis of
convection running west to east along a bisecting warm front
approach from the south with another cold front slowly migrating
southeast out Canada. As the flow begins more strongly veered
within the boundary layer, the approach of the front and shortwave
trough will lead to the mean flow becoming more parallel to the
frontal boundary leading to more uni-directional mean layer winds
and back-building prospects as Corfidi Upshear forecast shifts
sharply out of the north with weaker storm relative motions. This
is indicative on plenty of the numerical guidance in the vicinity
of north-central MN over into northwest WI and the Arrowhead. The
concern in the setup is the exact positioning of where this back- building/training axis will transpire as the latitudinal
positioning of the front will make all the difference in where the
heaviest precip will occur and maintain over the back half of the
forecast period. Consensus is still riddled with uncertainty on the
specifics, but the probability fields do note the higher potential
being located along and north of I-94 across ND and western MN.
Greatest threat for significant training seems to be building on a
line from Fargo-Duluth and eventually towards Marquette (More on
that area in the D3 discussion below).

QPF maxima between 4-6" with perhaps a few spots higher when
assessing the different deterministic seems to be the signal as of
now, but we are still only touching the surface of the CAMs.
Considering the environmental parameters (PWATs, instability,
kinematic forcing), the threat is likely well-within the SLGT risk
category with prospects for heavier QPF output as we move closer.
In any case, the SLGT from previous forecast was relatively
maintained with some adjustments on the southern flank of the risk
to note a little more uncertainty in those areas. It's an evolving
setup that could see some shifts in the higher risk area with even
potential for a localized upgrade if consensus on the heaviest
precip axis builds.

...Southeast...

Elevated PWATs and instability across the Southeastern CONUS will
maintain a posture of widely scattered thunderstorms capable of
locally enhanced rainfall rates between 2-4"/hr that could spur
flash flood prospects through the course of Tuesday. A weak surface
reflection along the SC coast with a weak quasi-stationary front
aligned west to east across the Southeast will lead to enhanced
regional convergence that could allow for slow-moving heavy
thunderstorms to train over any area in proxy to these features for
a few hrs. These are the types of setups that can provide a sneaky
3-6" maxima in any given location, especially near the low pressure
center along the coastal plain. Surface trough extending off the
southern flank of the low will likely bisect southeast GA down
through northern FL with guidance consistently pinning a more
defined heavy precip axis within the confines of this area. FFG's
remain very high across that specific area, so the threat for
widespread flash flooding is very low, especially when considering
the probabilities for >5" are still running <20%, a signal
necessary for more appreciable impacts to occur in these zones. In
any case, some of the output from the CAMs is robust locally, so
the threat still falls within the MRGL risk category. The previous
MRGL risk was generally maintained to reflect the persistent
signal, albeit modest at best.

...Southwest...

Another period of monsoonal type convection will enhance localized
flash flood prospects across eastern AZ and much of NM/CO.
Persistent moisture advection along the western flank of a ridge
positioned across the Mississippi Valley will be the driver for the
threat as scattered showers and thunderstorms will litter the
Southwestern CONUS by Tuesday afternoon, carrying through the
evening hrs. Any area within the confines of the above regions will
have a threat for impacts due to convective cores likely producing
rates >1"/hr with upwards of 2"/hr in the strongest cells. Areal
QPF average is generally between 0.25-0.75", but neighborhood probabilities
for >1" over eastern AZ into NM/CO are well above 70% with >2"
probs running between 40-70% over the more terrain favored areas in
both locations. This is more than sufficient for a broad MRGL risk
encompassing these areas with a possibility of a targeted upgrade
if the heavier QPF signals grow within the CAMs in the coming 24 hrs.

Kleebauer


Day 3
Valid 12Z Wed Jul 23 2025 - 12Z Thu Jul 24 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER THE ARROWHEAD
OF MINNESOTA, NORTHERN WISCONSIN, AND THE WESTERN U.P. OF MICHIGAN...

...Upper Midwest...

The progression of convection from the prior D2 will bleed over
into the front half of D3 with the cold front slowly migrating
eastward allowing some advancement of the organized convective
pattern to spill over into the Arrowhead of MN and adjacent
northern WI and western U.P. There's a better consensus on this
occurring given the aligning mass fields from relevant
deterministic, as well as an agreement on the pattern progression
as the surface low over the northern plains finally lifts northeast
along the front and clears into the northern lakes by Wednesday
afternoon. The cold front will still be slowly pushing eastward
through the second half of the period with guidance indicating
another wave of low pressure potentially enhancing the convective
pattern across the Upper Midwest into the northern Great Lakes.
There's a growing consensus on overlap of the two convective
periods to occur over the far northern tier surrounding Lake
Superior with multi-round QPF forecasts indicating a regional max
positioned over the areas referenced above. A SLGT risk was added
across those respective zones due to confidence in the front end of
the forecast period, but maintained a broad MRGL surrounding with
extension back west where the second round is forecast. There's
still some time to delve into the final details on potential
upgrades across parts of the Plains and Upper Mississippi Valley,
so stay tuned for updates in future forecast packages.

...Southeast...

A slowly westward migrating upper trough off the Southeast coast
and attendant surface low over the northern Gulf will lead to
locally heavy rainfall prospects from the central Gulf coast over
into Florida. The signal for rainfall exceeding 3" can be found in
various deterministic leading to a threat for at least urbanized
centers due to higher run off capabilities. The overall pattern
remains very wet with the greatest instability confined to the
immediate Gulf coast with a secondary maxima over inland central
FL. A MRGL risk remains positioned over the above zones given the
threat with the greatest potential for any upgrades likely over the
immediate central Gulf coast.

Kleebauer
$$
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FOUS30 KWBC 220809
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
409 AM EDT Tue Jul 22 2025

Day 2
Valid 12Z Wed Jul 23 2025 - 12Z Thu Jul 24 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
MINNESOTA, NORTHERN WISCONSIN, AND THE WESTERN U.P. OF MICHIGAN...

...Upper Midwest...

The progression of convection from the prior D2 will bleed over
into the front half of D3 with the cold front slowly migrating
eastward allowing some advancement of the organized convective
pattern to spill over into the Arrowhead of MN and adjacent
northern WI and western U.P. There's a better consensus on this
occurring given the aligning mass fields from relevant
deterministic, as well as an agreement on the pattern progression
as the surface low over the northern plains finally lifts northeast
along the front and clears into the northern lakes by Wednesday
afternoon. The final 12hrs of the HREF blended mean QPF output was
pretty clear in a heavy precip presentation across northern WI
through the U.P with the focus likely along and south of the
southern lake shores of Superior. Deterministic depictions are
upwards of 2-4" in additional QPF spilling over from the previous
forecast period leading to some 24hr totals from 00z Wed to 00z Thu
running upwards of 4-5" over the western U.P and northern WI. This
would entice the threat for flash flooding due to the anticipated
rates between 1-2"/hr with higher intra-hour rates expected given
the favorable environment of PWATs >2".

The cold front will still be slowly pushing eastward through the
second half of the period with guidance indicating another wave of
low pressure potentially enhancing the convective pattern across
the Upper Midwest as we move into Wednesday evening. There's a
growing consensus on heavy precip redeveloping across the central
and northern plains between NE/SD and migrating east-northeast
along and ahead of the slow-moving cold front. With flow remaining
parallel to the boundary across a majority of the cold front
positioning, heavy convection with some back-building/training
evolutions are favored which would undoubtedly lead to, at least
some scattered flash flood concerns. The highest probabilities sit
firmly over northeast NE up through the southern half of MN where
ensembles delineate the most favorable proxy of the cold front. QPF
means are running between 1-2" from Minneapolis down towards Omaha
with the prob fields off the latest ECENS and EC AIFS Ensemble
depicting the highest threat across southwest MN towards
Minneapolis with the second round of convection. This was enough to
extend the previous SLGT risk further to the southwest to cover for
the threat with even some potential for extend further back into NE
if the consensus grows and/or magnitudes of rainfall increase
further. This window (00-12z Thu) will need to be monitored closely.

...Southeast...

A slowly westward migrating upper trough off the Southeast coast
and attendant surface low over the northern Gulf will lead to
locally heavy rainfall prospects from the central Gulf coast over
into Florida. The signal for rainfall exceeding 3" remains very
spotty within the varying deterministic, however the threat remains
for isolated heavy convection anywhere along the South Carolina
coast down through the northern half of the FL peninsula over into
the central Gulf coast. Overall, the threat remains on the lower
end of the MRGL risk category, but environment and proximity of
favorable surface pattern maintains the threat for a few robust
cells that could easily overproduce with PWAT forecasts firmly
above 2.25" with some of the coastal plain likely to see PWATs
exceeding 2.5" at times.

...Central and Southern Rockies...

Ample moisture, instability and weak mid-level perturbations in
proximity to the Continental Divide will lead to slow-moving bouts
of convection that will amplify heavy rain prospects that could
induce flash flooding. Terrain complexity and the slow-moving
nature suited by lackluster mean flow and cell anchoring over the
topography spell for a sneaky flash flood risk across the central
and southern Rockies with a general maxima positioned across CO,
west of I-25. A MRGL risk exists for the threat, but if signals
within the CAMs continue to grow as we move closer to the threat
window, a targeted upgrade is not out of the question. For now,
have maintained continuity with the MRGL and will await for the 12z
CAMs output as they will have the full D2 output/prob fields to
assess for the threat.

Kleebauer


Day 3
Valid 12Z Thu Jul 24 2025 - 12Z Fri Jul 25 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL PORTIONS OF THE
CENTRAL AND HIGH PLAINS, MIDWEST, AND SOUTHEASTERN U.S...

...Central Plains to Great Lakes...

Cold front progression and sheared mid-level shortwave ejecting out
of the Rockies will become an integral part in enhancing regional
convective output from the Central Plains up through the Great
Lakes. The environmental parameters such as favorable
thermodynamic properties (Elevated MUCAPE), weak mid-level forcing,
and sfc-850mb convergence in correlation to the front will provide
enough of a mechanism to drive scattered to widespread areas of
thunderstorm activity capable of producing localized flash
flooding. Good news is the models have the threat in question. The
bad news is the consensus on where is pretty much up in the air.
The most favorable areas in the ensemble means are across the
central Midwest back into the Central Plains with a secondary
maxima focused across the Great Lakes. The prospects for a SLGT are
relatively high within the bounds of the broad MRGL risk, but the
threat for scattered flash flood concerns is very much warranted
with the signal.

...High Plains...

Another closed low off CA will allow for a broad diffluent mid and
upper level regime with a multitude of smaller shortwaves migrating
northeast out of the Four Corners. Scattered convective pulses will
likely transpire over the Front Range down along the Continental
Divide. Any area within these bounds could be subject to heavy
precip with a potpourri of individual deterministic outputs
signaling the threat for 2-3+" in any location. Not enough of an
organized area to produce anything more than a broad MRGL risk
encompassing the above areas, so maintained continuity from previous forecast.

...Southeast...

Low pressure along the central Gulf coast will entice yet another
period of heavy convective potential from LA back into FL/GA. PWATs
remains very high (>2.25") for the period with ample instability
situated along the Gulf coast and areas just inland. This is a
prime setup for somewhere to see over 5" of rainfall in a spot, but
the question of exactly where is very much up in the air. Just
assessing the SLP positioning, the best threat is likely over
Southern LA, mainly along and south of I-10. This is a signal
within multiple global outputs, and coincides with the best
convergent winds on the northern side of any surface circulation.
In any case, still kept the previous MRGL inherited just due to the
lack of a discernible organized maxima, but don't be surprised to
see a targeted upgrade somewhere along the central Gulf coast as we
inch closer to the time frame of interest.

Kleebauer
$$
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FOUS30 KWBC 230811
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
411 AM EDT Wed Jul 23 2025

Day 1
Valid 12Z Wed Jul 23 2025 - 12Z Thu Jul 24 2025

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

...Upper Midwest...

Increased confidence in heavy rainfall is forecast across a good
portion of the Upper Midwest with the latest 00z HREF mean QPF
distribution heavily focused over east-central MN across into
northern WI and the western Michigan U.P through the period.
Expectation is for an initial round of convection forming upstream
over the Dakotas into northwestern MN, migrating east-northeast
within the general mean flow the first 6 hrs of the forecast, a
carryover from the previous D1. Isolated flash flood prospects
will be feasible during this initial wave of precip, but the
pattern takes a turn for potentially higher impacts as the surface
cold front to the north begins pressing further southeast through MN/WI.

Expecting a secondary cluster of thunderstorms to develop
over south-central MN up into northern WI in the early afternoon
hrs., spurred on by a strong theta_E advection regime forming along
and south of the cold front as it begins to fan out more west-
southwest to east- northeast once down near the latitude of
Minneapolis-St. Paul. 00z CAMs are bullish on a broad development
of heavy thunderstorms within the confines of the front with
relatively slow cell motions thanks to the mean flow aligning
parallel to the boundary. A deep moisture presence running between
2-3 standard deviations above normal and wet bulb zero heights
between 13.5-14k ft MSL will enable more efficient warm rain
processes with embedded convective element, an environment
suitable for rainfall rates between 1-3"/hr with some intra-hour
rate potential >4"/hr at times as signaled within some of the
individual deterministic. HREF neighborhood probabilities took a
larger step into more robust depictions of the potential with the
latest >3" signal now firmly between 50-70% from east-central MN
across into north-central WI. This alignment also includes the
greater Minneapolis metro and areas along and north of I-94 within
both MN/WI. This area is one of the more prone spots in the
northern CONUS for flash flooding due to the urban footprint and
locally higher run off capabilities. This signal is prevalent for
much of northern WI with convection basically aligning downstream
and prevailing through much of the afternoon and evening before the
front finally sweeps through and carries the threat more into WI
and the Michigan U.P.

There's growing concern of the upstream evolution also becoming
more suitable for widespread convective development generated by
the ejection of a stronger mid-level shortwave into the Central
Plains providing ample ascent within the diffluent area downstream
of the mean trough. CAMs are in and out on the proposed convective
evolution, mainly spatial coverage with some of the CAMs very
bullish which would exacerbate precip potential downstream over NE
into southeastern SD and southern MN/northern IA. This is setup can
tough to figure out at leads, but the mass fields involved are very
much capable of producing a secondary area of heavy precip, even
bordering on significant if you believe some of the hi-res deterministic.

Overall, the combination of favorable thermodynamics and upper
forcing brought on by right-entrance region dynamics from a
strengthening upper jet over Canada will combine to produce
widespread heavy rainfall with a lean towards locally significant
impacts, especially along and north of the I-94 corridor. Totals
between 2-4" with locally as high as 6" are forecast within the
Upper Mississippi Valley up towards the shores of Lake Superior. As
a result, a high end SLGT is forecast from south-central MN and
points northeast, including; Minneapolis/St. Paul, Duluth, Eau
Claire, and the western Michigan U.P. SLGT risk encompasses much of
the Upper Midwest, extending back to the southwest through parts of
the Central Plains thanks to the prospects of a secondary heavy
convective episode that could very well gain more traction as time moves on.

...Florida and the Coastal Southeast...

The active pattern across the Southeast CONUS will continue through
Wednesday with a generally smaller convective footprint compared to
the previous period, but enough to warrant a continued MRGL risk
for locally heavy rainfall. Weak upper trough carrying a formidable
tropical airmass will pivot eastward along the Central Gulf coast
leading to PWATs encroaching 2.25-2.5" consistently from LA over
into the northern half of the FL peninsula. Ascent pattern is
fairly tame with the lack of sufficient jet dynamics, but the
combination of a weak surface reflection migrating southwest from
off the GA coast into the northeast portion of the Gulf will aid in
some enhanced low-level convergence capable of heavy convection
firing and maintaining foothold over places like the northern FL
peninsula and along the immediate Central Gulf coast. Signals are
relatively weak for prospects of >5" (<20%), but there is a decent
enough threat for upwards of 5" which is more than feasible
considering how little effort it will be for any convective
elements to produce 2-3"/hr rates given the favorable buoyancy and
deep moisture presence. Any cells that train or hold ground for any
length of a few hrs. could spell for locally significant rainfall
which could induce flash flood concerns, even away from urban
centers. The previous MRGL risk was maintained with only minor adjustments.

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

Another active period on tap with scattered to widespread
convective development anticipated across the Central and Southern
Rockies through the adjacent High Plains on Wednesday afternoon and
evening. PWATs remain very high (90-97th percentile according to
NAEFS anomalies) across the central High Plains with a bit less a
deep moist axis in-of the Rockies. Even with the less emphatic
signature over the terrain, a slew of smaller mid-level
perturbations within a shortwave trough located over the Front
Range, as well as increasing upper ascent ahead of a deeper upper
trough centered off CA will allow for ample convective initiation
across NM up into CO with a consensus on the greatest coverage
along the Continental Divide. The aforementioned shortwave over the
Front Range will be the disturbance that kicks off yet another
convective cluster over northeast CO with advancement to the
northeast as it follows the mean flow. A relatively good agreement
on a regional max over that area of northeast CO into southern NE
with neighborhood probs running between 40-70% for at least 2" in
this corridor. FFG's in these areas are somewhat high compared to
areas well downstream, so the ability to take a decent hit of heavy
rainfall is better leading to lower chances for widespread flash
flood prospects. Still, it's an area to monitor for short term
upgrades if the signal becomes more prolific for higher totals. NM
coverage will be less than the previous period, so isolated to
widely scattered flash flood concerns lean more to a broad MRGL
risk as well with the extension into CO.

Kleebauer


Day 2
Valid 12Z Thu Jul 24 2025 - 12Z Fri Jul 25 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM THE CENTRAL
PLAINS INTO THE MIDWEST...

...Central Plains to Upper Midwest...

The previous forecast maintains a consistent signature for heavy
rainfall in-of the Central Plains up through portions of the
Midwest. The pattern is being driven by stout ridging over the
Southeastern CONUS extending up into the Mississippi and Ohio
Valleys with a cold front gradually gaining latitude as it pushes
through the Plains and Midwest. Frontal positioning and very
anomalous moisture (PWATs between 90-99th percentile according to
the latest NAEFS) will aid in the persistence of heavy convection
developing and training within the confines of the front leading to
rainfall totals locally exceeding 3" in areas from KS up through
the southwest side of Lake Michigan. There's a growing consensus
within the ensemble means of the corridor of heavy precip generally
aligned southwest to northeast where the front will be located, a
classic signature for training given the expected mean flow to be
parallel to the front for a majority of the period. 00z EC AIFS
ensemble has continued to trend upward in its mean QPF output
across KS into MO where the deepest moisture presence is noted as

2" PWATs are running between 80-100% in the prob fields from all

three HREF/ECENS/EC AIFS Ens. from central KS up through
northwestern MO. This is the area of greatest concern for highest
totals due to the environmental factors at play with rates likely
to top 2"/hr in the strongest convective cores during the period.
Enough of a signal was present to extend the SLGT risk further
southwest to account for the better probabilities for >1" within
the ensemble with a continuation of the SLGT to the northeast as
heavy rain is likely to occur over northern IL towards the
Chicago/Milwaukee corridor.

...Central High Plains and Central and Southern Rockies...

Isolated to widely scattered convection will initiate, once again
across the Front Range back into the Central and Southern Rockies
with localized maxima likely contributing to a few flash flood
prospects in their wake. The primary ascent is still within that
diffluent area ahead of the closed reflection over CA through the
forecast period. Enough of a deep moisture presence and modest
instability up through the Continental Divide and points east will
be suitable for another day of convection with the best opportunity
for flash flooding likely located in proximity of the complex
topography centered over northern NM through CO and southeast WY. A
MRGL risk was relatively unchanged from previous forecast
highlighting the threat.

...Southeast...

The presence of a slow-moving surface reflection and eastward
progressing upper trough across the northern Gulf will lead to
another period of heavy rainfall within the confines of the
Southeast CONUS. Greatest opportunity will lie along the central
Gulf coast where the proximity of the surface low and attendant
surface trough could allow for short periods of convergence in-of
areas along and south of I-10 from LA back into the western FL
panhandle. Guidance remains inconsistent on any organized
convective placement with a smattering of heavy QPF bullseyes
anywhere along the Gulf coast with even some extending back up
through the GA and portions of the Carolina's. With PWATs remaining
up inside the 90-99th percentile along the immediate coast and
suitable instability presence, the previous MRGL was maintained
with general continuity.

...Northern California and Adjacent Areas...

A narrow tongue of elevated moisture on the northern periphery of a
closed upper reflection along the CA coast will lead to a period of
convective development within the northern Sierra's through
northern CA and southern OR. PWATs running ~1 standard deviation
above normal and MUCAPE between 500-1000 J/kg should be sufficient
for scattered convective initiation along the ridges which could
easily produce local 1+" of precip in a short time. Given the
favorable pattern into the terrain still dealing with remnant burn
scars and complex drainage, the risk for at least isolated flash
flooding still has merit. The previous MRGL risk was generally
maintained with only minor adjustments.

Kleebauer


Day 3
Valid 12Z Fri Jul 25 2025 - 12Z Sat Jul 26 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
MIDWEST AND OHIO VALLEY...

...Midwest and Ohio Valley...

Persistence within the upper pattern and a slowly trudging cold
front over the Midwest and Ohio Valley will lead to yet another
period of heavy convective development across the Mid-Mississippi
Valley to points east, mainly in the confines of the front. General
consensus within the means on there being a more defined convective
element over IL through IN and western OH on Friday into possibly
early Saturday morning. A sheared mid-level vorticity maxima is
forecast to meander over the region with the frontal positioning
likely the focal point for convective development/maintenance.
Surprisingly, there is a pretty good signal in the global
deterministic for between 2-4" of rainfall in spots within the
above area, but the placement of course is subject to the exact
frontal positioning. The greatest moisture anomalies between 2-3
deviations above normal will likely be centered in-of the Ohio
Valley with the maxima somewhere along I-80 and points north when
looking at ensemble depictions and various ML. The environment will
be more than capable of continuing the theme of higher rates
between 2-3"/hr at times, so any training could spur flash flood
concerns during any time frames of impact. First Guess Fields have
a SLGT risk situated over IL into IN for the D3, aligning well with
the current proxy of highest QPF being forecast in the means. This
was enough to warrant a SLGT risk upgrade from the Mississippi
Valley over into portions of the Ohio Valley.

...Gulf Coast...

Our disturbance across the northern Gulf will continue to slowly
migrate to the west with an attendant surface low remaining
situated just south of the west-central Gulf coast. Low center
proxy will be the ultimate factor in the prospects of very heavy
rainfall along the immediate Upper TX coast back into LA. So long
as the low center remains far enough offshore, the greatest low-
level convergence pattern and persistent area of convection could
remain just off the coast to limit impacts. However, the airmass
surrounding the disturbance will still be pretty robust with PWATs
remaining very high (>2.3") for much of the immediate coastal plain
over TX back through the central Gulf coast. The National Hurricane
Center has introduced a 10% within the latest Tropical Weather
Outlook over the northern Gulf for the next 3-5 days, so any
tropical characteristics from this disturbance could enhance flash
flood prospects further, especially when it moves closer to the
Upper TX coast. For now, a broad MRGL where PWATs remain high and
ensembles indicate some convective posture is in effect as we keep
a watchful eye on the threat.

...Northern Plains...

A quick moving shortwave ejecting out of the Rockies is forecast to
impact the Northern Plains on Friday night into early Saturday with
scattered thunderstorms likely to roll through the Dakotas after
sunset. Increased regional PWATs upwards of +2 deviations along
with ample mid-level forcing will be enough for a period of
enhanced heavy rainfall prospects during the time frame of impact. Deterministic output is all over the place in exact convective
placement and magnitude, however signals for 2-4" of rainfall in a
short period of time would be sufficient for at least low-end MRGL
prospects up across parts of the Dakotas. Timing of the shortwave
will be key for the threat, but there was enough consensus on their
being a chance for a maintenance of the MRGL risk inherited.

Kleebauer
$$
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FOUS30 KWBC 240804
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
404 AM EDT Thu Jul 24 2025

Day 2
Valid 12Z Fri Jul 25 2025 - 12Z Sat Jul 26 2025

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

...Central Plains into Ohio Valley...

The combination of robust moisture and the presence of both a
surface low progression out of KS and a slow-moving cold front will
lead to yet another day of heavy rainfall across portions of the
Central Plains into the central part of the Midwest. Guidance has
been struggling to ascertain how the this period will evolve, but
the past 00z NWP has come into a bit better agreement on some of
the ingredients that would lead to another round of heavy rainfall
in-of central and eastern KS and points northeast. The key will be
the migration of the surface low across KS. At this juncture, it's
pretty likely the low center will move into northeast KS by Friday
morning with ongoing convection, potentially with some MCV driven
components that would lead to a relatively active beginning of the
D2. Even if convection trends down for the initial 6hr window,
general diurnal destabilization around the low will lead to another
round of thunderstorm genesis in proximity to the surface
reflection and points northeast. This puts a higher threat for
overlapping days of heavy convection across northeast KS into
northwest MO in the first 12hr period before focus shifts northeast
into IA as the low lifts northeast around the northwestern
periphery of the ridge. Any additional rainfall over the KS/MO area
could spell trouble if the D1 works out to how some of the CAMs are
indicating. The trend is leading to further compromised soils and
perhaps even remnant flooding if another round of heavy rain breaks
out not long after impacts from the previous evening.

The threat for rainfall totals between 2-4" with locally higher
maxima across northeast KS, northwest MO, and southern IA is
gaining steam with an unwavering signal the past 5 runs from the
AIFS ensemble QPF distribution. Granted, convective schema is hard
to pin down at leads, but the synoptic progression would favor
heavy precip across these areas with even some inference of heavy
convection through northern IL and IN thanks to the environment in
place along the front. A SLGT risk was extended back west and
southwest for the growing signal with a high end SLGT forecast
across the aforementioned 3 zones in KS/MO/IA. This period could
have some short term shifts pending convective evolution in the D1,
so stay tuned for future updates.

...Gulf Coast...

The disturbance across the northern Gulf will continue to slowly
migrate to the west with an attendant surface low remaining
situated just south of the west-central Gulf coast. Low center
proxy will be the ultimate factor in the prospects of very heavy
rainfall along the immediate Upper TX coast back into LA. So long
as the low center remains far enough offshore, the greatest low-
level convergence pattern and persistent area of convection could
remain just off the coast to limit impacts. However, the airmass
surrounding the disturbance will still be pretty robust with PWATs
remaining very high (>2.3") for much of the immediate coastal plain
over TX back through the central Gulf coast. The National
Hurricane Center is maintaining a 10% within the latest Tropical
Weather Outlook over the northern Gulf for the next 2-3 days, so
any tropical characteristics from this disturbance could enhance
flash flood prospects further, especially when it moves closer to
the Upper TX coast.

...Northern Plains...

A quick moving shortwave ejecting out of the Rockies is forecast to
impact the Northern Plains on Friday night into early Saturday with
scattered thunderstorms likely to roll through the Dakotas after
sunset. Increased regional PWATs upwards of +2 deviations along
with ample mid-level forcing will be enough for a period of
enhanced heavy rainfall prospects during the time frame of impact. Deterministic output is all over the place in exact convective
placement and magnitude, however signals for 2-4" of rainfall in a
short period of time would be sufficient for at least low-end MRGL
prospects up across parts of the Dakotas. Timing of the shortwave
will be key for the threat, but there was enough consensus on their
being a chance for a maintenance of the MRGL risk inherited.

Kleebauer


Day 3
Valid 12Z Sat Jul 26 2025 - 12Z Sun Jul 27 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE GREAT LAKES, OHIO VALLEY, NORTHERN PLAINS, WESTERN AND CENTRAL GULF
COAST, NORTHEAST CALIFORNIA AND NORTHWEST NEVADA...

...Midwest through Great Lakes...

Disturbance across the Plains will move northeast into the Midwest
and eventually the Great Lakes with heavy rain prospects carrying
through the region. This is marking the end of a persistent heavy
rain setup for the past several days with guidance indicating the
highest potential over IA, northern IL and southern WI. Ensemble
trends have shifted to places along and north of I-80 seeing the
greatest potential for 2+" of rainfall at any point in the D3
period, however there's still some uncertainty on specifics of
where the heaviest core of precip will occur when assessing
individual deterministic, so the current MRGL forecast was
sufficient for this time. That said, there's a good chance we will
see an upgrade at some point in the next series of updates, but
details will need to be ironed out on the previous periods of
convection before initiating the upgrade.

...Gulf Coast...

The remnants of the migrating upper trough and surface low 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. Models are truly all over the place when it comes to the
convective expanse during the D3 time frame with some guidance
having little development to others showing a formidable mass of
precip over LA and the Upper TX coast. In any case, the deep
tropical moisture presence and general instability will be pretty
high across the immediate Gulf coast with the ML outputs relatively
favorable for at least scattered heavy convection along and south
of I-10. In coordination with local WFO's across the central and
western Gulf coast, maintained a MRGL risk with emphasis on the
immediate coastal plain where instability points to more favorable
heavier precip potential.

...Northern Plains...

A second potent shortwave will eject northeast out of the northern
High Plains with another round of heavy precip potential with more
organized convective clusters migrating through the Dakotas.
Signature has bounced around on the exact placement of the multi-
cell organization, but probabilities from the latest NBM and AIFS
Ensemble indicate more of northeastern ND as the primary area of
interest. Look for local 2-3" maxima, at the very least with this
type of setup. The good news is the pattern looks relatively
progressive, so outside some near term mesoscale trends for
repeating cell action, the threat remains firmly in the MRGL risk stance.

...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. Modest instability 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. Precip maxima will be limited to ~1",
so the threat lies within the lower threshold of a MRGL risk, which
is what is now forecast.

Kleebauer
$$
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FOUS30 KWBC 311953
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
353 PM EDT Thu Jul 31 2025

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 AND NORTH/NORTHEAST TEXAS...

...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 Friday and 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%.

Only minor adjustment to the previous outlook was to reduce the
northern portion of the SLGT and MRGL based on southern trends in
the progression of the cold front. 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...

The cold/stationary front continues to stretch westward towards the
southern Plains along with PW values near 2" Friday into Friday
night. While most activity should remain pulse-like, a surface wave
and meandering MCV could trigger locally heavy rain in
northern/northeast TX Friday night. The location remains somewhat
uncertain, but this area is highlighted by the 12z HREF as having
6-hr probabilities for >5" at 30-40%. Additionally, the RGEM and
ECMWF included elevated QPF values above 2-3" with the 12z runs in
a very similar location. This potential collocated with the
Dallas- Fort Worth metro led to enough confidence for a targeted
Slight Risk. Expect refinements in future outlooks as more CAM runs
become available and/or the MCV at play becomes more trackable.

...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 inches/hour across
the Dakotas. There is also the potential for an MCV across the
Dakotas to provide a focus for locally intense rainfall, but the
location of this heavy rain remains too uncertain for an upgrade to
a Slight Risk. This potential will be evaluated in future outlooks.

Snell


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 the Lowcountry South Carolina, southern
Georgia and far northern/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. Location in
heaviest rainfall remains too uncertain for an upgrade to a Slight
Risk at the moment and MCS activity may bode too progressive for
widespread flash flooding, thus the region is covered by a Marginal Risk.

Snell/Campbell
$$
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FOUS30 KWBC 022000
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
400 PM EDT Sat Aug 2 2025

Day 2
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 from Saturday will continue to waver along the Gulf
Coast as a stationary front Sunday 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 Sunday evening, but flatten at the same time in response to
an elongated ridge draped across the Gulf. Moisture pooled along
this front will remain impressive as PWs remain 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
eclipsing 2"/hr at times (HREF 50-60% chance) supported by warm
cloud depths nearing 15,000 ft to produce efficient warm-rain
collision processes.

Late in the aftn and into the evening, a shortwave is progged to
rotate beneath the trough and pivot E/NE from the FL Panhandle into
eastern GA, coincident with a surge in bulk shear up to 35 kts.
This could support some more widespread convection with
organization 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"/24hrs and locally a 40-70% chance of more than 5"/24hrs. This
rain will be falling atop areas that will likely receive
significant rainfall on D1 as well, further enhancing the threat
for flash flooding. Although this region generally takes a lot of
rainfall to flood, the setup appears to support a higher than
typical SLGT risk especially from the FL Panhandle through coastal GA.

Otherwise, scattered thunderstorms with intense rain rates could
produce instances of flash flooding on Sunday. The guidance has a
secondary area of maximum rainfall potential along a westward
advancing surface trough through northern AL into central TN which
may require an upgrade in the ERO with later issuances since
3"/24hr probabilities peak at 40-50%, but this correlated with 3-hr
FFG exceedance that is just 10-15%. At this time opted to maintain
the MRGL risk and re-evaluate with new guidance for a possible
upgrade overnight or on the D1 Sunday.

...Plains...
The elongated stationary front aligned north to south from MT
through TX will weaken Sunday, but leave at least 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.

While there is considerable spread and thus uncertainty in the
placement of any of these MCSs, each of them will likely contain
intense rain rates of 1-2"/hr (locally higher) in response to
meridional 850mb flow drawing elevated thermodynamics northward.
From TX to MN a ribbon of PWs of 1.25 to 1.75 inches will overlap a
plume of MUCAPE above 2000 J/kg and bulk shear of 25-35 kts to
support the intense rainfall rates. 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. Uncertainty is high in where this is most
likely, but the REFS and HREF suggest a slightly higher potential
from north Texas into central KS, as well as across portions of
eastern SD/ND into Minnesota.

The large inherited SLGT risk for TX/OK/KS was cosmetically
adjusted, but further refinements are likely (with a reduction of
category also possible) as confidence in MCS placement becomes more
clear. Across MN, a targeted SLGT risk was considered where HREF
and REFS probabilities for 5"/24 hrs peak above 15% as storms
slow/regenerate beneath a deformation axis downstream of a mid-
level closed low. Confidence is modest across this area, but 24-hr
LPMM from the HREF is 3-4", so FFG exceedance potential appears
higher than surrounding areas. However, there is still a lot of
placement uncertainty among the available models, and some concern
that instability won't be sufficient to support multiple rounds of
heavy rain. While a SLGT risk is still possible with later
issuances, after coordination with WFO DLH opted to maintain the
MRGL risk at this time.

Weiss


Day 3
Valid 12Z Mon Aug 04 2025 - 12Z Tue Aug 05 2025

...THERE ARE MARGINAL RISK AREAS FOR THE NORTHERN ROCKIES, NORTHERN PLAINS/MINNESOTA, AND THE SOUTHEAST...

...Southeast...
Moisture streaming northeast ahead of the longwave trough axis will
maintain unsettled conditions and widespread showers/thunderstorms
from southern AL through GA and coastal SC. There is quite a bit of
uncertainty in the placement of the heaviest axis of QPF on D3
owing to uncertainty in accompanying mid-level impulses progged to
lift out of the Gulf on Monday, and this limits confidence from
upgrading the inherited MRGL risk to a SLGT risk at this time.
However, with PWs likely continuing at 2-2.25 inches overlapping
MUCAPE of more than 1000 J/kg, rainfall rates of 1-2"/hr or more
are likely within any convection that develops and then tracks
northeast. Some repeating rounds are possible, but SREF/GEFS/ECENS probabilities for 3"/24hrs are all quite modest at this time, and
the EC/EC-AIFS is north of the other guidance which could allow the
heaviest rain D3 to not overlap the heaviest rainfall footprint
from D1-2. For these reasons the MRGL risk was maintained and
adjusted, but a SLGT risk may be needed with later issuances.

...Northern Plains...
The closed mid-level low responsible for areas of heavy rainfall
Sunday will continue to lift northeast and weaken on Monday. The
weakening of this feature will result in less ascent, but a
lingering boundary in its wake could still produce enhanced low-
level convergence, primarily across Minnesota. The threat for
heavy rainfall appears lower D3 than D2, as both ascent and
thermodynamics are reduced, but locally rainfall rates in excess of
1"/hr are possible, with a secondary surge in convection possible
late in response to 850mb winds reaching 20-30 kts converging into
the region. With FFG likely to be lowered from antecedent rainfall
D1 and D2, isolated excessive rainfall impacts will again be
possible on Monday.

...Northern Rockies...
A shortwave moving northeast across ID/MT will help amplify a
trough shifting into the Northern High Plains on Monday. This will
drive enhanced ascent into the already broad synoptically forced
lift, helping to spawn a weak wave of low pressure tracking into
the High Plains the latter half of D3. Low-level southeasterly flow
will draw elevated PWs and MUCAPE into the region aiding a
moistening column from high-level SW flow emerging from the
Pacific. The result of this will likely be showers and
thunderstorms moving progressively eastward from the Northern
Rockies through the northern High Plains. With PW anomalies +1 to
+1.5 sigma above the climo mean, rainfall rates may reach 1"/hr at
times, which despite the anticipated progressive nature of these
cells, could produce isolated impacts due to runoff.

Weiss
$$
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FOUS30 KWBC 090755
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
355 AM EDT Sat Aug 9 2025

Day 2 Valid 12Z Sun Aug 10 2025 - 12Z Mon Aug 11 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FROM EASTERN
KANSAS NORTHEAST THROUGH SOUTHERN WISCONSIN...

...Central Plains through the Upper Midwest...
An extremely active pattern continues across the Plains and Upper
Midwest as the synoptic regime from D1 persists through the weekend.

An amplifying mid-level trough centered from ND through NM will
deepen to produce 500mb heights that may locally fall below the
10th percentile according to NAEFS. ALthough the primary vorticity
maxima in the core of the trough spins northeast into Ontario,
lingering impulses shedding back into the Four Corners maintain the
trough axis back to the west. This will persist mid-level SW flow
angling across the Central Plains and into the Upper Midwest, with
weak impulses rotating through the flow and persistent upper
diffluence within the RRQ of a poleward arcing jet streak
downstream of the primary trough axis providing deep layer ascent.
This pattern matches the conceptual model for a Maddox Frontal
rainfall event, and another day of heavy rainfall is likely Sunday
in portions of the region.

As the synoptic pattern stalls, a surface stationary front will
oscillate from WI through OK, providing a focus for convective
generation along the low-level convergent boundary. Additionally,
any weak impulse transiting the front could result in weak low-
pressure development along the boundary. This makes for a
challenging QPF and ERO forecast since the environment will be
extremely favorable for training heavy rainfall, but the exact
placement remains very much uncertain.

As far as the environment, thermodynamics are expected to be
exceptional for the area supporting intense rainfall rates. PWs
above 2", or well above the 90th percentile, are progged to surge
northward on return flow ahead of the front, combining with MUCAPE
of 2000 J/kg to fuel widespread convective development as the
850mb inflow/LLJ propagates northeast. Mean 0-6km winds will again
be parallel to the boundary, although with wind speeds are expected
to be generally more progressive than on Saturday, reaching 15-20
kts. However, bulk shear progged to reach 40 kts will support
organized cells, and Corfidi vectors collapsed to just 5 kts and
aligned against the mean wind indicate a high threat for
backbuilding cells leading to longer duration of heavy rainfall and
slow net cell motions. With rainfall rates of 2-3"/hr expected,
this could result in axes of 3-5 inches of rain with locally higher
amounts. This will likely result in scattered to numerous flash
flood instances, with locally significant impacts possible should
heavy rain train across urban areas.

There remains uncertainty into the placement of the heaviest
rainfall, and the inherited MDT risk was adjusted cosmetically for
the recent guidance to align both with the highest REFS/SREF
exceedance probabilities while also accounting for the expected
heavy rainfall footprint from D1. Additionally, some adjustments
were made to better reflect the CSU first guess field which pulled
the higher risk areas a bit SW from previous runs.

...Southwest...
A MRGL risk remains for portions of the Southwest on Sunday as
monsoonal moisture begins to return to the area leading to a more
active convective pattern. A mid-level trough extending down from
the Northern High Plains will continue to amplify Sunday, producing
lowered heights across the Four Corners and Desert Southwest,
through which weak spokes of vorticity will rotate. These lowered
heights and locally enhanced ascent will impinge into an
increasingly favorable thermodynamic environment to support
convection with heavy rainfall. Low-to-mid level flow will
gradually back more to the SW, allowing for a better draw northward
of PWs exceeding 1", which may spread as far north as the Mogollon
Rim and combine with MUCAPE of 500-1000 J/kg across the southern
half of AZ and NM. This will support scattered to widespread
showers and thunderstorms which will move slowly eastward through
the day. With rainfall rates as much as 1"/hr at times, this could
result in at least isolated instances of flash flooding, especially
across more vulnerable soils or terrain, and the MRGL risk was
maintained and adjusted for new guidance.

...Southeast...
Another very active day across portions of the Southeast is
expected as tropical moisture (PWs above 2.25 inches) persists in
response to a wave of low pressure drifting across the eastern
Gulf. The mid-level pattern remains quite diffuse into Sunday, with
a col sitting over much of the Southeast in response to broad
ridging along the Atlantic Seaboard. This suggests that features
will move little during the period, and guidance indicates a weak
shortwave drifting along the GA/SC coast once again on Sunday.

850mb inflow from the southeast will maintain impressive moist
advection onshore, and this wind, while modest at 15-20 kts, will
generally exceed the mean 0-6km winds which will be just 5-10 kts.
This will provide a two-pronged effect on the heavy rainfall threat
in that the 850mb wind exceeding the mean wind will drive large
scale enhanced ascent, while the weak mean winds will additionally
support slow movement of convection that develops. With rainfall
rates likely peaking at 2-3"/hr (30% chance for 2"/hr from the
HREF), maximum rainfall of 3-5" with locally higher amounts is
again possible on Sunday as reflected by SREF/GEFS/HREF/REFS
probabilities. Some of this may fall atop soils that are sensitive
from prior heavy rainfall on Friday and Saturday, leading to a
locally higher flash flood risk. The latest UFVS CSU First guess
field has a SLGT risk over coastal SC, which overlaps almost
identically with the SLGT risk on D1 and the highest REFS/HREF/GEFS probabilities into D2 (when available). For this reason a targeted
SLGT risk was again added, primarily for the SC coastal plain.

Weiss


Day 3 Valid 12Z Mon Aug 11 2025 - 12Z Tue Aug 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM NORTHERN
MISSOURI THROUGH NORTHERN ILLINOIS AND SOUTHERN WISCONSIN...

...Central Plains through the Great Lakes...
The amplifying trough across the High Plains and the accompanying
cold front producing the heavy rainfall across the Plains/Upper
Midwest Saturday and Sunday will gradually pivot eastward on D3
/Monday/. Despite this eastward translation, pinched 850-500mb flow
between this trough and a ridge to the east will maintain efficient
moist advection out of the Gulf, albeit with PW anomalies lower
than forecast for the weekend. This suggests that another day of
training convection is likely along the front from Oklahoma
through Michigan, but with somewhat reduced intensity. Rainfall
rates will likely still peak above 1"/hr at times, which through
training could produce 1-3 of rainfall (ECENS/GEFS probabilities
for 3+ inches below 10%), and where this rain overlaps with heavy
rain from the weekend (most likely on the western edge of the SLGT
risk area), scattered instances of flash flooding are possible.
Otherwise, any cells training along the front could produce
isolated responses and a broad MRGL risk draped along the length of
the front into the southern High Plains continues.

...Southeast...
Rinse and repeat for the Southeast, especially in the vicinity of
South Carolina, Georgia, and the Florida Panhandle, as onshore
return flow around an elongated high over the Atlantic spreads
tropical moisture onshore. PWs are again progged to be 2-2.25
inches with overlapping MUCAPE of 1000-2000 J/kg. Within these
impressive thermodynamics, forcing for ascent will be provided both
by land/sea convergence axes but also downstream of two
shortwaves: one moving near the SC coast and a second rotating
northward from the Gulf into the FL Panhandle. Both of these mid-
level features may reflect to the surface as inverted troughs,
providing additional convergence for slow moving thunderstorms
containing rainfall rates of 1-3"/hr. There is quite a bit of
spread among the global ensembles by D3 as to how far inland
convection will track, and as to whether there will be any focused
areas of heavier rainfall. For these reasons a broad MRGL risk
remains across the area for at least isolated flash flood
potential, especially since soils will be primed from heavy
rainfall anticipated on D1 and D2.

Weiss
$$
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FOUS30 KWBC 100835
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
435 AM EDT Sun Aug 10 2025

Day 2 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 THROUGH THE UPPER MIDWEST, AND THE COASTS OF THE CAROLINAS...

...Central Plains through the Great Lakes...
The anomalous trough drifting slowly eastward from the High Plains
will weaken slightly as heights rise across the Central Plains
Monday. This will have limited overall affect on the downstream
rainfall, however, as spokes of vorticity embedded within the flow
and the accompanying surface front remain in place to drive ascent,
with only slow eastward advance expected through D2.

Despite this eastward translation, pinched 850-500mb flow between
this trough and a ridge to the east will maintain efficient moist
advection out of the Gulf, albeit with PW anomalies lower than
forecast for the weekend (PWs around 1.75 inches or 0.5 to 1.0
standard deviations above the climo mean). This suggests that
another day of training convection is likely along the front from
Oklahoma through Michigan, but with somewhat reduced intensity from
prior days. Another challenges for D2 is the uncertainty in frontal
position and convective timing, as lingering boundaries from
Sunday's convection (with additional uncertainty in placement) will
play an important role into the training potential and heavy rain
axes on Monday. This suggests that despite a still favorable
synoptic pattern and elevated thermodynamics, the SLGT risk remains
the highest needed category for the D2 ERO.

On Monday, rainfall rates will likely still peak above 1"/hr at
times, which through training could produce 1-3 of rainfall
(ECENS/GEFS probabilities for 3+ inches below 10%), and where this
rain overlaps with heavy rain from the weekend (most likely on the
W/SW edge of the SLGT risk area), scattered instances of flash
flooding are possible. Otherwise, any cells training along the
front could produce isolated responses and a broad MRGL risk draped
along the length of the front into the southern High Plains continues.

...Southeast...
Yet another active day across the Southeast is expected Monday as
an inverted low-to-mid level trough drifts northeast along the
coast of the Carolinas. This trough will move within a favorable
thermodynamic environment characterized by still highly anomalous
PWs of 2 to 2.25 inches, although the slow retreat of the mid-level
ridge to the east should help ease some of this moisture the latter
half of D2. Still, the overlap of these elevated PWs with MUCAPE of
1000-2000 J/kg will support convection with heavy rainfall.

In general, convection across the Southeast on Monday should be
scattered in coverage, but some organization, or at least better
clustering, is likely in the vicinity of any shortwaves and the
inverted trough, primarily from the Grand Strand of SC to the
Crystal Coast of NC. Here, repeating rounds of convection with
efficient rain rates exceeding 2"/hr are likely, driven by
impressive low-level confluence. Elsewhere across the Southeast,
heavy rainfall rates are also likely, but with less organization,
but still slow storm motions. The rainfall probabilities for more
than 3" peak along the SC/NC coasts and the SLGT risk was adjusted
cosmetically for the new guidance. Otherwise, a broad MRGL risk
continues for slow moving thunderstorms across areas that have had
recent heavy rainfall, and an expansion was made into the Upstate
of SC where some of the high res CAMs suggest enough upslope to
enhance rainfall locally in that area.

Weiss


Day 3 Valid 12Z Tue Aug 12 2025 - 12Z Wed Aug 13 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE UPPER MIDWEST/GREAT LAKES, THE SOUTHWEST, AND GULF COAST/SOUTHEAST...

...Upper Midwest...
The anomalous mid-level trough that will produce the heavy rainfall
D1 and D2 across the Upper Midwest/Central Plains will weaken
Tuesday as shortwaves embedded within the trough become more
rapidly absorbed into westerlies across the northern tier of the
CONUS. A lingering shortwave trough, likely convectively enhanced,
pivoting across KS/MO will drive sufficient ascent for additional
rainfall along the weakening front, but with lesser moisture and
instability than was available earlier in the week. Still, at least
short term training of intense rainfall rates is likely as mean
layer winds align to the weakening front, which could result in
isolated instances of flash flooding.

...Southeast...
Elongated mid-level ridge extending westward from the Atlantic to
along much of the Gulf Coast will subtly retreat Tuesday as a
shortwave emerging from the Gulf lifts northward. The modest height
falls and PVA accompanying this feature will drive ascent into an
otherwise weakly forced environment, producing a favorable setup
for scattered to numerous thunderstorms from the central Gulf Coast
northeast along the periphery of the ridge into Georgia.
Thunderstorms that develop will contain heavy rainfall rates of
1-2"/hr in response to favorable thermodynamics characterized by
PWs of 2-2.25 inches overlapping MUCAPE as high as 2000 J/kg. The
general SW return flow will push storms along steadily to the N/NE,
but with repeating rounds possible and some organization beneath
the shortwave, a few instances of flash flooding could result as
rainfall reaches 2-3" in some areas.

...Southwest...
Mid-level ridging will expand but shift subtly westward on Tuesday
while weak impulses rotate around its periphery. This will help to
intensify instability across the region, and progs indicate a
larger plume of 1000 J/kg MUCAPE spreading across the southern
portions of AZ and NM, especially during peak aftn heating. This
will combine with PWs that will be above 1" in many areas south of
the Mogollon Rim, leading to a favorable environment for
convection. Where any of these impulses rotate aloft, enhanced
ascent will yield scattered to widespread thunderstorms with rain
rates approaching 1"/hr at times, and these storms will move
slowly/chaotically beneath the ridge. This could result in
isolated instances of flash flooding, most likely where any storms
track across more vulnerable terrain features or burn scars.

Weiss
$$
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FOUS30 KWBC 102016
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
416 PM EDT Sun Aug 10 2025

Day 2 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 THROUGH THE UPPER MIDWEST, THE COASTS OF THE
CAROLINAS, & THE FLORIDA PANHANDLE...

...Southern Plains & MO-KS-AR-OK...

The South Central U.S. will be sandwiched between two upper level
disturbances; one upper trough approaching from the Southern
Rockies, and mid-upper level trough axis over southern Texas. Atop
the atmosphere, modest diffluent 250mb flow will support divergence
aloft while a nearby surface frontal boundary acts as a trigger
for thunderstorms. Any residual outflow boundaries from Sunday
night's convection or from Monday afternoon's convection will also
likely play a role in firing off thunderstorms to the south and
east of the surface front. PWATs will generally be >1.8" along the
Red River and points north and east, while areas as far west as
the TX Panhandle and cap rock are between 1.4-1.6". In terms of
instability, lesser values (MLCAPE 500-1,000 J/kg) will be
available in the TX Panhandle, with greater over the MO-KS-AR-OK
region through Monday night. The 12Z HREF does show spotty areas of moderate-chance probabilities (40-60%) within the Slight Risk area
for >3" of rainfall, as well as low-chance probabilities (10-30%)
for >5" in central OK. Given these factors, the Slight Risk was
focused more here compared to the previous forecast cycle.

...Middle MS Valley...

The Slight Risk was scaled back here given the reduction in
available instability, latest QPF reduction, and lesser footprint
of >3" rainfall probabilities in the 12Z HREF. With soils growing
more saturated and the lingering presence of near 2" PWATs, there
is still a localized flash flood threat, hence the presence of a
rather large Marginal Risk area that stretches from the I-70
corridor from KS/MO on north through the Great Lakes.

...Florida Panhandle & Big Bend...

In coordination with TAE, introduced a Slight Risk for areas along
and south of I-10 in the FL Panhandle and Big Bend. As a mid-to-
upper level inverted trough axis approaches, it will be accompanied
by a wealth of anomalous PWATs that will approach 2.5" in some
areas. Modeled soundings show warm cloud layers just shy of
16,000ft deep in some cases with little-to-no capping inversions
Monday afternoon. On the eastern flank of the inverted trough,
925-850mb winds will be uniformly out of the SE. ECMWF soundings
over the Big Bend show Corfidi Upshear vectors that are <10 knots
Monday afternoon, suggesting the potential for back-building and
training thunderstorms. Given the abundance of tropical moisture
and MLCAPE up to 1,000 J/kg, it is quite possible to have
thunderstorms generate 2" of rainfall in as little as 30 minutes.
The scale of these storms are making QPF forecasts across CAMs
guidance widely varying on location, but the atmospheric parameters
support an increasingly concerning setup for flash flooding for Monday.

Mullinax

---Previous Discussion---

...Southeast...
Yet another active day across the Southeast is expected Monday as
an inverted low-to-mid level trough drifts northeast along the
coast of the Carolinas. This trough will move within a favorable
thermodynamic environment characterized by still highly anomalous
PWs of 2 to 2.25 inches, although the slow retreat of the mid-level
ridge to the east should help ease some of this moisture the latter
half of D2. Still, the overlap of these elevated PWs with MUCAPE of
1000-2000 J/kg will support convection with heavy rainfall.

In general, convection across the Southeast on Monday should be
scattered in coverage, but some organization, or at least better
clustering, is likely in the vicinity of any shortwaves and the
inverted trough, primarily from the Grand Strand of SC to the
Crystal Coast of NC. Here, repeating rounds of convection with
efficient rain rates exceeding 2"/hr are likely, driven by
impressive low-level confluence. Elsewhere across the Southeast,
heavy rainfall rates are also likely, but with less organization,
but still slow storm motions. The rainfall probabilities for more
than 3" peak along the SC/NC coasts and the SLGT risk was adjusted
cosmetically for the new guidance. Otherwise, a broad MRGL risk
continues for slow moving thunderstorms across areas that have had
recent heavy rainfall, and an expansion was made into the Upstate
of SC where some of the high res CAMs suggest enough upslope to
enhance rainfall locally in that area.

Weiss


Day 3 Valid 12Z Tue Aug 12 2025 - 12Z Wed Aug 13 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE UPPER MIDWEST/GREAT LAKES, THE SOUTHWEST, AND GULF COAST/SOUTHEAST...

2030Z Update...

There were some minor adjustments made this forecast cycle to the
Marginal Risk areas based on latest 12Z guidance and WPC QPF. The
Southeast will be closely monitored given the same feature
supporting a Slight Risk on Day 2 in the FL Panhandle and Big Bend
areas will move farther inland on Tuesday. However, there remains a
fair amount of spread regarding how much rainfall occurs and which
areas are favored. Given the lingering uncertainty, opted to
hold on to a Marginal Risk area with no upgrade this forecast cycle.

Mullinax

---Previous Discussion---

...Upper Midwest...
The anomalous mid-level trough that will produce the heavy rainfall
D1 and D2 across the Upper Midwest/Central Plains will weaken
Tuesday as shortwaves embedded within the trough become more
rapidly absorbed into westerlies across the northern tier of the
CONUS. A lingering shortwave trough, likely convectively enhanced,
pivoting across KS/MO will drive sufficient ascent for additional
rainfall along the weakening front, but with lesser moisture and
instability than was available earlier in the week. Still, at least
short term training of intense rainfall rates is likely as mean
layer winds align to the weakening front, which could result in
isolated instances of flash flooding.

...Southeast...
Elongated mid-level ridge extending westward from the Atlantic to
along much of the Gulf Coast will subtly retreat Tuesday as a
shortwave emerging from the Gulf lifts northward. The modest height
falls and PVA accompanying this feature will drive ascent into an
otherwise weakly forced environment, producing a favorable setup
for scattered to numerous thunderstorms from the central Gulf Coast
northeast along the periphery of the ridge into Georgia.
Thunderstorms that develop will contain heavy rainfall rates of
1-2"/hr in response to favorable thermodynamics characterized by
PWs of 2-2.25 inches overlapping MUCAPE as high as 2000 J/kg. The
general SW return flow will push storms along steadily to the N/NE,
but with repeating rounds possible and some organization beneath
the shortwave, a few instances of flash flooding could result as
rainfall reaches 2-3" in some areas.

...Southwest...
Mid-level ridging will expand but shift subtly westward on Tuesday
while weak impulses rotate around its periphery. This will help to
intensify instability across the region, and progs indicate a
larger plume of 1000 J/kg MUCAPE spreading across the southern
portions of AZ and NM, especially during peak aftn heating. This
will combine with PWs that will be above 1" in many areas south of
the Mogollon Rim, leading to a favorable environment for
convection. Where any of these impulses rotate aloft, enhanced
ascent will yield scattered to widespread thunderstorms with rain
rates approaching 1"/hr at times, and these storms will move
slowly/chaotically beneath the ridge. This could result in
isolated instances of flash flooding, most likely where any storms
track across more vulnerable terrain features or burn scars.

Weiss
$$
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FOUS30 KWBC 140754
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
354 AM EDT Thu Aug 14 2025

Day 2 Valid 12Z Fri Aug 15 2025 - 12Z Sat Aug 16 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
MINNESOTA AND WISCONSIN...

...Upper Mississippi Valley...
A cold front will progress slowly eastward Friday across Minnesota,
elongated from Wisconsin to South Dakota by the end of D2. This
front will elongate and pivot more to a W/E direction as the
driving mid-level flow gets squeezed between a trough over northern
Canada and a bulging ridge across the Lower/Mid Mississippi Valley.
As the flow becomes more zonal to align elongate the front, waves
of vorticity will surge eastward within the pinching flow to track
west to east along this front from the Dakotas into Wisconsin. This
will produce enhanced lift into an environment that will steadily
become more favorable for convection, and may feature extreme
thermodynamics of PWs above 1.75 inches overlapping MUCAPE of
3000-4000 J/kg later D2.

This suggests that thunderstorms will become scattered to
widespread, peaking later in the day as the LLJ ramps up to 25-35
kts from the SW. This will occur concurrently with a surge of bulk
shear to above 35 kts, and as warm cloud depths climb during this
period as well, convection will grow upscale, potentially into one
or more MCS, with rainfall rates of 1-3"/hr. Mean 0-6km winds of
15-25 kts suggest cells will move quickly eastward, but
redevelopment along the front and any upwind growth on MCS
boundaries could prolong this rainfall through
backbuilding/training. The inherited MRGL risk was modified
cosmetically and a targeted SLGT risk was added to match the
highest ensemble probabilities of 3 inches which also overlap some lower FFG.

...Mid-Atlantic through portions of the Southeast...
The cold front from Thursday will dissipate into a trough Friday
while pushing south towards AL/GA/SC. Despite the weakening of this
boundary and increasing heights aloft in the vicinity of an
expanding mid-level ridge, showers and thunderstorms are again
expected, although in a more scattered fashion than on Thursday.
PWs will remain elevated as tropical moisture continues across the
region, exceeding 2 inches in a ribbon from eastern NC through the
Gulf Coast of MS/LA. This will overlap with impressive MUCAPE above
2000 J/kg during peak heating to drive aftn convection, generally
of a pulse nature, across much of the region. Weak impulses are
modeled within the flow, but with minimal accompanying height falls
or PVA, so any organization will be tied to outflow boundaries or
storm mergers within the otherwise pulse environment. Despite
rainfall rates that will likely peak at 2-3"/hr thanks to the
robust thermodynamics, short lifespans and a lack of organization
suggests only a MRGL risk of excessive rainfall is needed.

...Southwest...
The flow across the Southwest on Friday becomes increasingly
pinched between an amplifying trough digging over California and a
bulging ridge centered near the Central Plains. Shortwave energy
and accompanying spokes of vorticity will periodically shed from
this upstream trough and track SW to NE from southern AZ through
the Four Corners, likely resulting in widespread convective
development, especially as a MUCAPE plume surges above 1000 J/kg.

It is possible that development will be slow to initiate on Friday
due to remnant overnight convection Thursday night leaving cloud
cover early, but most available models including the GFS-forced UA
WRF indicate widespread thunderstorms from southern AZ through
UT/CO and even into WY during the evening. Rainfall rates in
convection will likely peak above 1"/hr across AZ where
instability/PWs are higher, but should reach 0.5"-1"/hr elsewhere.
While 0-6km mean winds will be progressive enough to limit
individual cells from producing too much rain, sufficient bulk
shear of 20-30 kts, especially beneath any shortwave impulses, will
help organize convection into clusters to either lengthen rainfall
duration or result in repeating rounds of storms. Where this
occurs, rainfall probabilities above 1" reach as high as 30-40%,
and the MRGL risk was expanded northward from inherited.

...Western Gulf Coast...
Invest 98L and its accompanying potent mid- level circulation will
lift northwest into northern Mexico or southern Texas Friday
afternoon. To the east of this feature, accelerating low-to-mid
level winds will advect a plume of tropical moisture northward onto
the Texas coast, with PWs potentially exceeding 2.25 inches along
much of the Texas coast. While this is only around the 90th
percentile from the CFSR climatology, it will be accompanied by
MUCAPE exceeding 3000 J/kg drawn inland by 850mb winds of 20-30 kts
(equal to or greater than the mean 0-6km wind). Although the
deterministic models feature a wide variation in QPF output Friday,
and the resulting ensemble probabilities are suppressed in
response, it appears the setup is favorable for at least modest
inland penetration of training heavy rainfall within thunderstorms,
so a MRGL risk was added for portions of the region.

...Pacific Northwest...
The core of a rare August atmospheric river (AR) will move onshore
WA state on Friday, leading to prolonged heavy rainfall, continuing
from the landfall on Thursday and discussed in the D1 ERD. While
QPF will likely be greater on Friday (potentially 2-4" and even
locally greater in the higher terrain of the Olympics and northern
Cascades), the threat for excessive rainfall remains somewhat
uncertain. Impressive PWs of 1.25 to 1.5 inches (locally the
highest ever recorded in the 5-week CFSR climatology from NAEFS)
and formidable 850mb winds will help drive strong upslope ascent
supporting this intense rainfall into upwind terrain features.
While it is nearly certain rainfall will be heavy, there is less
certainty into whether rain rates can be sufficient to cause rapid
runoff atop very dry soils since MUCAPE is forecast to be
negligible which should keep rain rates to around 0.5"/hr. If this
rain were to fall atop recent and sensitive burn scars, instances
of flash flooding could result, but at this time the threat appears
to be below 5% when considering the climatology of the event as
well. After coordination with WFO SEW and OTX, other than some
concern about a few sensitive burn scars, agreement was made on
keeping a MRGL risk out of the forecast at this time.

Weiss


Day 3 Valid 12Z Sat Aug 16 2025 - 12Z Sun Aug 17 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE UPPER
MIDWEST INTO THE GREAT LAKES...

...Central Plains through the Great Lakes...
Pinched mid-level flow will become increasingly squeezed between a
trough over Ontario and a ridge expanding from the Gulf Coast.
Between these two features, nearly zonal flow will force a cold
front to generally align west to east and stall, providing a
convergent impetus for convection. Along this front, spokes of
vorticity will track west to east leading to locally enhanced
ascent to support waves of low pressure, while 850mb inflow returns
around the high pressure ridge and reaches 25-35 kts to draw
elevated thermodynamics characterized by PWs above 1.75 inches and
MUCAPE of 4000 J/kg into the boundary. This will support multiple
rounds of thunderstorms through the day, peaking during the
evening/Saturday night, with rainfall rates of 1-2"/hr or more at
times, leading to scattered instances of flash flooding. A SLGT
risk has been added for portions of this area where probabilities
from the SREF/GEFS/ECENS align for more than 3" of rain.

...Southwest...
Continued S/SW mid-level flow around the periphery of a ridge
positioned over the Mississippi River Valley will maintain elevated
moisture into the Southwest on Saturday. Guidance continues to
suggest that weak shortwaves/vorticity maxima will lift northeast
embedded within the flow, although the intensity of these features
is generally modest, and weaker than on Friday. Additionally,
although 850mb flow will remain southerly over NM, it is progged to
shift a bit more to the west over AZ, lowering the overall PW
anomalies and indicating the greater risk for any isolated flash
flooding will shift east from prior days. MUCAPE of 500-1000 J/kg
will support rainfall rates that may approach 1"/hr at times, and
if these fall across more sensitive features like burn scars or
urban areas, isolated instances of flash flooding could result.

...Southeast...
A wave of low pressure along a weakening cold front will drift
southeast away from the NC coast on Saturday. At the same time, a
building ridge over the Mississippi River Valley will lead to
anti-cyclonic mid-level flow out of the NW into the Southeast,
setting up a situation with moist confluent flow intensifying over
the region. PWs will likely remain elevated above 2" along the Gulf
Coast, but be lower elsewhere as drier air tries to advect from the
NE around the offshore low, and this will result in less widespread
coverage of thunderstorms than prior days. While coverage of
convection is expected to generally be scattered, some locally
enhanced rainfall along any convergence axes is possible due to
rainfall rates that will still reach 1-2"/hr at times. Where these
fall across vulnerable soils from widespread convection on prior
days, impacts could result, and a MRGL risk continues for portions of the area.

Weiss
$$
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