FOUS30 KWBC 270750
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
350 AM EDT Mon Apr 27 2026

Day 1
Valid 12Z Mon Apr 27 2026 - 12Z Tue Apr 28 2026

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

Multiple rounds of convection are expected today ahead of a cold
front extending from an anomalously deep spring low. Significant
northward moisture transport will result in a plume of PWs above 1
inch as far north as Lake Superior, and above 1.5 inches as far
north as Chicago. Along the entire length of the cold front, these
values will generally approach the 99th percentile for late April
and, combined with moderate to strong instability, should support
hourly rain rates in the 1 to 2 inch range. A limiting factor for
flash flooding will be the dominant convective mode -- very likely
to be relatively narrow squall lines, forced by a steadily
advancing cold front, that will limit the overall duration of the
heavy rain rates.

However, an area from northern and central Missouri, into much of
Illinois and Indiana, will have a greater potential for training
convection. This will be due to a significant upstream complex of
thunderstorms over northeast Kansas as of 07Z, which should shift
east over the remainder of the morning. The orientation of the
convective line is closer to parallel with the deep layer shear
vector, which will favor training over northern Missouri at the
start of the period. Eventually, this activity may produce an
outflow boundary oriented in a west-east fashion that would focus
subsequent convective development in a more favorable configuration
for additional training. The broad Slight Risk was maintained and
adjusted to better fit the latest guidance where probabilities of 1
inch per hour rain rates are highest.

Further south, a Marginal Risk was extended from Arkansas and
Tennessee southwest into central Texas to account for a conditional
threat of localized heavy rainfall and flash flooding. The
environment in these areas will be characterized by strong
instability (CAPE in excess of 3000 j/kg) and abundant deep
moisture (PW between 1.5 and 1.8 inches). The QPF signal in
guidance is inconsistent, but enough to indicate a threat for
isolated to scattered thunderstorms, primarily in the afternoon and
evening. The combination of the aforementioned instability with
strong deep layer shear could lead to a few slow-moving
supercells, which has been a theme in recent days. It is a classic
conditional threat -- while much of this region further south along
the front could remain dry, any storms that become organized and
rooted in the very unstable boundary layer could produce localized
very heavy rainfall.

Lamers


Day 2
Valid 12Z Tue Apr 28 2026 - 12Z Wed Apr 29 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM THE ARKLATEX
INTO THE MID SOUTH...

A favorable environment will exist for numerous organized
thunderstorms over the southern U.S. on Tuesday, with a broad warm
sector containing very strong instability (CAPE over 3000 j/kg),
deep moisture (PW climbing into the 1.6 to 2.0 inch range), and
strong deep layer shear (0-6km bulk shear 40-60 knots). In that
sort of environment, rain rates should reach 2 inches per hour. The
open question is what sort of mesoscale boundaries may exist to
focus convective development, and whether or not some of these will
be oriented in a west-east fashion (parallel to the bulk shear
vectors). Any prominent boundaries that are favorably oriented
could easily focus a corridor of significant rainfall and flash
flooding in this sort of environment. However, an equally plausible
scenario would be more scattered clusters and lines of
thunderstorms that can produce localized heavy rainfall and flash
flooding, but fail to focus the convection in a way that leads to
more significant totals. For now, it seems reasonable to maintain
the broad Slight Risk and wait for greater confidence in the
mesoscale details.

Lamers


Day 3
Valid 12Z Wed Apr 29 2026 - 12Z Thu Apr 30 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM CENTRAL AND
SOUTHEAST TEXAS TO THE CENTRAL GULF COAST...

The threat of excessive rainfall and flash flooding seems to be
increasing in the most recent set of model guidance, due to a
continuation of strong instability and the arrival of a plume of
unusual amounts of mid-level moisture. Backward trajectory
analysis indicates that moisture around 3km above the surface
originated in the tropical central Pacific, advected into the
southern U.S. by an anomalously strong subtropical jet (300mb winds
around 60+ knots) extending about 6000 mi. from the Marshall
Islands, to just south of Hawaii, all the way to Texas. This should
push PW values over the whole region above 1.7 inches, and above 2
inches in portions of Texas, which is quite unusual. For instance,
a 2+ inch PW has only been observed on an upper air sounding at
Corpus Christi 3 times prior to May 1st (36 year period of record;
since 1990). Although model QPF is not exceptionally high at this
point, that may largely be a function of a lack of high-res
guidance from convection-allowing models. The environment (when
also considering strong bulk shear to around 50 knots) would favor
organized thunderstorms with very high rain rates, potentially in
excess of 2 inches per hour. Given that the previous outlook had
probabilities below 5 percent, the main change with this update is
to introduce a Marginal Risk, but a further upgrade may be
required, especially across parts of Texas.

Lamers
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 280808
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
408 AM EDT Tue Apr 28 2026

Day 1
Valid 12Z Tue Apr 28 2026 - 12Z Wed Apr 29 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM THE ARKLATEX
REGION INTO THE MID SOUTH...

A favorable environment will exist for numerous organized
thunderstorms over the southern U.S. today and tonight. Outflow
from steadily advancing squall lines over the Tennessee Valley
should provide a more distinct focus for renewed convective
development over the forecast period. The boundary is likely to be
oriented west-east, essentially parallel to 40-50 knot bulk shear
vectors. Although the air mass north of the boundary may modify
with time, it should still provide low-level convergence and a
contrast in instability. South of the boundary, the warm sector
will have very strong instability (CAPE over 3000 j/kg) and deep
moisture (PW approaching 2 inches; above the 99th percentile for
late April). This parameter space is very supportive of high rain
rates, potentially in excess of 2 inches per hour in the most
intense and organized thunderstorms.

If anything, recent hi-res model runs (06Z HRRR, 00Z RRFS in
particular) have focused the heavy rainfall signal even more into a
corridor approximately 100 miles wide, with 2-4 inch totals and
localized maxima even higher. This is consistent with the expected
pattern described above, with repeated rounds of thunderstorms
along a distinct mesoscale boundary. The main change with this
outlook was to narrow the Slight Risk a bit, especially by trimming
from the stable (northern) periphery well into the stable side of
the mesoscale boundary. It could potentially be focused a bit more,
and that will be a consideration later today. A mitigating factor
for flash flood impacts could be the severe to extreme drought
conditions in place across much of the Slight Risk area. With rain
rates potentially in excess of 2 inches per hour, and heavy rain
sustained for several hours in some cases, drought conditions may
not necessarily prevent impacts but could lead to more isolated
instances of flash flooding. This is still consistent with the
Slight Risk definition. Flash flood guidance factors in current
ground and streamflow conditions, and HREF and REFS probabilities
still show about a 15-30 percent chance of exceeding FFG despite
the overall dry antecedent setup.

Lamers


Day 2
Valid 12Z Wed Apr 29 2026 - 12Z Thu Apr 30 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM CENTRAL AND
SOUTHEAST TEXAS TO THE CENTRAL GULF COAST...

The outlook for Day 2 has remained mostly unchanged, with a
Marginal Risk in a corridor from Texas through Alabama along the
western and central Gulf Coast. A threat of excessive rainfall and
flash flooding is expected, due to a continuation of strong
instability, and the arrival of a plume of unusual amounts of mid-
level moisture. Backward trajectory analysis indicates moisture
around 3km above the surface can be traced along an anomalously
strong subtropical jet extending back into the tropical central
Pacific Ocean. This should push PW values over the risk area above
1.7 inches, and above 2 inches in portions of Texas, which is quite
unusual for April. Given this, it's possible an upgrade to Slight
Risk may be needed in future outlook updates. However, hi-res
guidance is just coming into view. While the extended HRRR and RRFS
do both show rain rates in this environment reaching (and even
exceeding, in some cases) 2 inches per hour, confidence is not high
on placement of greater concentrations of convection. Additionally,
there doesn't seem to be much signal for backbuilding and training,
except perhaps via cell mergers, which could lead to more limited
duration of heavy rain. Therefore, the risk level was held at
Marginal for now for the entire region.

Lamers


Day 3
Valid 12Z Thu Apr 30 2026 - 12Z Fri May 01 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN CENTRAL TEXAS...

Increasing mid-upper level height falls over New Mexico and Texas,
due to a strong shortwave pushing through northern Mexico, should
lead to a low-level mass field response with increasing south to
southeast inflow across southern and central Texas. That will also
lead to a gradual uptick in low-level convergence between the
developing low-level jet, and an easterly cool conveyor belt to
the north, in a more stable region from Oklahoma into northwest
Texas. The result should be more numerous thunderstorms over the
course of the Day 3 period, particularly by Thursday Night. Deep
moisture will remain firmly in place, although the instability
should shift to a narrower CAPE profile with lower equilibrium
levels. That trend, in combination with PWs of 1.5 to 1.8 inches,
should support increasingly efficient, warm rain processes in
convective bands.

Furthermore, some training of the lower-topped convective bands may
occur. With stronger instability over South Texas, the Rio Grande
Valley, and far northeast Mexico, and steadily increasing forcing
from the approaching wave upstream, persistent new convective
growth upstream of convective bands is plausible.

Putting all these factors together, a Slight Risk was introduced
over Central Texas. This was placed where drought conditions either
do not exist or are much lower on the scale; that also happens to
be where some ensemble QPF signal is strongest. It's possible the
Slight Risk may trend southeast with time as AI guidance is
positioned on the southeast flank of the guidance envelope, and
would seem to be a logical corrective to the usual bias of QPF
maxima placed too far in the direction of a stable air mass,
especially with 2-3 days of lead time.

Lamers
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 010838
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
438 AM EDT Fri May 1 2026

Day 1
Valid 12Z Fri May 01 2026 - 12Z Sat May 02 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN CENTRAL AND
SOUTHEAST TEXAS EASTWARD ALONG THE CENTRAL GULF COAST...

Once again...minor reshaping of the Marginal and Slight Risk areas
were made to reflect small adjustments made in the WPC
deterministic QPF and the suite of 01/00Z global and CAM guidance. The
axis of the heaviest rainfall still forecast to span from eastern
Texas to eastern Louisiana and southern Mississippi where the best
moisture convergence and instability will be present. Recent rains
across the western an central Gulf states have increased soil
saturation, lessening the amount of additional rainfall required
for areas of flash flooding. Hourly rates of 1 to 3 inches/hr to
streak from eastern Texas to eastern Louisiana.

The overall evolution aloft coupled with a broad axis of
formidable moisture anomalies and instability should lead to an
axis of heavy rainfall across the Southern Plains from Texas over
through the Lower Mississippi Valley today into early Saturday
morning. A quasi-stationary front will orient itself across south-
central TX down to around the Gulf coast as a wave of low pressure
rides along the boundary. With precipitable water values forecast
to be 1.7 inches to 2.1 inches (in the 95th percentile or higher
for this time of year)...efficient warm rain processes can result
in torrential downpours with resulting flash flooding especially in
light of the upper divergence tied to the mid- and upper level
wave making its way through the southern Great Basin early this
morning. Thus there is little overall change to the forecast
reasoning for a high-end Slight risk area from parts of Texas into
Louisiana embedded within the broader Slight Risk area.

Farther east...the Slight risk area tapers off into a Marginal Risk
area where rainfall rates and amounts still have the potential to
result in flash flooding but where ingredients are not as well
aligned. The question in dry/drought areas always comes down to
rates and resulting amounts (whether it is from training or repeat
rounds). Thinking here rates may not be enough alone (with PW's
generally < 1.75-ish) but some potential for training prior to
frontal passage. The 01/00Z HREF neighborhood probs for 1-hr amts
at 1 in and 2 in thresholds focused generally along the LA/MS coast
(admittedly sub SLGT). The RRFS..which has a tendency to be
overconfident with probs and overly expansive...seemed to show its
bias on its 30/18Z run but focused pretty much along the same axis.
There remained some question on the latitude of the
axis...considering the latest UFVS verified machine learning
guidance focused a bit north of the HREF/RRFS axis closer to the
support offered by an upper jet streak.

Bann


Day 2
Valid 12Z Sat May 02 2026 - 12Z Sun May 03 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE SOUTHEAST U.S....

A progressive upper trough is expected to help focus and sustain
showers and thunderstorms across portions of the Southeast United
States on Saturday into the early morning hours of Sunday. More importantly...the trough should result in any convection moving
with minimal risk of back-building or training. The setup promotes
a relatively favorable environment suitable for heavy rainfall
with the stronger cell cores capable of producing rainfall rates
between 1-2"/hr in a region where Flash Flood Guidance values
remain high. There was enough of a signal for the possibility of
some urban flooding to warrant keeping a previously-issued Marginal
Risk in place with minimal amount of changes needed.

Bann


Day 3
Valid 12Z Sun May 03 2026 - 12Z Mon May 04 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THEm SOUTHEAST FLORIDA PENINSULA ON SUNDAY...

A cold front associated with an area of low moving northeastward
off the eastern US seaboard will be draped across the central
portion of the Florida peninsula on Sunday...with the front
separating an airmass with precipitable water values at or
somewhat less than 0.5 inches in the panhandle and adjacent
portions of the peninsula to values in the 1.75 inch to 2.00 inch
over the southern half of the peninsula for much of Sunday and
Sunday evening. Mid- and upper-level shortwave energy embedded
within fast flow aloft will help focus and sustain thunderstorms
that could produce 1.5 to 2.5 inch per hour along and south of the
boundary. There remained enough of a signal for the potential of
some urban flooding across the larger urban areas so opted to keep
with the Marginal Risk area due to the high flash flood guidance.
Even if the QPF remains similar in future cycles...where/how much
rain falls in Days 1 and 2 will affect the flash flood guidance as
Day 3 makes its way towards becoming a Day 1 outlook.
Regardless...downpours and localized multiple-inch rainfall amounts
in the major cities is more likely to have flood- related problems
in either scenario.

Bann
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 030825
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
425 AM EDT Sun May 3 2026

Day 1
Valid 12Z Sun May 03 2026 - 12Z Mon May 04 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHEAST FLORIDA PENINSULA...

Just enough of a signal in the 03/00Z CAMS to maintain the Marginal
Risk area. The focus will be over the urban southeast coast as a
front advances into a region of deeper moisture and where CAPE
tends to be under 1000 J per kg. The 03/00Z HREF does depict a
low-end neighborhood probability of FFGs being exceeded over the
southern tip of the Florida peninsula in the 03/21Z to 04/00Z
period but the stronger signals in the guidance is for heavier
rainfall to be hugging the coast or remaining just off-shore. It
was noted that over the past couple of days...numerical models have
been cutting back the amount of moisture in the lowest layers which

Bann


Day 2
Valid 12Z Mon May 04 2026 - 12Z Tue May 05 2026

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Bann


Day 3
Valid 12Z Tue May 05 2026 - 12Z Wed May 06 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE MID MISSISSIPPI VALLEY INTO THE OHIO VALLEY...

Deep layer southwesterly flow leading into the start of the period
will be drawing moisture into parts of the Plains and then
downstream toward the Great Lakes and the Ohio Valley. As a trough
amplifies over the central part of North America and a jet streak
forms over the Southwest US and approaches the Plains...the chance
for showers and thunderstorms increases along and ahead of a
develops surface front. With precipitable water values of 1.75 to
1.9 inches embedded within a broader 1.5 to 1.75 area...which was
pushing two standardized anomalies greater than climatology for
this time of year--locally heavy rainfall and the associated risk
of localized flooding from late Tuesday afternoon into early
Wednesday is possible.

Bann
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 040826
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
426 AM EDT Mon May 4 2026

Day 1
Valid 12Z Mon May 04 2026 - 12Z Tue May 05 2026

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Bann


Day 2
Valid 12Z Tue May 05 2026 - 12Z Wed May 06 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE MID MISSISSIPPI VALLEY INTO THE OHIO VALLEY...

Deep layer southwesterly flow leading into the start of the period
will be drawing moisture into parts of the Plains and then=20
downstream toward the Great Lakes and the Ohio Valley. That large=20
scale picture has changed little but subtle run to run difference=20
in the global models and convective allowing models continues to=20
result in minor adjustments to the ERO. A mid- and upper-level=20
trough will be amplifying over the central part of North America=20
and a jet streak forms over the Southwest US and approaches the=20
Plains...the chance for showers and thunderstorms increases along=20
and ahead of a develops surface front. With precipitable water=20
values of 1.75 to 1.9 inches embedded within a broader where=20
precipitable water values of 1.5 to 1.75 are going to be more=20
common...areal average rainfall is expected to be on the order of 1
to 1.25 inches. In general this will be beneficial rain. However=20
there may be isolated areas where rain rates lead to local flash=20
flooding. There was spread between model members with the ARW core
favoring a western solution while models with an NMM core favored
areas farther east. Given the synoptic pattern and with the support
of the global models...the ERO was kept in general along and east
of the Mississippi River.

Bann


Day 3
Valid 12Z Wed May 06 2026 - 12Z Thu May 07 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE INTERIOR SOUTHEAST UNITED STATES...

Maintained a Slight Risk of excessive rainfall introduced by the
WPC Medium Range desk as shortwave energy drops out of Canada and
across much of the central and eastern United States. The coverage
and rainfall intensity should be increasing on Wednesday as the
best dynamics and the best Gulf moisture coverage with a frontal
boundary over the interior portion of the Southeast US.=20
Deterministic QPF tends to cluster in the 1.5 to 3 inch amounts=20
across part of the Tennessee Valley into the southern Appalachians
from Wednesday into early Thursday due to the presence of surface=20
dewpoints close to 70 degrees getting drawn northward from the=20
Gulf. Whether or not the convection evolves into line will affect=20
the amount of rainfall and any associated risk of flash flooding.

Bann
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 050827
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
427 AM EDT Tue May 5 2026

Day 1
Valid 12Z Tue May 05 2026 - 12Z Wed May 06 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE MID MISSISSIPPI VALLEY INTO THE OHIO VALLEY...

Deep layer southwesterly flow had drawn Gulf moisture into parts
of the Plains and then downstream toward the Great Lakes and the
Ohio Valley. The resulting showers and thunderstorms today will be
able to tap into an atmosphere that generally has 1.5 inch
precipitable water or greater extending as far north as Ohio by the
overnight hours. The southeastward adjustment of the Marginal Risk
area still looks good and spans the placement of the 2 inch
contour shown by a handful of ARW-core and NMM-core ensemble
members. So few changes were needed and were not made due to a
fundamental shift in forecast reasoning.

Bann


Day 2
Valid 12Z Wed May 06 2026 - 12Z Thu May 07 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE INTERIOR SOUTHEAST UNITED STATES...

Maintained the slight southward shift of the previously issued Slight
Risk area introduced a couple of days ago. The coverage and
rainfall intensity should be increasing on Wednesday as a large
scale trough over the northern Plains continues to amplify and
result in a 140 kt to 160 kt upper level jet over the Tennessee
Valley during the latter part of the period. The resulting upper
divergence, steepening mid-level lapse rates and increasing
moisture and instability should result in convection capable of
producing heavy rainfall rates and embedded areas of rainfall
amounts of 3 to 5 inches as suggested by the latest run of the
RRFS. There is a fairly wide spread in the north/south placement of
that heavier axis. As a result...the Slight area was expanded
somewhat and tended to cover the greatest overlap of higher QPF and
exceedance probabilities. Thinking is that there are some
probabilities supportive of a higher-end slight risk embedded
within the broader Slight. The continued amplification of the upper
trough should keep the convection moving southward with time
during the overnight hours.

Bann


Day 3
Valid 12Z Thu May 07 2026 - 12Z Fri May 08 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE GULF COAST REGION TO THE SOUTHEASTERN UNITED STATES...

Showers and thunderstorms along and ahead of a surface cold front
will be lingering into Thursday from parts of the Gulf coast region northeastward into parts of Georgia and South Carolina. At this point...rainfall rates look to be decreasing as the better upper
level dynamics pull off to the northeast and low level flow becomes
directed along...rather than normal...to the front. Maintained a
Marginal Risk area where there could be overlap with areas somewhat
higher soil moisture content from recent rainfall. Overall the
rainfall looks to be more beneficial than not.

Bann
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 101800
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
200 PM EDT Sun May 10 2026

Day 1
Valid 16Z Sun May 10 2026 - 12Z Mon May 11 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
CENTRAL AND NORTH TEXAS...

...16Z Update...

The Slight Risk area was expanded a bit with this update, mostly
towards the south but also to include the rest of the DFW
Metroplex. Clusters of storms are expected to develop this
afternoon, likely as a continuation of the showers and storms
ongoing currently over Oklahoma, but developing further south into
Texas. Much of the convective activity is expected to congeal south
and west of the Metroplex, but urban concerns and some expected
development over the Metroplex still heighten the flash flooding
risk into the lower-end Slight category. Meanwhile, while
convection will be more numerous and strong further south and west,
less urban development may help to mitigate the flash flooding
threat a bit. By late evening, around 03Z/10pm CDT or so, the
convection is expected to have organized into a mostly single line
of storms that will progressively shift southeast towards the Gulf.
This should greatly mitigate the flash flooding threat by that
point and beyond. Thus, the flash flooding threat is greatest in
the late afternoon and evening while the storms are still
organizing and therefore have more chaotic and slow forward motions.

Wegman

...Previous Discussion...

The overall forecast philosophy for the new Day 1 period remains
largely consistent with the previous thinking, though an upgrade to
a Slight Risk has been introduced for portions of Central and
North Texas. While some uncertainty remains regarding the exact
evolution of the convective elements, a growing signal for higher-
end rainfall totals is becoming evident in the latest guidance.

Totals of 2-4 inches are increasingly likely across portions of
Central and North Texas by the late afternoon and evening,
supported by a moist, unstable airmass and strong ascent. Deepening
moisture is expected to pool along a composite surface boundary,
with PWs climbing to around 1.5 inches near the intersection of the
cold front and dryline. This moisture is expected to interact with
strong low level convergence and increasing upper level divergence
as a shortwave trough moves east, generating numerous storms
capable of producing heavy rainfall rates.

Further raising the concern for heavy amounts and potential flash
flooding will be cell training. Storms developing along the
boundary and ahead of the approaching wave may track over some
areas repeatedly, leading to localized excessive totals. Both the
HREF and RRFS indicate the potential for this setup, showing their
highest probabilities for QPF exceeding 2 inches extending from
parts of Central into North Texas, including southern sections of
the DFW Metro. Therefore, the Slight Risk was introduced to reflect
increasing confidence for scattered flash floods within this area.

Elsewhere, the Marginal Risk was expanded a bit, but remains
centered across much of the same region, reflecting the potential
for convective storms and heavy rainfall rates, though with less
organization or lower confidence in the potential for heavy
accumulations in comparison to the upgraded Slight Risk area.

Pereira


Day 2
Valid 12Z Mon May 11 2026 - 12Z Tue May 12 2026

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

...18Z Update...

A Marginal Risk of excessive rainfall was introduced for the
central Gulf Coast with this update. A strong cold front pushing
south out of the interior U.S. will interact with still sufficient
Gulf moisture (PWATs between 1.5 and 1.75 inches) along the coast
to force a renewed round of convection ahead of the front, which
may also interact with the sea breeze. Corfidi vectors suggest
storm movement will be fast towards the east, so backbuilding
potential appears low. However, this area was hard-hit with heavy
rain totaling over 3 inches in several areas of southeast
Louisiana, with totals up to 2 inches across much of the rest of
the Marginal Risk area just yesterday. Thus, while the area will be
recovering today through tomorrow morning, expect that any heavy
rainfall of meaningful duration may still lead to an instance of
flash flooding or 2, especially in the urban areas within the
Marginal Risk.

Wegman


Day 3
Valid 12Z Tue May 12 2026 - 12Z Wed May 13 2026

The probability of rainfall exceeding flash flood guidance is less
than five percent.

Wegman
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 110808
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
408 AM EDT Mon May 11 2026

Day 1
Valid 12Z Mon May 11 2026 - 12Z Tue May 12 2026

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

Renewed convection expected along the Gulf coast as a strong cold
front pushes south into the Gulf. Sea breeze and pooling PW values
of 1.5 to 2.0 inches will help enhance rainfall along the central
Gulf Coast. Recent rainfall has increased soil saturation for
parts of the region which in turn reduces the amounts needed for
isolated instances of flash flooding. The latest guidance has areal
averages of 1 to 3 inches with very local maximums of 4+ inches.
The environment will be conducive for progressive storm motion
which may limit the threat for flooding problems, however isolated
flash flooding with be possible especially over sensitive soils. A
Marginal Risk remains in effect from eastern Texas to the Florida
Panhandle.

Campbell


Day 2
Valid 12Z Tue May 12 2026 - 12Z Wed May 13 2026

The probability of rainfall exceeding flash flood guidance is less
than five percent.

Campbell


Day 3
Valid 12Z Wed May 13 2026 - 12Z Thu May 14 2026

The probability of rainfall exceeding flash flood guidance is less
than five percent.

Campbell
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 120811
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
411 AM EDT Tue May 12 2026

Day 1
Valid 12Z Tue May 12 2026 - 12Z Wed May 13 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR ALONG THE
I-95 CORRIDOR IN FLORIDA...

Heavy rainfall possible along the eastern coast of Florida during
this period as a cold front advances southward through the state.
Onshore flow along with pooled PW values in excess of 1.75 inches
will help fuel enhanced rainfall initially. Diurnal seabreeze=20
effects will interact further with the cold front, with a=20
convergence axis expected along the east coast of Florida.
HREF neighborhood probabilities suggest a high likelihood (over=20
90%) of QPF exceeding 3 inches, and a moderate chance (around=20
60-80%) over the urban center of Jacksonville. Due to ongoing=20
drought conditions, most of the rainfall will be beneficial which=20
will result in a low-end marginal threat for much of the eastern=20
coastline of Florida.

Campbell


Day 2
Valid 12Z Thu May 14 2026 - 12Z Fri May 15 2026

The probability of rainfall exceeding flash flood guidance is less
than five percent.

Campbell


Day 3
Valid 12Z Thu May 14 2026 - 12Z Fri May 15 2026

The probability of rainfall exceeding flash flood guidance is less
than five percent.

Campbell
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 190745
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
345 AM EDT Tue May 19 2026

Day 1
Valid 12Z Tue May 19 2026 - 12Z Wed May 20 2026

...THERE ARE SLIGHT RISKS FOR EXCESSIVE RAINFALL FOR PORTIONS OF=20
TEXAS AS WELL AS FOR SOUTHERN ILLINOIS AND INDIANA...

...Texas...

A line of intense showers and thunderstorms currently expanding=20
south across northern and western Oklahoma will continue south and
east through the early morning into northeast Texas. With peak
solar heating around midday, the line of storms will encounter an
increasingly unstable, and increasingly moist air mass situated
across much of Texas. Guidance suggests that several lines of
storms will develop in north Texas through the early afternoon.
Cold pools and lift ahead of the lines should allow individual
cells to develop out ahead of the lines, which will locally
increase the duration of heavy rains in those areas hit by first
the cells, and then the line shortly thereafter. This could cause
local flash flooding, especially should that occur over the
Metroplex or other urban areas in north Texas. By mid to late
afternoon, upper level energy may support areas of convection
across central and south Texas that will be separate from any lines
to the north. Mergers with the lines as they press south across the
state and any individual cell mergers within the clusters of storms
may also pose a localized flash flooding threat. By evening, the
storms will continue pushing into south Texas, potentially
impacting the San Antonio and Houston metros before they push into
the Gulf and deep south Texas through the predawn hours.

Overall the above-described scenario should keep flash flooding
instances mostly to localized, widely scattered occasions. However,
since the storms will cover much of the state, it's probable that
in flood prone areas, the flash flooding threat could be greater. Unsurprisingly with so many clusters of storms expected, the CAMs
are not having a great handle on them, so the Slight was expanded
to cover the Texas Triangle. Despite the antecedent dry soil
conditions over most of the state, PWATs will likely exceed 2
inches along the Gulf Coast for when the storms reach there
tonight. Thus, any and all storms will be capable of heavy rainfall
rates that could cause flash flooding.

...Southern Illinois and Indiana...

After rounds of showers and storms caused flash flooding in
portions of Illinois and Indiana yesterday, the soils in the area
are generally saturated due to widespread multiple-inch totals from yesterday/Monday. Much of the day today will be dry. Towards=20
evening however, renewed rounds of showers and thunderstorms will=20
develop with the approach of a strong cold front, significant=20
moisture and instability advection ahead of the front, and upper=20
level disturbances helping add to the overall environmental=20
forcing. Thus, overnight, expect multiple rounds of training
showers and thunderstorms tracking up the Ohio River Valley. With a
robust LLJ supporting the storms, they should have no trouble
maintaining their organization despite the lack of solar heating.
Since the soils are fully saturated, most, if not all the rainfall
will convert to runoff. Thus, the inherited Slight Risk was
expanded southwest to include much of southern Illinois with this
update.

Wegman


Day 2
Valid 12Z Wed May 20 2026 - 12Z Thu May 21 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE EDWARDS
PLATEAU REGION OF SOUTHWEST TEXAS...

A developing low level jet of deep Gulf moisture will advect
northwestward up the Rio Grande in south and southwest Texas in
response to height falls and an approaching shortwave moving
towards that area from Mexico. Numerous showers and thunderstorms
will develop late afternoon across the Edwards Plateau as a dry
line pushes east from the Big Bend area. The storms feeding off
PWATs of 1-1.5 inches, which is 2-2.5 sigma above normal for this
time of year in that part of the country are expected to become
plenty capable of producing heavy rain in an otherwise dry part of
the country. More susceptibility and plenty of topography in the
area will reduce the amount of rainfall needed to develop flash
flooding concerns. A general 1.5 to 2 inches of rain are expected
in the Edwards Plateau along the Rio Grande, likely falling in a
1-3 hour period as the storms track eastward down the plateau.
Thus, a higher-end Slight is in effect from Eagle Pass north and
west. As the storms move off the Rio Grande into central Texas,
generally towards San Antonio, they should weaken with time as they
separate from the dry line and the upper level shortwave rapidly
races away by the predawn hours Thursday. This should diminish the
flash flooding threat further east for this period.

Another area of more concentrated shower and thunderstorm activity
will impact the lower Mississippi Valley along the
Louisiana/Mississippi border Wednesday afternoon and evening. Due
to high FFGs and a lack of agreement in the guidance as to the
convective evolution, the area remains in a Marginal for now, but
should heavy rain producing storms move over an urban area such as
Baton Rouge, then flash flooding could occur. This area will need
to be monitored for a Slight Risk upgrade with future updates.

Wegman


Day 3
Valid 12Z Thu May 21 2026 - 12Z Fri May 22 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF THE
SOUTHERN PLAINS THROUGH THE OZARKS...

Numerous areas of showers and thunderstorms will impact the Slight
Risk area on Thursday through Thursday night. An ensemble of
guidance that covers the Day 3/Thursday period generally agree that
Thursday morning, the strongest storms will be across coastal Texas
through central Texas. These storms will track northeastward and
grow upscale as the impact areas from northern Louisiana, northeast
Texas, and Oklahoma. Thursday evening, a new round of storms
impacts south Texas as the rest of the storms push northeast into
Arkansas, northeast Oklahoma, and into Kansas, which then continue
northeast up the mid-Mississippi River Valley and a separate area
of storms impacts the Kansas City area. Despite this broad
evolution, there is very little confidence on how the storms will
behave/merge or track. Thus, the Slight covers likely more
saturated soils after rainfall expected in many of these areas on
Days 1 and 2. There will be no shortage of moisture and instability
across the Slight Risk area, especially the southern half, so it's
likely any limiting factor will be a generally progressive forward
speed to the storms, and cold pool interactions.

It's likely that with future updates, CAMs guidance should help
narrow down where the greatest threats for storms will be on
Thursday. This should allow the Slight to shrink a bit with better
confidence, though much of the region should see at least some rainfall.

Wegman
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 200800
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
400 AM EDT Wed May 20 2026

Day 1
Valid 12Z Wed May 20 2026 - 12Z Thu May 21 2026

...THERE ARE SLIGHT RISKS FOR EXCESSIVE RAINFALL OVER PORTIONS OF
SOUTHWEST TEXAS, AS WELL AS FOR EASTERN LOUISIANA INTO SOUTHERN MISSISSIPPI...

...Southwest Texas...

Numerous showers and thunderstorms are expected to develop over
much of southwest Texas, generally along the Rio Grande from south
Texas through the Edwards Plateau this afternoon into tonight.
Convection is likely to initiate over the mountains of Mexico and
along the dry line north and northeast of the Big Bend Region this
afternoon. Meanwhile a surge of deep Gulf moisture, characterized
by PWATs nearing 2 inches, will advect up the Rio Grande Valley on
a 15-25 kt southeast wind from the Gulf. Where the dry line and
this surge of moisture meet is where the heaviest and most
persistent showers and storms capable of producing heavy rain will
occur. This appears most likely in the portion of the Edwards
Plateau near Del Rio. A higher-end Slight remains in effect for
this area where the greatest potential of seeing 3 inches or more
of rain areally, with locally higher amounts exists. HREF
neighborhood probabilities peak over 30% of seeing 5 inches of rain
in this area. Given the steep topography, rocky soils, and
climatologically dry nature of the area, flash flooding appears
likely, especially where the storms are most persistent.

During the evening, the storms are likely to separate both from the
mountains of Mexico as well as the dry line. They will follow
generally parallel to the Rio Grande towards the southeast,
following the influx of deep Gulf moisture and instability. Due to
recent heavy rainfall from Laredo east through Corpus Christi, the
soils here are more saturated, and therefore should be more likely
to convert more rainfall to runoff, despite the storms by that
point likely being quite progressive. Thus, the Slight extends
south to around Laredo.

...Eastern Louisiana into Southern Mississippi...

In coordination with LIX/Slidell, LA and JAN/Jackson, MS forecast
offices, a small Slight Risk upgrade was introduced with this
update for eastern Louisiana into southern Mississippi. A stalling
out cold front over central Louisiana will provide the greatest
forcing for storms as it tries to progress eastward. Deep Gulf
moisture and instability will ramp up ahead of the front with peak
heating. However, thunderstorms may still be in progress along the
coast from the current storms over Texas. New convective initiation
will occur along the front, likely just east of the Mississippi
River in Mississippi, and those storms will link up with other
clusters of storms further south and west over southwestern
Louisiana. Since the front will be slow-moving, and there will be a
steady southerly flow of Gulf moisture out ahead of it, the storms
will likely have some training elements to them. During peak
heating in the mid to late afternoon, the storms will progress into
Baton Rouge and New Orleans, adding an urban element to the flash
flooding threat. Given the proclivities for those urban areas to
flash flood during heavy rain events, the Slight Risk upgrade was
introduced. The storms will then progress north into southern
Mississippi, which while far less urban, still has somewhat wetter-
than-normal soils, which could also promote flash flooding in some areas.

Wegman


Day 2
Valid 12Z Thu May 21 2026 - 12Z Fri May 22 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
SOUTHERN PLAINS AND PINEY WOODS REGIONS...

...Southern Plains into the Piney Woods...

The dry line across western Texas and Oklahoma will make a big push
to the east through the Day 2/Thursday period. The former cold
front over eastern Texas will retreat as a warm front towards the
north and as renewed push of deep Gulf moisture advects northward
with the low level jet. Further, a deep positively tilted longwave
trough will eject into the Plains from the Rockies during this
period. The combination off all of these factors will result in a
large and widespread area of convection stretching from the Gulf
Coast of Texas north across eastern Oklahoma and Kansas, as far
north as Kansas City.

Starting from the south, the convection along the Texas Gulf coast
will be associated with the dry line pushing quickly east and
running into plentiful Gulf moisture ahead of it. Expect most of
the storms from Houston south and west to be fast movers with the
dry line. Most of these storms will impact coastal communities
Thursday morning. Further north, there will likely be convection
ongoing at the start of the period across north Texas (near the
Wichita Falls area) and into southwestern Oklahoma. These storms
will increase in coverage through the morning as they progress over
central Oklahoma. Meanwhile by afternoon, the storms will blossom
over northeast Texas and down into northern Louisiana. With
moisture continuing to advect north, expect numerous clusters of
storms over much of eastern Oklahoma, eventually moving into
western Arkansas in the early evening. These areas got pockets of
1-3 inches of rain yesterday, so the newly saturated soils across
western Arkansas should support widely scattered instances of flash
flooding as multiple rounds of storms move through, and they
backbuild south and west. Due to the southerly flow of Gulf
moisture, some convection should also progress northward into
eastern Kansas and western Missouri through the evening. By this
far north instability will be lacking, so not expecting
particularly heavy rain, but all of the stronger storms to the
south will have merged into a larger area of moderate rain into
Kansas and Missouri, which have also seen heavy rains lately,
supporting Slight Risk levels of flash flooding. The steady rain
there could continue well into Thursday night.

...Southern Appalachians...

The clash of a cool air mass behind a back door cold front over
Virginia and tropical Atlantic moisture across the Southeast
characterized by PWATs over 1.5 inches will support areas of
showers and storms across portions of southwest Virginia, western
North Carolina, and perhaps into far eastern Tennessee Thursday
afternoon into Thursday night. Training convection along the front
will be likely, especially along the Virginia/North Carolina border
area, where the topography of the southern Appalachians could
locally further enhance rainfall rates. Instability will be
marginal however due to extensive cloud cover over this area.
While the meteorology may support a bit more widespread flooding,
the hydrology will be strongly working against that. A long-term
drought over the area and extremely dry soils compared to
climatology will make much of the rain expected in this area
beneficial. However, due to training, plentiful moisture that will
support areas of heavy rainfall, and the topography, isolated
instances of flash flooding are probable. For now the area remains
in a Marginal Risk, but a Slight may need to be considered if
forecast rainfall amounts in this area increase appreciably over
the next day or so.

Wegman


Day 3
Valid 12Z Fri May 22 2026 - 12Z Sat May 23 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER THE LOWER TO
MID MISSISSIPPI VALLEY, OHIO VALLEY, AND PORTIONS OF THE SOUTHERN PLAINS...

As a longwave trough over the northern Plains pivots northeastward
through the period, a surface cold front tracking along with it
will likely slow its eastward progress along the Mississippi and
Ohio Valleys. Plentiful Gulf moisture ahead of the front will
support numerous areas of convection all throughout the Marginal
Risk area. With the greatest upper level forcing moving away from
the front, it will become an increasing struggle to organize the
convection in a way such that flooding becomes more likely. From
the Ohio Valley to the Mid-Atlantic, plentiful cloud cover and much
cooler temperatures will keep the instability near zero, precluding
any meaningful heavy rainfall in favor of a long-duration light to
moderate rainfall. The heaviest rains appear most likely into the
far southern Appalachians (northern AL/GA, western Carolinas, and
Tennessee). This is the area that appears most likely to have a
Slight Risk upgrade with future updates. Elsewhere, other MCSs may
impact the lower Missouri Valley, and along the Texas coast. Dry
line convection into Friday evening may impact a good amount of
Oklahoma, but once again the storms do not appear to be able to
organize to increase the flooding threat beyond the
isolated/Marginal category.

Wegman
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 210808
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
408 AM EDT Thu May 21 2026

Day 1
Valid 12Z Thu May 21 2026 - 12Z Fri May 22 2026

...THERE ARE SLIGHT RISKS FOR EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHERN PLAINS AS WELL AS FOR THE UPPER TEXAS COAST INTO
SOUTHWEST LOUISIANA...

...Southern Plains...

The combination of several ingredients coming together across
eastern Oklahoma and north Texas will be the driver for rounds of
training convection expected across the area. At the surface, the
nose of a low level jet will advance northward over Oklahoma,
spiking the PWATs over 1.5 inches this morning. Surface convergence
around a trough will support low level lift and thunderstorm
formation. An approaching upper level trough will increase the
divergence and lift in the upper levels. The result will be a
rather narrow corridor at first with mostly showers but some
thunderstorms by early afternoon, as the day is approaching peak
heating. Cold pools and speed convergence will focus the
convection, allowing training to become more likely as the storms
track northeastward. A secondary wave of thunderstorms will move
northward across north Texas, which will increase the areal
coverage of convection into the early evening hours. The
strengthening upper level shortwave driving this secondary wave
will become the primary forcing, allowing the complex of weakening
storms tonight to push northward and end the rainfall threat from
south to north. While the greatest flash flooding threat may be in
a rather narrow corridor from north Texas north and east through
Tulsa, sufficient Gulf moisture could still allow for flash
flooding in other areas as well.

The inherited Slight Risk was split with this update owing to
better CAMs agreement that from north Texas through Oklahoma will
be the best area for flash flooding risk, but less rainfall is
expected across east central Texas, between Houston and the
Metroplex, allowing for a downgrade to the risk in that area.

...Upper Texas Coast into Southwest Louisiana...

A large complex of storms currently over South Texas will push
northeast up the Texas Coast through the day today. The area will
have abundant Gulf moisture, instability, and some limited support
from the upper levels. Thus, any storms will be capable of very
heavy rainfall, but the time of the heavy rainfall in any one area
may be limited as the complex progresses northeastward. The area
was hit hard with very heavy rain yesterday, resulting in rainfall
totals over 5 inches near Freeport. As this second round of storms
moves through this morning, convergence into the storms, sea breeze
effects, and the saturated soils from yesterday's rains could
result in additional instances of flash flooding. The storms
continue into the Houston Metro around midday, introducing an urban
factor to the flash flooding threat. The storms then turn more
northward through the afternoon, ending the flash flooding threat
for the day along the coast. To summarize, the Slight Risk, albeit
a low- end one, remains in place mostly for the potential for very
heavy rains with PWATs approaching 2 inches and the favorably wet
soils overcoming the fast movement of the storms to result in flash flooding.

Wegman


Day 2
Valid 12Z Fri May 22 2026 - 12Z Sat May 23 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE EASTERN U.S....

The inherited Marginal Risk was left largely unchanged for many
areas with this update, save some trimming across both Oklahoma and
Missouri due to reduced signal for heavy rainfall in those areas.
Two areas in particular stand out as higher-end Marginal Risks,
where a Slight may be needed with future updates:

Across a portion of the Ohio Valley from northern Kentucky through
southern Ohio, efficient moisture advection will spike PWATs from
around 1.25 inches early in the day Friday to 1.75 inches by the
afternoon. With this added moisture, so too will instability
increase. Rain in the form of showers and thunderstorms following a
warm front, the same wave that will impact the Slight Risk areas on
D1/Thu will increase in coverage at peak heating Friday afternoon.
Mostly stratiform rain will lead the convection in the morning,
helping saturate the soils that in some areas of the Ohio Valley
remain nearly saturated from prior days' rains. Then during the
afternoon as instability and moisture rapidly increase and the
cloud cover and relative stability push north into northern Ohio
and Pennsylvania, areas of showers and storms will impact northern
Kentucky into southern Ohio. There remains considerable uncertainty
as to how much instability can develop given the short time frame
between the morning's stabilizing rains with the warm front and the
following convection. Further, there is uncertainty as to how the
storms will organize, with some training needed to produce anything
more than isolated instances of flash flooding. Thus, for now, the
Marginal was maintained, but is likely the higher of the two areas
for a potential Slight risk upgrade with future updates.

The other area of the large Marginal that is drawing additional
scrutiny is the area from north Georgia into the Carolinas. Here
moisture and instability will be plentiful, supporting clusters of heavy-rain-producing thunderstorms. Winds are generally
unidirectional which may support training. However, lack of forcing
with upper level ridging in place will act as a counter to allowing
the storms that form to organize. Thus, clusters of disorganized
convection will be unlikely to produce much in the way of flash
flooding. Further, much of this area is in severe drought, and
soils are extremely dry. Sandy soils would work against flooding as
well into the Piedmont, so that highly unfavorable hydrology should
also work to effectively keep any flooding threat in check.

Wegman


Day 3
Valid 12Z Sat May 23 2026 - 12Z Sun May 24 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF EASTERN
TEXAS AND WESTERN LOUISIANA...

Perhaps the most active day of the Days 1-3 period will be on
Saturday across eastern Texas into Louisiana. Plentiful moisture
and instability will be drawn north off the Gulf, spiking PWATs to
around 2 inches in some areas, and instability could peak over
4,000 J/kg right at convective initiation midday/early afternoon
Saturday. Lines of intense thunderstorms will develop in this
extremely favorable air mass during the afternoon. The storms will
generally track northeastward. However, as they move north,
additional clusters are likely to form as both moisture and
instability rapidly recover. In the upper levels a series of small
shortwaves, but nonetheless potent ones given the highly favorable
atmosphere will allow for new clusters of storms to form across
southeast Texas soon after the prior rounds move off to the north.

Once daytime heating wanes in the evening, it appears likely that
additional storms that form will predominantly move southeastward
towards the Gulf as they follow the instability. This could lead to
additional periods of heavy rainfall over many of the same areas
hit with heavy rains Saturday afternoon. Further, these storms
moving against the prevailing windflow could slow down the storm
movement, increasing both interaction potential between cells as
well as the duration of the heavy rainfall, this threat appears
particularly probable in the Houston metro area. With CAMs input
over the next day or so, a Moderate Risk may need to be considered
in and around the Houston metro, perhaps extending southwest along
the Texas coast with future updates.

Elsewhere, the Marginal across portions of the Northeast was
removed with this update as the warm front over the area will have
zero instability to work with, resulting in a long duration
stratiform rain. Some elevated convective elements may sneak their
way that far north, but the otherwise light rainfall should allow
any rain to soak into the soils with no flash flooding expected.
Conversely, a Marginal Risk was introduced for a portion of north
Georgia into the Carolinas. Following likely rain from storms on
D2/Friday, additional widespread storms are expected again Saturday
afternoon into the evening over many of the same areas. As on
Friday, forcing in this area will be very limited. The storms will
generally track east-southeast towards the coast, with enough
movement that interactions are generally unlikely to initiate
additional convection. Any lines of storms should align
perpendicular to the flow reducing the training risk. Finally,
despite any rains on Friday, the ongoing severe drought should
still greatly mitigate most of the flash flooding threat. Given the
plentiful moisture and instability the storms will have to work
with, they will still likely produce very heavy rain in their
cores, raising resultant flooding potential into the Marginal category.

Wegman
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 220909
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
509 AM EDT Fri May 22 2026

Day 1
Valid 12Z Fri May 22 2026 - 12Z Sat May 23 2026

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL OVER THE UPPER
OHIO VALLEY AND THE SOUTHERN APPALACHIANS...

Shortwave energy embedded in broad southwesterly mid to upper
level flow from the western to central Gulf Coast, northeastward
through the TN/OH Valleys will persist through the upcoming day 1
period. These height falls/broad diffluent upper flow will enhance
uvvs in a large region of much above average PW values/anomalous
850-700 mb moisture flux, 2 to 2.5+/2-3+ standard deviations above
the mean respectively from the Gulf Coast northeastward into the
Ohio Valley. There is fairly good model consensus for the potential
for widespread moderate to heavy rainfall total in this anomalous
PW axis day 1. Simulated radars suggest cells will be fairly
progressive to the northeast. However, with potential for short
term training of cells and/or repeat rounds of convection, there
will be potential for runoff issues. Slight risk areas maintained
over the Upper OH Valley from northeast KY into southern OH where
FFG values are relatively low, and in the upslope region of the
Southern Appalachians from far northeast GA into the Upstate of SC
and western NC where heavy precip likely to focus in the region of
southerly low level flow. The slight risk areas fit well with the
axes of the HREF and RRFS means 2 and 3"+ probabilities.

Across the Southern Plains, a marginal risk area was introduced for
potential for additional convection Friday evening into the early
hours of Saturday. Additional shortwave energy expected to push
eastward into the Southern High Plains, supporting potential for
some organization to the associated convection late Friday into the
early hours of Saturday. Low confidence on details, with isolated
runoff issues possible where convection become organized.

Oravec


Day 2
Valid 12Z Sat May 23 2026 - 12Z Sun May 24 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF EASTERN
TEXAS AND WESTERN LOUISIANA...

Additional shortwave energy expected to move from far northeast
Mexico into southern and eastern Texas early Saturday, likely
setting the stage for another round of organized convection.
Building instability early Saturday, Mucape values reaching
2000-300 j/kg ahead of these height falls, in an axis of PW values
1.5-2.5 standard deviations above the mean, will support potential
for an organized line of convection to push across eastern and
southern TX Saturday morning into afternoon. The previous risk
areas were narrowed to better reflect the latest model qpf output
and the max RRFS 2 and 3"+ probability axes for the day 2 time period.

No significant changes made to the marginal risk area from the
Southern Appalachians into the Southeast. Southwest mid to upper
level flow with embedded shortwaves will continue across these
areas day 2. With PW values remaining well above average, 2 to 2.5+
standard deviations above the mean, additional widespread
scattered convection will likely produce locally heavy rainfall
totals. Both the HREF and RRFS show fairly high probabilities for
1"+/hr rainfall totals Saturday afternoon, supporting potential for
isolated runoff issues.

The marginal risk was also expanded northward from the previous
issuance into far eastern KS and large portions of MO to cover
areas the RRFS, GEM and FV3LAM are showing heavy rainfall totals day 2.

Oravec


Day 3
Valid 12Z Sun May 24 2026 - 12Z Mon May 25 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS THE UPPER
TEXAS COAST INTO SOUTHERN LOUISIANA...

A slow moving upper trof expected to amplify somewhat day 3 as it
pushes from eastern Texas into the Lower MS Valley. Similar to the
day 2 and day 3 period, there will continue to be an axis of much
above average PW values stretching from the Gulf Coast
northeastward into the Southeast/Southern to Central Appalachians.
There is a lot of spread day 3 with the QPF details, but still a
signal for widespread moderate to heavy rain potential in this
anomalous PW axis. A slight risk was maintained from the Upper TX
coast into southern LA, close to the WPC and NBM qpf max. This
covers the urban areas from Houston to New Orleans.

The marginal risk area was extended farther northeast through the
Southern to Central Appalachians where scattered convection likely
in the anomalous PW axis, supporting locally heavy rainfall
amounts and potential for isolated runoff issues.

Oravec
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 230808
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
408 AM EDT Sat May 23 2026

Day 1
Valid 12Z Sat May 23 2026 - 12Z Sun May 24 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF EASTERN
TEXAS AND WESTERN LOUISIANA...

Convection across the Southern Plains early this morning will
likely remain active in the post 1200 UTC period Saturday in an
overall favorable convective pattern over the Southern Plains into
the Lower MS Valley. There is a strong signal for widespread
heavy precip day 1 across eastern/southern TX into southern LA as
additional shortwave energy moving east northeastward from far
northeast Mexico into southern and eastern Texas early Saturday
enhances large scale uvvs. HREF and RRFS neighborhood probabilities
are high for 1 and 2"+ totals day 1 in the slight risk area.
Several of the latest CAMS, ARW2, GEM, NAMNEST and FV3LAM show
potential for a period of training of cells across the Upper TX
coast into southwest LA late morning into this afternoon. Across
these areas, the HREF and RRFS neighborhood probabilities are high
for 3"+ totals and the HREF probabilities high for 5"+ totals.
There is potential for these heavier totals affecting the urban
areas from Houston to Lake Charles, where an upgrade to a moderate
risk was considered and will be re-evaluated after viewing the 1200
UTC hi-res guidance as per collaboration with affected NWS WFOs.

No significant changes made to the marginal risk area from the
Southern Appalachians into the Southeast. Southwest mid to upper
level flow with embedded shortwaves will continue across these
areas day 1. With PW values remaining well above average, 2 to
2.5+ standard deviations above the mean, additional widespread
scattered convection will likely produce locally heavy rainfall
totals. Both the HREF and RRFS show scattered areas of fairly high probabilities for 1"+/hr rainfall totals Saturday afternoon,
supporting potential for isolated runoff issues.

Over the Upper OH Valley region, a marginal risk area was added for
potential for additional scattered convection and locally heavy
rains into this afternoon. This additional scattered heavy precip
will fall across areas that have received 1-2" of rain over the
past 24 hours, raising soil moisture and stream flows and lowering
FFG values. Isolated runoff issues possible across these areas.

Oravec


Day 2
Valid 12Z Sun May 24 2026 - 12Z Mon May 25 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS THE UPPER
TEXAS COAST INTO SOUTHWESTERN LOUISIANA...

A slow moving upper trof expected to amplify somewhat day 2 as it
pushes from eastern Texas into the Lower MS Valley. This will
likely help fire another round of convection in the vicinity of the
Upper TX coast, eastward into southern LA. At the moment, it
appears the best instability ahead of this next closed low will be
suppressed southward into the northern Gulf in the wake of the
active day 1 convection. This may support the heaviest rains being
shunted southward and off the coast day 2, as suggested by the RRFS
mean and the FV3LAM. There is still a lot of model spread, but WPC
qpf has trended south, with the heaviest offshore. Subsequently,
the previous slight risk area has been trimmed on the north end,
confined to the far Upper TX coast into southwest LA. There may be
overlap of the day 1 and day 2 heavy rain areas over the Upper TX
coast into southwest LA. However, at the moment, the risk level was
maintained as slight as there is still model spread with the day 2
heaviest qpf axis.

No significant changes made to the previous broad marginal risk
area extending northeastward from the Central Gulf Coast, across
the South and into the Southern to Central Appalachians. Similar
to the day 1 period, there will continue to be an axis of much
above average PW values stretching across these areas, with
embedded shortwaves in the broad southwesterly mid to upper level
flow, supporting widespread scattered convection, locally heavy
rains and isolated runoff issues.

Oravec


Day 3
Valid 12Z Mon May 25 2026 - 12Z Tue May 26 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS THE
SOUTHERN APPALACHIANS...

A small slight risk area was introduced in the vicinity of the
Southern Appalachians from north Georgia into the Upstate of SC and
far southwestern NC. A very broad region of much above average PW
values, 2 to 2.5+ standard deviations above the mean, will stretch
from the Central gulf coast, northeastward across the South,
Tennessee Valley, Southern Appalachians and into the Southern Mid-
Atlantic during day 3. Similar to the day 2 period, broad south
southwesterly mid to upper level flow with embedded shortwaves will
support additional widespread scattered convection across these
areas. While locally heavy rains are likely across a large region
in this anomalous PW axis, there is model signal for concentration
of heavy precip into the upslope regions of the Southern
Appalachians, with a small slight risk area depicted here. Included
the Atlanta metro in the slight risk area given the sensitivity to
potential urban issues. There may be additional slight risk areas
in this anomalous PW axis depicted in future updates, but low
confidence with placement at this time.

Oravec
$$
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* Origin: Project Scorpio TEST (618:250/6)