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

FOUS30 KWBC 280734
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
334 AM EDT Thu May 28 2026

Day 1
Valid 12Z Thu May 28 2026 - 12Z Fri May 29 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS MUCH OF
THE SOUTHEAST TO MIDDLE MISSISSIPPI VALLEY, SOUTHEAST FLORIDA, AND
FOR PORTIONS OF THE NORTHWEST...

...Central Plains to Southeast...

A bit of an omega block pattern is shaping up across the CONUS
with a broad upper trough axis fixated over the Central and
Southern Plains with ridging in place over the top. This will cause
a rather chaotic flow under the mean trough and several smaller
mid- level perturbations basically "stuck" within the overall
trough axis. Ample instability with deep moisture presence will
certainly continue to support at least a scattered heavy rain
footprint across areas underneath influence of the trough.
Scattered elevated probabilities between 30-70% exists for
localized amounts >3" from KS all the way into the Southeast U.S.
with the maxima split between eastern KS to northern AR and the
Central Gulf coast. For KS/AR, parked underneath the upper trough,
upper forcing and stagnant flow are more favorable for heavier
rainfall totals. Maintaining a marginal risk at this time as the
heaviest rainfall over the past 12 or so hours was more southwest
of where the guidance is showing today and the rest of the region
is still somewhat dry and can probably support some heavier totals.
Along the Gulf Coast and into the Southeast, instability will be
maximized in this area with weak flow supporting slow- moving
convection and heavier rainfall over those isolated areas.
Antecedent conditions across much of this region are also very wet,
so it may not take much to cause issue. Given the still fairly
isolated nature, maintaining a broad marginal risk, with any
possible upgrades today stemming more from near term radar trends.

...Florida...

An active sea breeze pattern with weakening steering flow will
lead to periods of heavy rainfall across southeast Florida this
afternoon. Greatest concern remains over the South Florida metro
corridor from West Palm Beach to Miami. Latest HREF is robust with
showing greater than 50% probabilities for 3" in 24-hours, with
even some modest, albeit localized, probabilities for 5". This
correlates well with CAM guidance, with some indicating bullseyes
of greater than 3" within the larger QPF footprint. Locally
significant rainfall is likely in this relatively classic pattern
with ample moisture and instability present. A marginal risk
remains in effect across Southeast Florida.

...Washington/Oregon...

A deep upper level low over the West will allow for a broad axis
of diffluent flow across the interior Northwest. Precipitable water
values 1-1.5" are in the 90-90th percentile, and with sufficient
instability, should support convection capable of producing heavy
rainfall. Flooding and flash flooding are a concern for mainly the
more vulnerable areas - urban, small stream, and low lying areas.
HREF 24-hr probabilities for greater than 3" are between 40-70% for
especially the Oregon cascades. Given the favorable environment
though, a marginal risk extends all the way from far northern
California northward to the eastern half of Washington state. A
previous marginal risk for parts of the northern Rockies was
trimmed out for this update given the lack of QPF signal.

Santorelli


Day 2
Valid 12Z Fri May 29 2026 - 12Z Sat May 30 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PARTS OF
THE NORTHERN ROCKIES AS WELL AS MUCH OF THE SOUTHEAST TO MIDDLE
MISSISSIPPI VALLEY...

...Eastern Washington to Northern Rockies...

A marginal risk is in place across far northeast Washington to
northwest Montana due to an increase in the heavy rainfall signal
for this period as the upper low over the West on Day 1, pivots
slightly northeastward, placing this region in an area with better
upper forcing and advection of moisture. The presence of anomalous
moisture and some instability may present a threat for localized
heavy rainfall and flash flooding, especially for burn scar
locations within this region.

...Middle Mississippi Valley to the Southeast...

Strong Canadian high pressure pressing in from the north will
allow for a slow moving cold front to press south over the course
of Thursday into Friday with convection likely to spawn along and
ahead of the front and dry air advecting behind the front leading
to a quick cutoff of activity. The front will arc back into the
Tennessee Valley to Middle Mississippi Valley, supported by the
persistent troughing over the south-central Plains. A moist and
unstable environment near and south of this front will support
scattered convection, with some heavier cells likely within the
pattern. It is still too hard to pick out any discernible areas of
interest, so maintained a very broad marginal risk over this area
which is quite wet and will continue to be in the Day 1 period.

Santorelli


Day 3
Valid 12Z Sat May 30 2026 - 12Z Sun May 31 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS THE
NORTHERN ROCKIES TO HIGH PLAINS AND THE SOUTHEAST...

...Northern Rockies to High Plains...

The upper level low over the West during the Day 1 and 2 periods
will weaken and shift northeastward, moving over the Northern
Rockies to High Plains region on Day 3/Saturday. Moisture anomalies
will continue to be in the 90-90th percentile, supporting moderate
to heavy rainfall, with widespread QPF greater than 0.5-1" likely
across western and central Montana. There may not be a lot of
instability to work with, so any flood or flash flood threats
should be mainly localized with particular attention to burn scar
locations. A fairly broad marginal risk is in place across much of
western and central Montana, into parts of northern Wyoming as well.

...Southeast...

Same story as Days 1 and 2, with ample moisture and instability
present near and south of a cold front that may stall over the
region on Saturday supporting convection, across much of the
Southeast. Some of this region, especially western parts of South
Carolina and into the Appalachians has been very wet as of late and
is well primed, so may be more favorable for flooding concerns.
The marginal risk though continues towards the coast due to the
presence of a weak frontal wave in the region. The Marginal Risk
extends from the Southeast coast, westward into northeast Alabama
and southeast Tennessee.

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

FOUS30 KWBC 290829
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
429 AM EDT Fri May 29 2026

Day 1
Valid 12Z Fri May 29 2026 - 12Z Sat May 30 2026

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

Largely maintained the previous Slight Risk area that was introduced
in the Southeast US. A sheared 500mb vorticity maximum approaching
from the west will be encountering a moist airmass with increasing
amount of instability later during the day and evening. The latest
numerical guidance kept expected precipitable water values in the
2 to 2.25 inch range along and south of a quasi-stationary front
draped across the region from the TN Valley to the SC coast.
Instability will be highest over AL on east into central and
southern GA with MUCAPE between 1,000-2,000 J/kg most often. MUCAPE
up to 1,000 J/kg will be available later tonight from the Savannah
River to coastal SC. This combination should be enough to support
and sustain localized rainfall rates in excess of 2 inches per hour
where warm rain processes predominate from eastern AL eastward to
the Savannah River this afternoon and tonight.

...Middle Mississippi Valley to the Southeast...

The western portion of the front affecting the Southeast US will
extend into portions of the Middle Mississippi Valley and provide
the focus for showers and thunderstorms...some of which may produce
locally heavy rainfall from the Tennessee Valley into the Middle
Mississippi Valley into tonight.

...Eastern Washington to Northern Rockies...

A marginal risk remained in place across far northeast Washington
to northwest Montana due to an increase in the heavy rainfall
signal for this period as an upper low over the West on Day 1
places this region in an area with better upper forcing and
advection of moisture. The presence of anomalous moisture and some
instability may present a threat for localized heavy rainfall and
flash flooding, especially for burn scar locations within this region.

Bann


Day 2
Valid 12Z Sat May 30 2026 - 12Z Sun May 31 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS THE
NORTHERN ROCKIES TO HIGH PLAINS AND THE SOUTHEAST...

...Southeast...

Latest numerical guidance has shifted a majority of the rainfall
eastward enough compared with previous runs to preclude an upgrade
to a Slight risk. In addition...the spread of model
guidance both in terms of placement and amounts precluded an
upgrade. As mentioned previously...some of the region, especially
western parts of South Carolina and into the Appalachians, has
been very wet as of late and is well primed, so may by more
vulnerable to flooding concerns.

...Northern Rockies to High Plains...

The upper level low over the West during the Day 1 period will
weaken and shift northeastward, moving over the Northern Rockies to
High Plains region on Saturday. Moisture anomalies will continue
to be in the 90-90th percentile, supporting moderate to heavy
rainfall, with widespread QPF greater than 0.5-1" likely across
western and central Montana. There may not be a lot of instability
to work with, so any flood or flash flood threats should be mainly
localized with particular attention to burn scar locations. A
fairly broad marginal risk remained in place across much of
western and central Montana, into parts of northern Wyoming as well.

Bann


Day 3
Valid 12Z Sun May 31 2026 - 12Z Mon Jun 01 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE NORTHERN ROCKIES AND THE SOUTHEAST UNITED STATES...

...Northern Rockies and Adjacent High Plains...
The upper level low which has been supporting the prolonged wet
period over the Northern Rockies will continue to move northward
across Montana slowly on Sunday. This results in surface low
pressure and associated surface front to makes its way out over the
Plains and gradually weaken while the mid and upper level
circulation keeps precipitation lingering over Montana and far
northern Wyoming. Moisture remains anomalously high but instability
still looks to be dependent upon cloud cover. As in the Day 2
period...any flood or flash flood threats should be mainly
localized with particular attention to burn scar locations.

...Southeast...

Until surface high pressure builds far enough southward into the
Southeast states to decrease coverage of lingering convection on
Sunday evening...the antecedent conditions keep a risk of flooding
concerns over the area.

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

FOUS30 KWBC 300830
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
430 AM EDT Sat May 30 2026

Day 1
Valid 12Z Sat May 30 2026 - 12Z Sun May 31 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF MONTANA...

...Northern Rockies to the Plains...

Maintained the Slight risk across portions of Montana as a mid-
and upper-level system makes its way northward slowly today. The
system should foster locally intense rainfall rates...especially in
the eastern portion of the Slight Risk area...given moderately
steep lapse rates and some potential for enough breaks in cloud
cover. The HREF neighborhood probabilities of exceeding 1"/hr in
the 30-50% range, and 2"/hr around 10%. This results in HREF FFG
exceedance probabilities broadly over 25 percent. The RRFS shows a
similar evolution in roughly the same area but was not quite as
high with its probability of exceedance or with the probability of
1 inch per hour rainfall. Farther west;..the instability is
expected to be weaker but the greater coverage of rainfall looks
to offset the instability shortfall. As mentioned previously...the
flood risk should gradually transition from flash flood to areal
flood/river flood as you go west across the state.

A Marginal Risk area extending eastward from Montana and then
southward from the Northern Plains and Mid-Mississippi Valley was
largely left in place given the signal in the HREF for locally
heavy rainfall rates within an elongated moisture plume originating
from the Southeast US. It was done so despite convective details
remaining uncertain. The most organized convective threat may end
up over portions of NE and SD given a highly difluent flow aloft
and low level convergent flow. However, there are also signals of
organized convective clusters within the moisture axis anywhere
from Arkansas to Iowa, While convection is unlikely along this
entire axis...where it does develop rainfall rate potential will be
high enough for localized flash flooding.

...Southeast...

Latest numerical guidance continued to show locally heavy rainfall
today and tonight along and south of a boundary moving in from the
north. There was a bit of a westward expansion in the western
extent shown by the HREF and RRFS of the 1-inch per hour
probabilities and the probability of exceedance. As a result...the
Marginal Risk was expanded westward in parts of Georgia to Alabama.

Bann


Day 2
Valid 12Z Sun May 31 2026 - 12Z Mon Jun 01 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL STRETCHING FROM
MONTANA TO NORTHERN FLORIDA...

Any heavy to excessive rainfall should be located in or near a
plume of anomalous moisture plume that will extend from Montana
into the Southeast United State. Large scale forcing is more
subtle outside of the Northern Plains/Rockies...but there should be
some weak shortwave energy embedded within the weak flow that will
make them difficult or impossible to time. As this shortwave energy
encounters a late day atmosphere with MUCAPE values in excess of
3000 J per kg from the Plains into the Mississippi Valley and parts
of the Southeast US...storms have the potential to produce very
intense rainfall rates that approach or exceed flash flood
guidance along this entire corridor. A large and generally
unfocused Marginal Risk area still seems to handle the localized
nature of flash flood risk that should exist.

The Montana portion of the Marginal Risk has the strongest synoptic
forcing as a mid- and upper-level system gradually moves north of
the border...keeping the western part of the state in lingering
wrap-around rainfall before gradually tapering off.

Bann


Day 3
Valid 12Z Mon Jun 01 2026 - 12Z Tue Jun 02 2026

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

There are some hints in the guidance that the overall risk of
excessive rainfall is non-zero over the Plains from Kansas into
Colorado as models show a low level axis of moisture and
instability moving northward on Monday afternoon. The ensemble and deterministic QPF is fairly low...perhaps due to a component of low
level flow off the moisture. In addition...lingering deep moisture
may fuel some late day thunderstorms on Monday that are capable of
locally heavy rainfall but the model spread limits confidence.

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