FOUS30 KWBC 260747
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
347 AM EDT Tue May 26 2026

Day 2
Valid 12Z Wed May 27 2026 - 12Z Thu May 28 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS THE EASTERN
HALF OF TEXAS, PORTIONS OF THE LOWER MISSISSIPPI VALLEY, AND AREAS
OF THE OHIO VALLEY TO CENTRAL APPALACHIANS...

...Texas to Lower Mississippi Valley...

The broad upper level evolution occurring upstream over the
Southern Plains will continue to shift east with the large scale
forcing driving into the eastern half of TX leading to heavy rain
prospects over the eastern portions of Hill Country, the I-35
corridor and much of east TX, including the middle and upper TX
coastal areas on Wednesday. Environmental conditions for heavy
rainfall are most favorable along the TX and LA Gulf coast areas
with a corridor of elevated theta_E's aligned from Corpus Christi
up through the Lower Sabine to about 100 miles inland. The setup is
contingent on the behavior of the convective pattern upstream into
the central portion of the state and the migration of the
thunderstorm complex exiting out of I-35. The general consensus is
the maxima for precip will likely occur in proximity to the same
areas that were hit within the past week; the area along the upper
TX coast from Houston up to Lake Charles. This is very well defined
within the probability fields in both the HREF and the AIFS-ENS
where >3" is likely (60-90%) within the confines of that zone with
the HREF even signaling modest >5" potential (40-60%) in that same
zone. There's still some uncertainty in the behavior of any
mesoscale complexes that end up materializing from all the
convective development the previous evening and if they cause any
significant shifts in the potential. In this case, this leads to a
broad SLGT risk with a MRGL risk encompassing over the Southern
Plains to Lower Mississippi Valley as broad upper forcing will
likely spur scattered convection all across areas from western KS
down through OK in the setup. Areas away from east TX and the Lower
Mississippi will have more isolated heavy rain prospects,
comparatively, so the threat remains elevated in the SLGT risk
within these particular locations.

...Ohio Valley...

Conditions will become increasingly favorable for heavy rainfall
across the Ohio Valley going into Wednesday from a multitude of
features that will ultimately couple into something more formidable
during peak diurnal instability. Sheared vorticity stemming from
previous period convection will likely settle over the central Ohio
Valley with a west to east bisecting quasi-stationary front
positioned just north of the Ohio River basin. A sweeping trough
exiting out of Ontario will help tighten an axis of confluence
across the Midwest and Ohio Valley by Wednesday afternoon, enticing
a squeeze of the thermal gradient and regional instability axis
that aligns with the frontal placement. Destabilization by the
afternoon hours will lead to scattered to widespread thunderstorm
initiation along the boundary with convective episodes likely to
spawn heavier cells capable of hourly rates between 1-2"/hr as PWAT
anomalies sit firmly within +2 standard deviations above climo.
Previous periods of rainfall in the last three to four days have
really brought down the areal FFG markers for all 1/3/6 hour
thresholds with a vast majority of places along the Ohio River
basin and points north running <1"/hr in the hourly exceedance
indicator. This points to any heavier convective impacts could
cause issues with the remnant soil moisture and hydrologic
concerns that are lingering after the last event. This is
especially true for eastern OH, southwest PA, and western WV where
complex topography only exacerbate the potential in these zones.
3-hour FFG exceedance probabilities from the 00z HREF are between
20-40% for a large portion of eastern IN through the southern half
of OH into southwest PA with a maxima of 40-60% located across
northwest WV between US50 and WV7. Considering the antecedent
conditions and expected widespread convective regime along the
front, a SLGT risk was added for an increasing threat for flash
flooding Wednesday.

Kleebauer


Day 3
Valid 12Z Thu May 28 2026 - 12Z Fri May 29 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE CENTRAL AND SOUTHERN PLAINS, LOWER MISSISSIPPI VALLEY, AND
SOUTHEAST FLORIDA...

...Plains to Lower Mississippi Valley...

Breakdown of the persistent pattern for areas east of the
Continental Divide will lead to weaker steering flow, but still
enough moisture, lingering boundaries, and remnant mid-level
vorticity to spur up bouts of scattered convection all across parts
of the Central and Southern Plains into the Mississippi Valley.
This setup is a far cry from what we've experienced the past
several days, so the prospects of widespread flash flooding are
much lower comparatively. However, environmental conditions and
deep moisture presence still remain favorable along the northern
periphery of the trough lingering across east TX which places the
best opportunity for convective episodes to be located over the
aforementioned areas. Ensemble QPF footprint is most notable across
the Central Gulf coast and upper TX coastal plain, likely in part
to the positioning of the trough and the fact the most prevalent
theta_E is situated along the immediate Gulf. It's a period to
monitor for any small scale features that could enhance convective
potential further, but for now, a broad MRGL exists to cover for
the threat.

...Florida...

Active sea breeze pattern with weakening steering flow will lead to
a period of heavy rainfall across the southeast FL coast on
Thursday afternoon. Consensus within guidance is for an active
period between 18-00z Thu/Fri that would allow for heavy convection
with slow forward propagations to impact the South Florida metro
corridor from West Palm Beach down to Miami. Globals and regional
guidance even have some 2+" totals already in the output, and
that's before the CAM's even have a depiction. Typically, this is a
sign for heavy rainfall prospects capable of flash flooding,
especially when you consider the PWATs running +1 to +2 deviations
across that area of the Peninsula. A MRGL risk remains for that
urban corridor of southeastern FL.

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

FOUS30 KWBC 271225
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
825 AM EDT Wed May 27 2026

Day 2 Valid 12Z Thu May 28 2026 - 12Z Fri May 29 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE CENTRAL AND SOUTHERN PLAINS, NORTHERN ROCKIES, LOWER
MISSISSIPPI VALLEY, AND SOUTHEAST FLORIDA...

...Plains to Lower Mississippi Valley...

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 with ridging in place over the top. This will cause a
rather chaotic flow under the mean trough with deep moisture and
several smaller mid-level perturbations basically "stuck" under the
the overall trough axis. Ample instability with deep moisture
presence will certain be a cause for continuing at least a
scattered heavy rain footprint across areas under the influence of
the trough. Scattered elevated probabilities between 30-60% exists
for localized amounts >2" from KS all the way into the Southeast
U.S. with the maxima split between KS and the Central Gulf coast.
The two areas are different in the reasoning as the primary center
of the trough will be fixed over KS leading to the best upper
forcing pattern and stagnant flow remaining parked over the area as
we move through D2. Pending the amount of rain that falls over the
course of D1, a targeted upgrade is possible, but maintained the
MRGL and will reassess as we move forward in future updates to see
if an upgrade is warranted. The Central Gulf coast will remain in a
favorable instability maxima with weak flow likely a component that
could lead to isolated heavy totals stemming from slow-moving
convection. The area from the Upper TX coast over through southern
GA has been leaning wet over the past week, so antecedent
conditions are a little more unforgiving for these types of setups.
In any case, the threat remains modest, at best, so the MRGL risk
was sufficient for the pattern with any upgrades likely to stem
from more near term sampling of the radar trends.

...Florida...

Active sea breeze pattern with weakening steering flow will lead
to a period of heavy rainfall across the southeast FL coast on
Thursday afternoon. Consensus within guidance is for an active
period between 18-00z Thu/Fri that would allow for heavy convection
with slow forward propagations to impact the South Florida metro
corridor from West Palm Beach down to Miami. Latest 00z HREF is
modestly robust with the signature for at least 3" off the
neighborhood probabilities with a steady 60-90% output along the
southeastern coast of FL with the maxima generally confined to the
Miami Metro up to West Palm Beach. This correlates strongly with
what has been advertised via regional and global guidance the past
few days with the deterministic CAMs even indicating some 4-6"
bullseye's within the main QPF footprint. This is a relatively
classic pattern capable of locally significant rainfall within a
deep moisture presence as PWAT anomalies sit between +1 to +2
standard deviations within the various ensemble packages. A MRGL
risk remains in effect for the period across the South Florida
metro corridor.

...Northern Rockies...

Maturing ULL over the west coast will allow for a broad axis of
diffluent flow across the interior northwest with the highlight of
scattered convection likely to pivot further west into eastern WA,
northern ID, and the western slopes of the Northern Rockies.
Signals are not as prevalent compared to previous periods, however
the environmental conditions are still favorable, especially when
it comes to PWAT anomalies still generally running between the
90-95th percentile across northeast WA into northern ID. Burn scar
remnants will likely be the most susceptible to seeing impacts, so
the threat remains low-end and generally localized. Maintained
continuity from the previous forecast with a MRGL risk in place
across the aforementioned areas.

Kleebauer


Day 3 Valid 12Z Fri May 29 2026 - 12Z Sat May 30 2026

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

Strong Canadian high pressure pressing in from the north will lead
to a persistent quasi-stationary turned cold front to press south
over the course of Thursday into Friday with convection likely to
spawn along and ahead of the front with dry air advecting behind
the front leading to a cutoff of activity. Jury is still out on
specifics with the placement of the front generally over the
Carolina's by Friday morning with slow push south as the day wears
on. Frontal alignment is more of a arcing back into the Tennessee
Valley as the persistent troughing in the South-Central Plains will
likely maintain some southerly flow for areas along and west of the Mississippi. Anywhere within proximity to this front will be
subject to various convective outputs with some heavier cells
likely intertwined in over the pattern. No discernible areas of
interest are present at this juncture, however the environmental
favorability likely points to the best chances occurring across
the Southeast into the lower Tennessee Valley. A broad MRGL is
forecast for the above areas through the Lower Mississippi Valley.

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