FOUS30 KWBC 240804
QPFERD

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

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

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

...Central Plains into Ohio Valley...

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

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

...Gulf Coast...

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

...Northern Plains...

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

Kleebauer


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

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

...Midwest through Great Lakes...

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

...Gulf Coast...

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

...Northern Plains...

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

...Northeastern California and Northwest Nevada...

Almost a carbon copy of the prior period for convective impacts
lingering across the Northern Sierra up through northeastern CA and
northwest OR. The upper pattern is pretty slow to breakdown with
the diffluent area in the longwave setup still situated over
northern CA into NV. Modest instability and slightly above normal
moisture in the terrain will offer the capability for some isolated
flash flood concerns within any complex terrain and burn scar
remnants in the above area. Precip maxima will be limited to ~1",
so the threat lies within the lower threshold of a MRGL risk, which
is what is now forecast.

Kleebauer
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