FOUS30 KWBC 120810
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
410 AM EDT Sun Apr 12 2026

Day 1
Valid 12Z Sun Apr 12 2026 - 12Z Mon Apr 13 2026

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR CENTRAL TEXAS...

...Central Texas...

Broad troughing in the west will continue to direct sheared 500mb
vorticity maxima at the Southern Plains as a narrow 250mb jet
streak over the Central Plains places its divergent right-entrance
region over central and southern TX. Between the trough in the West
and high pressure over the Southeast, a strong IVT exceeding 500
kg/m/s will engulf much of the Southern Plains with 1,000-2,000
J/kg of MLCAPE. Convection will fire up along and ahead of the
dryline during the afternoon and evening hours. Vertical wind
shear and low-level helicity will be sufficient to support strong-
to- severe storms, but the uncertainty lies in the orientation of
surface troughs and outflow boundaries that reinvigorate storms
Sunday night, and where they are located. Some CAMs show some more
progressive segments of storms, while others show potential for
back-building and training.

12Z HREF guidance, specifically 24-hr QPF probabilities, show
moderate chances (40-60%) for rainfall totals >2", with the bulk of
the rainfall coming after 18Z and before 12Z Sunday. There are some
low chance probabilities (20-30%) along I-35 from San Antonio to
Austin. Southern and eastern TX badly need rainfall (UNL drought
monitor shows severe drought in many places), but excessive
rainfall rates approaching 2"/hr over very dry/hard ground can
become hydrophobic. Add in the metro areas at risk (I-35 corridor)
and the inherited Slight Risk still looks to be on track.

The expansive area of anomalous moisture (>90th climatological
percentile per NAEFS) extends as far north as eastern OK, southeast
KS, and southwest MO. Excessive Rainfall in these areas will be
largely driven by the aforementioned 250mb jet streak as southerly
850mb winds inject the moisture into this divergent setup aloft.
Soundings are not as saturated and storm motions are faster, thus
supporting the Marginal Risk currently in place.

...Northern Michigan...

A Marginal Risk remains in effect for this period. Anomalous Gulf
moisture pumping northward will interact with the draped frontal
boundary to bring enhanced rainfall to the region. NAEFS continue
to show PWs and IVT values that are above the 99th climatological
percentile that features a combination of saturated soils and
lingering snowpack. Accumulations of 1 to 2 inches are anticipated
for the northern half of Mitten which may cause any lingering
snowpack to melt and possibly exacerbate the flooding potential on
Sunday.

Campbell/Mullinax


Day 2
Valid 12Z Mon Apr 13 2026 - 12Z Tue Apr 14 2026

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF
THE UPPER MISSISSIPPI VALLEY AND UPPER GREAT LAKES REGION...

Another round of showers and thunderstorms will move through the
Upper Mississippi Valley and Great Lakes during the afternoon and
evening hours, prolonging the threat for excessive rainfall,
increased snow melt and flash flooding. A Marginal Risk
remains in effect from eastern Minnesota to northern Michigan.

Campbell


Day 3
Valid 12Z Tue Apr 14 2026 - 12Z Wed Apr 15 2026

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FROM THE TEXAS
HILL COUNTRY TO THE UPPER MIDWEST/GREAT LAKES REGION...

Multiple rounds of strong to severe thunderstorms expected from
Texas to the Midwest states, given favorable wind shear and
instability in place as multiple impulses eject across the Plains.
Gulf moisture will be funneling northward between the trough over
the Rockies and the ridge over the eastern states. The environment
will be favorable for a few mesoscale convective systems to
develop and the limited eastward progression will likely result in
areas that have excessive rainfall leading to some instances of
flash flooding. A Marginal Risk area span from the Texas Hill
Country northeastward to the Midwest and western Great Lakes.

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