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FOUS30 KWBC 310805
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
405 AM EDT Sun Aug 31 2025

Day 1
Valid 12Z Sun Aug 31 2025 - 12Z Mon Sep 01 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM SOUTHERN NEW
MEXICO INTO WEST/CENTRAL TEXAS AND FOR EASTERN NEBRASKA...

Abundant instability and moisture influx will help maintain
convection over the Plains. High rain rates combined with nearly
saturated soils from recent heavy rain/storms will keep an elevated
threat for flash flooding for the region. A Slight Risk clips far
southeast South Dakota, eastern Nebraska, eastern Kansas, northwest
Missouri and western Iowa.

Easterly flow will allow storms that develop over the Gulf to move
into the coastal areas of Texas and western Louisiana. Meanwhile
the stalled frontal boundary over the area will continue to provide
forcing into the rest of Texas and New Mexico. For many areas, dry
clay soils will allow for most of the rainfall in the typically
dry desert areas to convert to runoff quickly. The better focus
for higher QPF will be for locations near or east of the Hill
Country across eastern Texas. A Slight Risk spans from southeast
Arizona to the southeast coast of Texas within a broader Marginal
Risk for the southern tier and portions of the Central/Northern
Plains.

Campbell

Day 2
Valid 12Z Mon Sep 01 2025 - 12Z Tue Sep 02 2025

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR THE
SOUTHERN TIER, PLAINS AND TENNESSEE VALLEY...

A frontal system and a shortwave or two aloft will support storms
with higher rain rates across the Lower Missouri/Mid-Mississippi
Valley and the Tennessee Valley to Southern Appalachians. The
Marginal Risk areas for the Tennessee Valley and for the Plains
remain in effect for this period.

The stalled frontal boundary along the Gulf Coast and into Texas is
expected to advance a little southward during this period leading
to the QPF footprint being offset from prior days which will limit
the flooding potential. The heaviest rain is still expected to
focus along the I-10 corridor from Houston to San Antonio and may
still cause impacts. A broad Marginal Risk remains in effect from
the Southwest, southern Texas/western Gulf coastline an much of the
Florida peninsula.

Campbell


Day 3
Valid 12Z Tue Sep 02 2025 - 12Z Wed Sep 03 2025

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTHWEST/CALIFORNIA, FLORIDA, LOWER MISSISSIPPI/TENNESSEE
VALLEYS AND THE UPPER MIDWEST...

A Marginal Risk area was maintained for the Mid-South as shortwave
energy and a weak low traversing the cold front may trigger
convection capable of higher rainfall rates over the region.
Meandering frontal boundaries within an unstable environment will
support heavy rainfall and localized flash flooding potential for
Florida, therefore the Marginal Risk area was kept for this period.

A cold front will drop into the Northern Plains and Upper Midwest
ahead of the strong reinforcing upper trough. Convection is
expected fire up along and ahead of the frontal boundary, with
potential for heavy rainfall. A Marginal Risk area is in effect for
the eastern Dakotas, northern Iowa, Minnesota, northern Wisconsin,
and portions of the UP of Michigan.

Meanwhile, monsoonal moisture is forecast to flow into the
southwestern U.S. underneath the mean upper ridge for scattered
showers and thunderstorms. A Marginal Risk span from southern
Colorado/New Mexico westward to eastern California.

Campbell


Day 1 threat area: https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Day 2 threat area: https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Day 3 threat area: https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt