Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
858 PM EDT Fri Aug 8 2025
Day 3
Valid 12Z Sun Aug 10 2025 - 12Z Mon Aug 11 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FROM FAR NORTHERN
MISSOURI THROUGH MUCH OF EASTERN IOWA AND INTO SOUTHWESTERN
WISCONSIN...

...20Z Update...

In coordination with DVN/Quad Cities, IA; MKX/Milwaukee, WI;
ARX/LaCrosse, WI; and DMX/Des Moines, IA; and EAX/Pleasant Hill, MO
forecast offices, a Moderate Risk upgrade was introduced with this
update for far northern Missouri, much of eastern Iowa, southern
Wisconsin, and far northwestern Illinois. This area is very similar
to the Moderate Risk area from D2/Saturday, as the front forcing
all of the storms that will cause the flash flooding will be
ongoing across much of eastern Iowa Sunday morning, weaken during
the day, with more storms moving in from the west on Sunday night.
The storms are likely to develop along the same stalled out front
again Sunday night, but will extend well southwest of the
D2/Saturday period across much of northern Missouri and likely
eastern Kansas as well. The Moderate Risk was kept to mostly Iowa
for now since it will be a continuation of very heavy rainfall from
the D2/Saturday period. However, expect multiple inches of rain to
impact much of northern Missouri, including the Kansas City and St.
Joseph metros. Since relatively little rain is expected in those
metros on Saturday, the areas may take a round of storms before
soils are moistened up, but even there, training and multiple
rounds of storms are likely. Thus, while Kansas City and St. Joseph
are currently in a higher-end Slight, it's very possible the area
may need to be upgraded to a Moderate as well with future updates.
Regardless, the continuation of very heavy rain in already hard hit
areas will likely result in more impactful and widespread flooding
impacts across Iowa, far western Illinois, and far southwestern
Wisconsin on Sunday as compared with Saturday.

More widespread convection is also likely across much of Kansas and
into far eastern Colorado on Sunday. The storms are unlikely to
result in more flooding on Sunday since the storms on Saturday
should be relatively few and far between, but the area will be
monitored for potential need to upgrade to a Slight Risk, extending
from the current Slight across eastern Kansas.

The Marginals in the Southeast and Southwest were largely
unchanged. See the previous discussion below for more details on
those areas.

Wegman

...Previous Discussion...

...Southern Mid-Atlantic Coast to Northeastern Gulf Coast...

A lingering frontal boundary over northern Florida and high
pressure anchored over the northern Mid-Atlantic will maintain
low level southeasterly winds into the southeastern U.S. on Sunday.
Precipitable water values of 2.0 to 2.3 inches over the Southeast
and Florida will again support intense tropical downpours as
thunderstorms increase with daytime heating. Low level
southeasterly winds and confluent axes will combine with sea breeze
convergence and other mesoscale boundaries to support scattered
thunderstorms with isolated flash flood potential from 2-4 in/hr
rainfall rates.

...Southwest...

Continued advancing of the base of an upper trough from the central
Rockies into the central Plains and an elongated ridge over
California will favor northwesterly mid-level flow into the
Southwest. While this may reduce moisture availability across the
Four Corners region, low level southerly flow is expected to be in
place over the northern Gulf of California into Arizona, with
westerly flow advecting low to mid-level moisture downstream toward
New Mexico. Meanwhile, the front over the High Plains from
Saturday night is forecast to again sink down to the south with an
upslope flow regime setting up over northeastern New Mexico,
helping to increase low level moisture into the region. Moisture
values for much of central/southern Arizona and New Mexico are
expected to be near average and monsoon thunderstorms are expected
during the late afternoon and evening hours with perhaps greater
coverage than previous days. Typical potential for high short term
rain rates (1-2 inches in an hour or less) will set up with
isolated to widely scattered flash flood potential.

Otto

Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt