FOUS30 KWBC 220757
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
357 AM EDT Wed Apr 22 2026

Day 1
Valid 12Z Wed Apr 22 2026 - 12Z Thu Apr 23 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHEAST TEXAS AND SOUTHWESTERN LOUISIANA...

Steady southerly flow off the Gulf will continue to advect a plume
of Gulf moisture northward across the Marginal Risk area. The flow
will not be much to write home about, generally between 5-15 kts=20
at 850 mb. In addition to the rather weak advection the upper=20
levels will become decidedly less favorable for widespread rain=20
across the region as ridging and associated subsidence build in.=20
Thus, there is good agreement that any heavy rains will be=20
disorganized and widely scattered in nature, as compared with the=20
rains further west across Texas the past couple days. Urban=20
concerns remain a driving factor for maintaining the Marginal.
Guidance has shifted a bit to the south and west with the threat
for a few cells capable of heavy rains. This resulted in the
Marginal being shifted west along I-10, over an area that has been
hard-hit with heavy rains in recent days. Meanwhile portions of the
Piney Woods of far eastern Texas were removed as guidance has
suggested any more organized cells will be confined to around the
I-10 corridor. The westward shift resulted in small trimming in
south-central Louisiana as well. Should there be greater than
expected organization from Houston west along I-10, a targeted
Slight Risk may need to be considered due to the saturated soils
from yesterday's and prior days' rainfall.

Wegman


Day 2
Valid 12Z Thu Apr 23 2026 - 12Z Fri Apr 24 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM NORTHEASTERN
OKLAHOMA THROUGH THE ARROWHEAD OF MINNESOTA...

A strong but slow-moving low will lurk north of North Dakota in
southern Manitoba Thursday and Thursday night. The leading cold
front associated with this low has consequently also slowed down
its forward speed in much of the guidance. The result has been an
increase in forecasted rainfall that will occur ahead of that cold
front as it uplifts a moist and unstable air mass with a 30-50 kt
LLJ. Since the front has slowed down, there's more time for
moisture to advect north with the LLJ into Iowa, Minnesota, and
Wisconsin. While portions of Minnesota and Wisconsin were hard hit
with heavy rains last week, there has been sufficient time for the
soils to dry out some and for the rivers to drain that rainfall.
Thus, conditions are at or even a bit below normal for soil
moisture. Despite that, potential for fast-moving but training
storms could still result in some "stripes" of heavier rainfall
that could cause isolated flash flooding, especially if urban
centers such as the Twin Cities are included. The inherited
Marginal was shifted west but expanded well to the north to include
some of these more vulnerable areas of Minnesota and Wisconsin with
this update. The good news is further south across Kansas and
Missouri, the forcing now doesn't look like it will be quite as
strong as the forecast looked 24 hours ago. Thus, while a Slight
Risk upgrade was considered for along the KS/MO border south of
Kansas City yesterday, confidence has increased that the current
Marginal Risk for that area will suffice.

Wegman


Day 3
Valid 12Z Fri Apr 24 2026 - 12Z Sat Apr 25 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE MIDDLE AND LOWER MISSISSIPPI VALLEY...

A slow-moving cold front will run into increasing Gulf moisture and
instability across the Middle and Lower Mississippi Valley on
Friday. Clusters of showers and thunderstorms will develop along
the front in northwestern portions of the Marginal across Arkansas
and southeastern Missouri with peak heating Friday afternoon. Those
storms will gradually progress south and east, with the potential
for localized training of stronger cells embedded within these
clusters of storms. Almost all of the Marginal Risk area is in an
area with extremely dry soils. Depending on the soil type, this
could make some of the soils (clays) start out the rainfall event
in a very hydrophobic state, which would support rapid runoff.
However, for most, all but the heaviest rains will be very
beneficial for this parched area of the country. Urban areas, areas
with hydrophobic soils, and poor-drainage areas will be at the
greatest risk for isolated instances of flash flooding. Smaller=20
drainage basins and the portions of Arkansas with the Ozarks=20
topographically confining any potential runoff to steep valleys
will also be at a locally higher risk for flash flooding.

Wegman
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