FOUS30 KWBC 170746
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
346 AM EDT Fri Apr 17 2026

Day 1
Valid 12Z Fri Apr 17 2026 - 12Z Sat Apr 18 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM OKLAHOMA
THROUGH PORTIONS OF THE MIDWEST...

A strong cold front tracking southeast across the Plains will run
into a moist and unstable air mass driven by a robust low level jet
streaming north off the western Gulf and into the Great Lakes.
Meanwhile, a strengthening upper level jet will develop across
Texas and Oklahoma Friday night that will further enhance lift
across the Slight Risk region, particularly the southern part of
it. The result will be a series of waves of strong thunderstorms
that will feed on the influx of moisture and instability to allow
for frequent redevelopment and training as the entire complex of
storms pushes southeast. The strongest storms and most persistent
rainfall will occur over areas hard-hit in recent days with prior
heavy rainfall, so soils in areas from southern Oklahoma to western
Missouri are already near saturation and well above normal for soil
moisture content for this time of year. Urban areas from Kansas
City to Tulsa will be especially vulnerable should persistent heavy
rains set up over those metro areas. Meanwhile, a portion of the
Ozarks could also introduce a topographic factor to any flooding
potential. A higher-end Slight (25-40% chance of flash flooding)
is in effect from northwestern Oklahoma through central Missouri.

Meanwhile, further north into the Midwest, the storms are more
likely to organize into a single line of storms more quickly.
However, these areas have even more saturated soils due to more
recent rains. When added the urban factor in cities such as St.
Louis, Chicago, and Milwaukee, even a shortened period of heavy
rainfall could still result in widely scattered instances of flash
flooding. The Slight Risk in this area was expanded north up Lake
Michigan to Green Bay, but elsewhere remains little changed.

Wegman


Day 2
Valid 12Z Sat Apr 18 2026 - 12Z Sun Apr 19 2026

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

A strong cold front sweeping south down the Plains will provide the
primary forcing for a line of strong thunderstorms to form as the
front uplifts a warm and moisture-laden air mass from the Gulf. Due
to close proximity to the Gulf, PWATs are likely to spike to
between 1.5 and 1.75 inches Saturday evening. This will support
thunderstorms capable of very heavy rainfall. The line will
generally be progressive, moving south. Further, the Marginal Risk
area is generally covering some of the highest FFG areas in the
country. Thus, the flash flooding threat is largely focused on the
urban factor in areas such as Houston, Beaumont, and Alexandria.
Most of the convective activity is expected at or after sunset, so
any flooding that occurs will be more dangerous.

Wegman


Day 3
Valid 12Z Sun Apr 19 2026 - 12Z Mon Apr 20 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR DEEP SOUTH
TEXAS...

An area of disturbed weather, partially from the remnants of a cold
front that swept across much of Texas on Saturday, will impact
portions of Deep South Texas Sunday into Sunday night. The air mass
will be characterized by summer-like amounts of moisture, with
PWATs exceeding 2 inches in a few areas, and over 1.75 inches
across much of Deep South Texas. This will support any showers and
thunderstorms that form across the area to be capable of very
heavy rainfall. However, the forcing for this rainfall will be
lacking, resulting in only isolated to widely scattered showers and
thunderstorms. Further, the FFGs in Deep South Texas are quite
high, so any storms, which should be slow-moving, would need to
train or remain over a single area for a while to produce flash
flooding. Thus, only isolated instances of flash flooding are expected.

Wegman
$$
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