FOUS30 KWBC 030803
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
403 AM EDT Fri Apr 3 2026

Day 1
Valid 12Z Fri Apr 03 2026 - 12Z Sat Apr 04 2026

...THERE IS SLIGHT RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTHERN PLAINS INTO THE OZARKS, MISSOURI VALLEY, AND UPPER
MISSISSIPPI VALLEY...

At the mid-levels, a stout wave over the Intermountain West
(centered over Wyoming) will migrate eastward throughout the day,
spreading increasingly strong mid-level flow and height falls from
the High Plains eastward toward the Mid/Upper Mississippi Valley.
At the surface, strong 850mb flow and poleward flux of
moisture/instability will become established along and ahead of a
low initially across the Kansas/Nebraska border region at the
beginning of the forecast period and persist through 12Z Sat. Late
in the forecast period, a cold front will migrate southward across
the southern Plains. Areas of scattered thunderstorms are expected
along and ahead the front and low especially during the afternoon
and evening, with several areas of flash flooding expected.

The primary area for flash flood potential will exist along the
OK/TX Red River vicinity southward toward central Texas and the Big
Country. Scattered thunderstorms are expected to develop during
the afternoon and evening across the region, with CAMs suggestive
of training/repeating behavior and local areas of 2-5 inch totals.
The glancing influence of the aforementioned mid-level wave across
the region lends some doubt on degree and location of
daytime/afternoon convective coverage, which should modulate the
flash flood risk substantially.

Even if convection materializes as depicted by CAMs, antecedent
dryness of ground conditions are a mitigating factor for a more
widespread or significant flash flood risk. Persistent training
will likely be needed for ground conditions to lose receptiveness
to rainfall on a widespread basis. Both pre-frontal convection and
convection moving in along a surface cold front late represent two
distinct regimes for heavy rain and flash flood potential - with
that risk eventually spreading toward I-35 in Texas and the DFW
Metroplex area through early Saturday.

Farther north, convection along the front will likely sweep through
portions of Missouri and Oklahoma, with a greater risk/potential
for multiple mergers and/or convective clusters with southward
extent. Areas just southeast of Kansas City received copious
amounts of rain Thursday and will probably not have fully recovered
before the incoming thunderstorm threat through early Saturday,
necessitating maintenance of Slight Risk probabilities there.

Lastly, models (primarily CAMs) depict potential for
repeating/training convection across portions of northeastern Iowa
and vicinity through much of the day (from 16-18Z through well into
the evening) along/near a surface warm front and well ahead of an
eastward-moving cold front that should reach the area late in the
forecast period. NASA Sport soil moistures suggests slightly more
moist ground conditions in these areas, and the advance of the
mid-level wave and confluence on the northern end of strong 850mb
flow all point to prolonged deep convective potential. 3-5 inch
totals cannot be ruled out in this regime. A Slight Risk has been
added to the outlook in these areas as a result.

Though less widespread, additional convection should traverse wet
ground conditions across portions of Ohio, Pennsylvania, and
southern New York State, supporting continued Marginal
probabilities in that area.

Cook

Day 2
Valid 12Z Sat Apr 04 2026 - 12Z Sun Apr 05 2026

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FROM THE CENTRAL
AND EASTERN GREAT LAKES SOUTHWESTWARD TO CENTRAL TEXAS AND THE
LOWER MISSISSIPPI RIVER VALLEY...

Much of convective evolution during the D2/Sat forecast period will
depend on convective details from lingering convection across
Arkansas and Texas left over from D1/Fri. East-northeastward
progression of a mid-level wave toward the Great Lakes will aid in
southeastward movement of a cold front from the Plains through the
Ozarks/Mid-Mississippi Valley during the forecast period. This
front will gradually become more parallel to weakening flow aloft
from Texas to Mississippi, supporting additional opportunities for
training convection as storms organize along remnant outflows and
backbuild. This regime suggests that pockets of 1-3 inch rainfall
totals are likely especially from central Texas to northern
Alabama, with heavier totals also possible from central Mississippi
south into southeastern Louisiana as well. While Slight Risk
potential exists with this setup, concerns about 1) uncertainty of
prior-day convective evolution and 2) antecedent dryness continue
to be limiting factors for a more widespread flash flood risk at
this time.

Farther north, convection is likely to be progressive across much
of the Lower Ohio Valley along with potential for inhibited
destabilization due to more widespread convection across the Lower
Mississippi Valley. Too much uncertainty exists to reduce the
Marginal Risk area at this time. Notable exceptions to this general
regime exist, however, from northern Ohio into southern New York
State and Pennsylvania, where models suggest appreciable daytime
heating and moderate instability developing. Storms may not be all
that fast moving either in Pennsylvania as that region should
reside on the southern extent of stronger mid-level flow into
southeastern Canada. Convective coverage is a bit uncertain, but
any greater-than-anticipated coverage of convection in this
environment could locally raise flash flood concerns - especially
with low FFGs noted across that area.

Cook


Day 3
Valid 12Z Sun Apr 05 2026 - 12Z Mon Apr 06 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
SOUTH TEXAS ON SUNDAY...

Maintained the Marginal Risk of Excessive rainfall area that was
introduced by the WPC Medium Range desk as a west-to-east oriented
front makes its way southward. Deeper moisture should e pooling
along and south of the boundary with precipitable water values
around 1.75 inches in place at the start of the outlook period.

Given uncertainties detailed n the Day 2 period with respect to the
timing and placement...combined with the 03/00Z NCEP global models
now showing the front to be more progressive than in earlier runs
which led to CAPE being swept out of South Texas faster...was not
inclined to introduce a Slight Risk area at this point. At the same
point...spaghetti plots from the non-CAM ensembles still show
enough members with 1 inch QPF and a few contours of 2 inch QPF to
support keeping the Marginal area with only minor nudges around the
periphery.

Bann


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