FOUS30 KWBC 240750
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
350 AM EDT Fri Apr 24 2026

Day 1
Valid 12Z Fri Apr 24 2026 - 12Z Sat Apr 25 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL IN THE MID SOUTH...

A convective line that had stalled over northern Oklahoma between
02Z and 06Z has recently shown signs of slow forward progress. This
increases confidence in the general evolution depicted in the 00Z
hi-res model guidance suite, which shows the line reaching northern
Arkansas and east-central Oklahoma by the start of the forecast
period at 12Z Friday, and continuing southeast through much of
central and eastern Arkansas through the daytime hours.

The end result should be an increasingly stable air mass and
widespread cloud cover over those same portions of Arkansas, and=20
adjacent southern Missouri and western Tennessee, associated with=20
gradually decaying convection, a cold pool and surface meso-high.=20
For these reasons, and trends to the southwest with the heaviest=20
precipitation in both hi-res and AI guidance, the Marginal Risk has
been shifted likewise. A reinvigoration of convection in the=20
afternoon and evening is most likely on the upshear flank of the=20
cold pool with west-southwesterly low level inflow and an upstream=20
reservoir of strong instability. The potential exists for periods=20
of training convection along and near the existing outflow boundary
(likely on the order of 1-3 hours), which may provide=20
opportunities for localized corridors of heavy rainfall with 1-2=20
inch per hour rain rates, and resulting flash flooding. The precise
placement remains somewhat uncertain, so the Marginal Risk remains
relatively broad to account for a variety of scenarios. In
particular, the risk area was fanned out a bit more to the north
and west than deterministic WPC QPF would imply, because of the
relatively slow pace of the ongoing convection and the very common
northeast placement bias in this sort of mesoscale setup respectively.

Lamers


Day 2
Valid 12Z Sat Apr 25 2026 - 12Z Sun Apr 26 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE ARKLATEX
REGION INTO EASTERN OKLAHOMA AND SOUTHEAST KANSAS...

It seems likely that scattered thunderstorms will develop on
Saturday afternoon in a corridor of strong instability across the
Southern Plains. However, there remains considerable uncertainty as
to the position of surface boundaries and the northward extent of
the strongest instability. Despite model guidance depicting a
variety of mesoscale scenarios, most models do show organized
convective clusters pushing southeast along the 1000-500mb
thickness gradient into the evening and overnight hours. This
motion could allow for some training and areas of locally heavy
rainfall; the strong instability and PWs of 1.2 to 1.5 inches would
support 1-2 inch per hour rain rates. If those rain rates can be
sustained for a couple hours, localized flash flooding would be
possible. For now the Marginal Risk was maintained as model
guidance does not really show any extended duration of training at
this point, and there is not enough model agreement to identify a
preferred corridor for heavy rainfall.

Lamers


Day 3
Valid 12Z Sun Apr 26 2026 - 12Z Mon Apr 27 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL IN THE CENTRAL
PLAINS AND OZARKS...

Strong cyclogenesis in the central Plains on Sunday will facilitate
significant northward moisture transport and a more expansive area
of thunderstorm activity stretching from the Dakotas south toward
Arkansas. The stronger signal for heavy rain exists further north
where stronger synoptic forcing and mid-upper level height falls
will be focused. However, instability is expected to be more
limited in those areas. Nevertheless, the combination of moderate
instability with PWs exceeding 1 inch and potential for more
persistence of rain and thunderstorms could yield localized flash
flooding. Further south, stronger instability could support higher
rain rates, but weaker forcing overall may keep convection
scattered and reduce opportunities for training and focused
corridors of heavy rainfall. Some portions of Kansas, Missouri,
Oklahoma, and Arkansas will likely have experienced substantial
rainfall in the preceding several days, and so may be more prone to
runoff issues if organized thunderstorms are more persistent. The
expected tradeoffs between convective coverage and available
instability, with respect to the overall flash flood threat, only
merit a broad Marginal Risk at this time.

Lamers
$$
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 * Origin: Project Scorpio TEST (618:250/6)