144
AWUS01 KWNH 261950
FFGMPD
GAZ000-TNZ000-ALZ000-MSZ000-LAZ000-MOZ000-ARZ000-TXZ000-OKZ000-270147-

Mesoscale Precipitation Discussion 1127
NWS Weather Prediction Center College Park MD
348 PM EDT Wed Aug 26 2026

Areas affected...Portions of the Lower Mississippi Valley into the
Southeast U.S.

Concerning...Heavy rainfall...Flash flooding possible

Valid 261947Z - 270147Z

Summary...Increasing threat of flash flooding over the next
several hours as thunderstorms initiate near and along the
proximity of a stationary front over the Southeast U.S. Rainfall
rates upwards of 2-3"/hr are possible in the strongest storms.

Discussion...Current radar and satellite depictions are beginning
to hint at the next round of heavy convective potential across the
Lower Mississippi Valley into the Southeast with sights on the
northern half of Mississippi and Alabama, extending back into
Arkansas. A very warm, moist airmass presence has allowed for a
very buoyant and favorable environment capable of producing some
significant thunderstorm genesis across the region as we step
through the latter half of the afternoon into the evening. At the
surface, a quasi-stationary front is analyzed across central AR
through northern MS and AL as of 18z with a slow southward
progression propelled by outflows stemming from a decaying complex
moving into the region from TN. Aloft, we have two distinct
disturbances that will work in tandem to provide more widespread
convective potential along the front, as well as the surrounding
areas encompassing parts of the Lower Mississippi Valley into the
Southeast. The first is noted with the decaying complex over the
Tennessee Valley pressing south into northern AL. Some strong
low-level convergence is analyzed via the latest RAP mesoanalysis
over the area just west of Huntsville allowing for a few stronger
cells to materialize and provide an isolated flash flood warning
over northwestern AL. The aided ascent coupled with outflows from
the complex to the north will maintain prevalence for more heavy
convective initiation over the next several hours with the
environment south of the front maintaining a significant 3000-4000
J/kg SBCAPE offering, more than capable for enhanced pulse
convection.

Further west into AR and MS, a well-defined CAPE gradient is
located from west to east over central AR into northern MS, noting
the gradient running right along the quasi-stationary front over
the area. Upstream into OK, another mid-level shortwave will
migrate east-southeast around the northeastern flank of a broad
ridge positioned over the Southern High Plains acting as a
suitable forcing mechanism for convective development this
afternoon and evening. Trends have favored a relatively slow
maturation of thunderstorm genesis for the next hour, but by
20-21z, anticipating a much larger coverage of thunderstorms to
materialize as the disturbance migrates closer to the region,
igniting storms along the CAPE gradient situated around the
stationary front. HRRR/RRFS combo have been consistent on this
signature of heavy convection developing over west-central AR with
a few strong cells also materializing over the Ozarks before
sinking southeast with the mean flow.

Rainfall rates in these cells will top between 2-3"/hr as regional
PWATs settle between 1.9-2.2" over the entire AR/MS/AL domain.
Heavy rainfall will allow for totals to enter the 2-4" range, with
a maxima of 6" plausible where cells train over the same area.
Relative storm motions will be fairly weak overall leading to the
threat for several inches of rainfall in a few hours time. Also
will be watching for potential cold pool mergers as noted via some
of the CAMs today, especially in proximity to the Mississippi
Delta where the signal has been present for multiple runs for
later this evening. This could benefit a larger areal footprint of
heavy rainfall with more thunderstorm development within the
convergent boundaries.

Kleebauer

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...BMX...FFC...HUN...JAN...LZK...MEG...MRX...PAH...
SGF...SHV...TSA...

ATTN...RFC...ALR...ORN...TUA...NWC...

LAT...LON   36759245 36639122 36239085 35669049 35209004
            34868923 34668867 34648802 34738730 35248625
            35008558 34188570 33558632 33238717 33148784
            33058877 32958987 32799096 32649250 32979424
            33919461 35039449 36079435 36639333