Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Tue Aug 12 2025 04:23:52

AWUS01 KWNH 120423
FFGMPD
MOZ000-ARZ000-TXZ000-OKZ000-121000-

Mesoscale Precipitation Discussion 0915
NWS Weather Prediction Center College Park MD
1222 AM EDT Tue Aug 12 2025

Areas affected...Eastern Oklahoma, Western Arkansas, far Northeast
Texas

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

Valid 120421Z - 121000Z

Summary...Slow moving showers and thunderstorms will continue to
pulse up along outflow boundaries and storm mergers overnight.
Rainfall rates of 2-3"/hr are expected, which could produce 1-2"
of rain in 30 minutes. Flash flooding is possible.

Discussion...The regional radar mosaic tonight shows an expansion
of convection across eastern Oklahoma into western Arkansas. This
convection is associated with multiple remnant outflow boundaries
that are clearly evident on radar, with convergence along these
boundaries leading to rapid updraft intensification to produce
dditional convective development. Estimated rainfall rates have
been as high as 2"/hr from KSRX, supported by rich thermodynamics
characterized by GPS measured PWs of 1.7 inches overlapping MUCAPE
of 1000-2000 J/kg. Additional ascent is being provided via slow
height falls downstream of a mid-level trough axis centered across
KS/OK.

The high-res CAMs are really struggling tonight with the current
activity, so their solutions must be used cautiously. However, an
ingredients based approach to the evolution combined with analysis
of current radar trends suggests that there can be several more
hours of slow moving storms before instability gets exhausted or
overturned. With PWs and MUCAPE remaining robust within the
pre-convective environment, any mergers/outflow collisions should
additionally result in thunderstorm growth, and a slow trend E/SE
in coverage is likely. 0-6km bulk shear across the region is
minimal at less than 20 kts, so storms should remain primarily of
the pulse variety. This suggests limited temporal duration of any
individual cell, but with chaotic motions driven primarily by
these small scale collisions thanks to weak 0-6km mean winds, some
places could receive multiple rounds of convection.

These thunderstorms will likely continue to produce rainfall rates
of 2-3"/hr (HREF probabilities for 2"/hr 15-30%), so even though
residence times will be limited, any storm may produce a quick
1-2" of rain in well under an hour. This will be sufficient to
cause rapid runoff despite elevated FFG, and a few instances of
flash flooding are possible overnight, especially across any more
sensitive or urban areas.

Weiss

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!-s5q1JYBL5Es53Nme6TuhNiAPPNOU4PEWEWjW23lwSk5tBH8v8aZ9_SFS7_0m6LPLipU=
9KTQQ1-3tQOnpMSJUz4lh2g$  for graphic product...

ATTN...WFO...FWD...LZK...OUN...SGF...SHV...TSA...

ATTN...RFC...FWR...ORN...TUA...NWC...

LAT...LON   37169302 36809253 35989236 34889240 34079276=20
            33419371 33009481 32799566 32759667 33079736=20
            33579774 34119777 34389725 34659630 35069559=20
            35709530 36779400=20

=3D =3D =3D
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