Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sat Aug 23 2025 21:03:02

AWUS01 KWNH 232102
FFGMPD
VAZ000-NCZ000-WVZ000-GAZ000-TNZ000-KYZ000-ALZ000-240300-

Mesoscale Precipitation Discussion 0987
NWS Weather Prediction Center College Park MD
501 PM EDT Sat Aug 23 2025

Areas affected...TN Valley...Southern Appalachians

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

Valid 232100Z - 240300Z

SUMMARY...Scattered slow-moving areas of showers and thunderstorms
may pose an isolated threat for flash flooding going through this
evening.

DISCUSSION...The late-afternoon GOES-E GeoColor satellite imagery
shows scattered areas of showers and thunderstorms impacting
portions of the TN Valley and the southern Appalachians with an
emphasis on the Cumberland Plateau.

Moderate buoyancy with MLCAPE values of near 1500 J/kg coupled
with modest moisture convergence near the terrain should help
sustain the convective threat through early this evening. PWs are
seasonably moist with values of 1.5 to 1.75 inches and this
coupled with the available instability will support rainfall rates
reaching as high as 1.5 to 2.5 inches/hour with the stronger
storms.

Overall, a lack of shear should keep the convection in pulse mode
through the remainder of the afternoon and evening. However, with
weak steering currents and the orographic focus of the activity
near areas of higher terrain, there may be sufficient persistence
of convection locally to yield some spotty rainfall totals of 2 to
4 inches.

The FFG values across portions of far southwest VA down through
eastern TN are relatively low, and the 12Z HREF/06Z REFS suite of
guidance shows some low to moderate probabilities (20 to 50
percent) of seeing the 3-hour FFG values exceeded going through
this evening. This suggests a threat for isolated areas of flash
flooding with these pulse areas of convection.

Orrison

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!_fDX79rI7xtOdKs1du2XA6IQ6eBLAMkKpP7Y6Bvjs91vWQLp5-aGgT2C6nkbskQp6VRs=
ZzhsJ3Hn_Xs9PTNu2Q3ATGs$  for graphic product...

ATTN...WFO...BMX...FFC...GSP...HUN...JKL...LMK...MRX...OHX...
RLX...RNK...

ATTN...RFC...ALR...ORN...TIR...NWC...

LAT...LON   38328199 38218097 37628098 36628167 36028248=20
            35288382 35068463 34978543 34618589 33938660=20
            34108758 35018756 35738685 37138449=20

=3D =3D =3D
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