Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sat Jul 12 2025 20:37:36

AWUS01 KWNH 122037
FFGMPD
VAZ000-NCZ000-WVZ000-SCZ000-GAZ000-TNZ000-KYZ000-130135-

Mesoscale Precipitation Discussion 0661
NWS Weather Prediction Center College Park MD
435 PM EDT Sat Jul 12 2025

Areas affected...Portions of the Southern Appalachians

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

Valid 122035Z - 130135Z

SUMMARY...Locally slow-moving and anchored thunderstorms near
areas of steep and rugged terrain may cause at least isolated
areas of flash flooding going into the evening hours.

DISCUSSION...The afternoon GOES-E IR satellite imagery shows
cooling convective tops continuing across portions of the southern
Appalachians including far eastern TN, southwest VA, western NC,
upstate SC, and northern GA. This is in association with
relatively slow-moving areas of heavy showers and thunderstorms
which are being focused predominantly by orographic ascent/upslope
flow near the higher terrain along with differential heating
boundaries adjacent to it. However, there is also some very modest
shortwave energy approaching from the TN Valley which is also
acting as a catalyst for convective initiation and expansion of
cells.

MLCAPE values are as high as 1500 to 2500 J/kg, with PWs that are
just slightly anomalous for this time of the year at about 1.5 to
1.75 inches. Very little shear is in place, so the convective mode
is mostly pulse, but the cell-motions are quite weak, and this has
been allowing for some cells to produce hourly rainfall amounts of
1.5 to 2.5 inches.

These higher rainfall rates along with some recent trends for
cells to become anchored near some of the higher terrain suggest
the potential for some storm totals to reach 3 to 4+ inches over
the next several hours, and this supported by some of the 12Z
HREF/REFS guidance.

These rains will be falling over areas of steep and rugged
terrain, and as a result will be capable of producing a threat of
at least isolated areas of flash flooding going into the evening
hours.

Orrison

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!4aZ64bTjjTloGwKLCWFpmpdNfGmYA2VgkYANaQQkPwn5IvO6ra8ymrhKv2aIv2TfNT1q=
LOADLgbcFhoL7osl83Nr7I4$  for graphic product...

ATTN...WFO...FFC...GSP...JKL...MRX...RAH...RLX...RNK...

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

LAT...LON   37658120 37348028 36558018 35678060 34358206=20
            33938313 33938429 34218461 34678446 35288400=20
            36188337 37138284 37568209=20

=3D =3D =3D
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