Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sat Sep 27 2025 05:57:12

AWUS01 KWNH 270556
FFGMPD
VAZ000-NCZ000-WVZ000-271200-

Mesoscale Precipitation Discussion 1144
NWS Weather Prediction Center College Park MD
156 AM EDT Sat Sep 27 2025

Areas affected...much of southern and central VA...portions of
northwestern NC and southeastern WV

Concerning...Heavy rainfall...Flash flooding likely

Valid 270600Z - 271200Z

Summary...Training banded heavy rain with 1-2"/hr rates expected
to result in additional rainfall totals of 3-5" through 8 AM.
Isolated to scattered instances of flash flooding are likely.

Discussion...Disorganized showers and thunderstorms across
southern portions of the Mid-Atlantic have consolidated into a
defined band of heavy rainfall over the past couple of hours. This
band extends a couple hundred miles across southern VA into
northwestern NC, paralleling a surface/low-level frontal boundary
and associated moisture gradient (PWs ranging from 1.5-2.0" across
the gradient, nearing the climatological max moving average at
GSO/RNK). MUCAPE of 500-1000 J/kg is sufficient to sustain deep
convection, and strong upper-level dynamics (right-entrance region
of a jet streak with DPVA via shortwave trough/PV anomaly
upstream) along with modest easterly low-level moisture transport
could allow for localized training of 1-2"/hr rainfall rates.

While hi-res models overall have poorly handled the convective
organization since 00z, the latest HREF suite still indicates
relatively high odds (20-40%) for localized 3" exceedance through
12z (per 40-km neighborhood exceedance probabilities). Given that
banded heavy rainfall has already reached a level of organization
beyond model depictions, these probabilities could be underdone.
Expect that training of banded heavy rainfall lead to additional
rainfall totals of 3-5" with corresponding 3-6 hour Flash Flood
Guidance (FFGs) generally ranging from 1.5-3.0" (with portions of
northwestern NC having already received localized totals of 2-3"
from prior rainfall over the past 3-6 hours). Isolated to
scattered instances of flash flooding are likely.

Churchill

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!-NEApKCJ4uPZO6DNJvFdxLGh9mWJaAOPtC9jNS0cpZKIgR3AfLtk4rCXduNNT3xAGa0P=
jlzh2eNDBfDORe_QvkbnLnY$  for graphic product...

ATTN...WFO...AKQ...GSP...LWX...RAH...RNK...

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

LAT...LON   38038048 37947951 37637883 37567808 37377714=20
            37147680 36607710 36637809 36697890 36297952=20
            35957992 35768021 35708054 35798087 35998103=20
            36448113 36898090 37378079=20

=3D =3D =3D
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