AWUS01 KWNH 270234
FFGMPD
VAZ000-NCZ000-SCZ000-GAZ000-TNZ000-270830-

Mesoscale Precipitation Discussion 1071
NWS Weather Prediction Center College Park MD
1034 PM EDT Thu Sep 26 2024

Areas affected...northeastern GA into the western Carolinas and
southwestern VA

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

Valid 270230Z - 270830Z

Summary...Additional 1-3 inch rainfall totals, with localized 3-5
inches into the Blue Ridge Mountains, are expected through 08Z
across GA/SC/NC. Flash flooding is ongoing and will only worsen
and expand with time.

Discussion...Regional radar imagery from 0215Z showed widespread
rain across much of the southeastern U.S. but with gaps over
portions of SC in advance of an outer rain band from Helene
tracking across the southeastern SC/GA border. A combination of
MRMS and gauge reports showed peak rainfall rates ranging between
0.5 to 1.5 in/hr across the upslope favored terrain of the
southern Appalachians, specifically the Blue Ridge Mountains.

Instability remains low in the vicinity of the terrain, less than
250 J/kg (via 02Z SPC mesoanalysis data), increasing to over 1000
J/kg near the SC/GA coast. However, strong forcing, including
30-40 kt of southeasterly 925-850 mb winds (via KGSP and TCLT VAD
wind data) was favorably oriented into the mountains, beneath
divergent and diffluent flow aloft to the east of a closed low
over southeastern MO and in advance of Hurricane Helene.

No major changes to the current setup are expected through 08Z
with the core of Helene perhaps just getting into the southern
portions of the MPD threat area around 08Z. However, some increase
in instability across inland is anticipated as Helene tracks
northward overnight and an increase in the 925-850 mb wind into
the 50-70 kt range overspreads the region. Rainfall rates of 0.5
to 1.5 in/hr at times will continue with an additional 1-3 inches
for many areas from northeastern GA into central and western SC/NC
with locally 3 to 5 inch additional totals for the terrain.

These rains will continue to make for an extremely dangerous
situation later tonight as the core of Helene's rainfall arrives
later this morning, for which another MPD will be issued.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!8507ghn4_OfQ0msZxABfsw7hon-pAhQj4dJCRsRRojdNrckPRvz-ZJgfoZjuT2HuVaWq=
zTeXznXhxMAZ7LnLrC83l1s$  for graphic product...

ATTN...WFO...CAE...CHS...FFC...GSP...MRX...RNK...

ATTN...RFC...LMRFC...OHRFC...SERFC...NWC...

LAT...LON   36968025 36658015 36228066 34778055 33538070=20
            32718117 32598203 32798287 33448393 34458474=20
            35228414 36048240 36758121=20

=3D =3D =3D
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