643
AWUS01 KWNH 242230
FFGMPD
VAZ000-NCZ000-WVZ000-SCZ000-250415-

Mesoscale Precipitation Discussion 1049
NWS Weather Prediction Center College Park MD
629 PM EDT Tue Sep 24 2024

Areas affected...Southwestern Virginia and West-Central North
Carolina into Upstate South Carolina

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

Valid 242227Z - 250415Z

SUMMARY...Increasing coverage of thunderstorms focusing over a
stationary front near the NC/VA border brings the risk for quick 2
to 4" rainfall and scattered flash flooding into this overnight.

DISCUSSION...Thunderstorms, some of which are supercells, will
continue to develop in a warm sector in southwest VA and western
NC and further develop as they cross a stationary front/cold air
damming wedge and into south-central VA and central NC. Recent
rainfall estimates of 2.5"/hr are near Martinsburg, VA which is
just beyond the stationary front. High moisture (PW 1.8 to 2.0")
and instability (MLCAPE 1500 to 2500 J/kg) are allowing this heavy
development in the warm sector which convergence and a sharp
downward gradient over the front slowing activity that crosses it.
SWly low level flow is 15 to 20 kt which will keep
moisture/instability advection over the front and allow further
development.

Confidence has increased in the flash flood potential along the
front with recent HRRRs/18Z NAMnest all featuring QPF of 2 to 4"
before midnight along the west-central NC/VA border and into
south-central VA. Stability well into the cold sector behind the
front should continue to limit the progression of activity to a
couple counties into south-central VA with ongoing activity
expected west of the Blue Ridge to the Alleghenies of VA. Further
development is likely down the eastern side of the Appalachians
tonight, so the outlook area include western NC into Upstate SC
given earlier heavy activity there today. Previous flooding in the
Raleigh-Durham Triangle makes them vulnerable and the presence of
the front through there should allow for further flooding
concerns. All to say flash flooding is likely through this evening
near the frontal zone and better characterized as possible farther
south over western NC into SC.


Jackson

...Please see www.wpc.ncep.noaa.gov for graphic product...

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

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

LAT...LON   37777959 37167911 36807809 36187811 35817869
            35247959 35448056 35428136 34988224 35398278
            35998190 36638133 37048113 37418058 37728013