AWUS01 KWNH 260552
FFGMPD
VAZ000-WVZ000-261030-

Mesoscale Precipitation Discussion 1061
NWS Weather Prediction Center College Park MD
152 AM EDT Thu Sep 26 2024

Areas affected...eastern WV into central VA

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

Valid 260548Z - 261030Z

SUMMARY...A few areas of training will maintain a flash flood over
the next 3-4 hours, but decreasing instability is expected to
diminish the threat by 10Z. Peak rainfall rates of 1 to 1.5 in/hr
are expected.

DISCUSSION...Scattered showers and thunderstorms remained as of
0530Z across central/western VA into eastern WV. MRMS-derived
rainfall rates over the past 2 hours have been peaking in the 1 to
1.5 in/hr range, mainly near areas of mesoscale rotation. Cells
were being driven along the leading edge of moisture
transport/warm air advection along an anomalous moisture plume
extending well northward of Hurricane Helene located in the
southern Gulf of Mexico. Low level upslope flow was also a factor
with 20-30 kt of 925-850 mb oriented from the SSE, focused into
the Blue Ridge and Appalachians Mountains, located beneath
diffluent flow aloft to the east of an upper low positioned over
the Lower OH Valley.

A few factors are expected to influence flash flood potential over
the next few hours. While a few pockets of south to north training
and repeating are ongoing from eastern WV into western and central
VA, instability has been...and will continue to fall...through the
remainder of the night. A low level anticyclone off of the central
Mid-Atlantic coast is forecast to shift eastward which should
allow for veering of the low level flow in VA, with winds becoming
oriented more parallel to the axis of terrain. While precipitable
water values will remain high (1.5 to 2.5 standard deviations
above the mean) and highly localized instances of higher rain
rates may remain by 10Z, the overall threat is expected to
diminish later this morning.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!_2MzV1xwHkH74tyNhg-PRtf5AHCekb-1piLPcB9LunPN8SIIowq52t5W8RXcl3h8N5FG=
AGIUlQs6EECw3Ti_eoZE5Zc$  for graphic product...

ATTN...WFO...LWX...PBZ...RLX...RNK...

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

LAT...LON   39317873 38997788 38317828 37597878 37447924=20
            37437971 37478029 37738058 38018053 38398036=20
            38797995 39177930=20

=3D =3D =3D
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