Mesoscale Precipitation Discussion 0904
NWS Weather Prediction Center College Park MD
612 PM EDT Thu Sep 27 2018

Areas affected...Central Appalachians

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

Valid 272211Z - 280341Z

Summary...Steady moderate to locally heavy rain through this
evening across the central Appalachians, where wet antecedent
conditions are in place, may lead to flash flooding.

Discussion...Latest water vapor imagery showed a strong mid-level
shortwave trough tracking across western Kentucky into southern
Indiana. A surface low was analyzed across far eastern Kentucky
with a stationary boundary draped across southern Virginia.
Regional radars from around the area depict widespread moderate to
locally heavy rainfall occurring from West Virginia into portions
of VA, western/central NC, eastern KY/TN.

Latest RAP mesoanalysis shows instability has built northward into
far southwest VA with MLCAPE values of 500 J/kg (upwards to 1000
J/kg across eastern TN/western NC). In an impressive plume of
highly anomalous moisture (PWATs 1.8 to 2.0") ahead of a slowly
moving cold front, there is an axis of 850 mb moisture transport
along the spine of the Appalachians.

Threat of heavy rain/flash flooding over the next 3-6 hours will
be focused on far eastern KY, southwest VA, portions of southern
WV as well as portions of eastern TN/western NC where clusters and
broken lines of storms will converge. Recent rain rates from
JKL/MRX show rates of 0.5-1.0 in/hr. Recent runs of the HRRR and
WRF-ARW show this activity moving into portions of southwest VA
and southern WV through 03-04z. Additional rainfall amounts of 1-2
inches (locally higher amounts) appear likely across portions of
the area, especially across southwest VA into southern WV.

Given very wet antecedent conditions in places (locations 300-600
percent of normal rainfall last 7 days)and low FFG values, flash
flooding will be possible through the evening hours.

Taylor

ATTN...WFO...GSP...JKL...LWX...MRX...RLX...RNK...

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

LAT...LON   38498023 38057940 37207897 36548034 35838117
            35488179 35358252 35288326 35378377 35888392
            36778373 37088353 37688261 37688262 38058190
            38378141