Mesoscale Precipitation Discussion 0903
NWS Weather Prediction Center College Park MD
114 PM EDT Thu Sep 27 2018

Areas affected...Southern/Central Appalachians

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

Valid 271713Z - 272243Z

Summary...Widespread showers and storms moving into very saturated
and sensitive areas through the afternoon may lead to flash
flooding across the southern and central Appalachians.

Discussion...Latest water vapor imagery showed a strong shortwave
trough across northeast Arkansas lifting northeast. Broad
southwesterly flow ahead of it has pumped anomalously high
moisture across the southern and central Appalachian region (PWATs
1.8 to 1.9 inches or 2.5-3.0 SD above normal). Instability axis
lies across eastern TN/far southwestern NC and southward.

Through this afternoon, the environment should become increasingly
more favorable for widespread showers and thunderstorms from far
northern GA into eastern TN/western NC and into southeast
KY/southwest VA. RAP forecasts through 21z show more favorable
upper level divergence developing coincident with pockets of
1000-2000 MLCAPE.

Latest runs of the HRRR show clusters of storms converging across
the region through late this afternoon and should be capable of
producing intense rainfall rates of 1 to locally 2 inches/hour.
27.12z HREF mean shows widespread 1-1.5 inches and locally higher
amounts appear likely in convective clusters.

The area is well saturated with previous 7 days rainfall running
400 to 600 percent of normal across eastern TN/KY into southwest
WV/VA. Much of the area's 1-hr FFG is 1-1.5 inches or lower.

As a result, with showers/storms expected to move into the area,
flash flooding will be possible. 

Taylor

ATTN...WFO...BMX...FFC...GSP...HUN...JKL...MRX...OHX...RLX...
RNK...

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

LAT...LON   36488462
37608122 37388061 37018037 36148114 34948264
            34478364 34048504 33928548 34108579 34888576
            35338562 35748544 36438506 36858473 37168412
            37218339 37438257 37538184