Mesoscale Precipitation Discussion 0568
NWS Weather Prediction Center College Park MD
209 PM EDT Tue Jul 31 2018

Areas affected...Central Appalachians

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

Valid 311807Z - 312330Z

Summary...Thunderstorms were continuing to develop across the
central Appalachians. These storms were beginning to reach areas
that have received moderate to heavy rainfall in the past 24
hours, and thus may be more prone to flooding. Rain rates could
reach 1-2 in/hr, with flash flooding possible, from southwest
Pennsylvania, into West Virginia, and then the mountains of
western Virginia and northwestern North Carolina.

Discussion...Regional radars showed several lines and clusters of
thunderstorms continuing to develop across the central
Appalachians region. These storms were generally increasing in
coverage and intensity per GOES-16 IR channel trends (cooling
cloud tops) and increasing lightning activity. The convection was
just beginning to advance into areas of reduced FFG (for 3hr,
generally less than 2 inches). Although these values may not be
perfectly representative for every basin, they do indicate an
overall trend for strengthening convection moving into areas that
may be more flood prone.

Although some of the convective lines were oriented roughly
parallel to the 850-300mb mean wind, they were also slowly
advancing east, which may reduce the potential for lengthy periods
of training. Nevertheless, some potential for brief training does
exist, and given the reduced FFG even 1-2 in/hr rain rates could
lead to flash flooding. The environment with moderate instability
(1000 j/kg MLCAPE) and elevated moisture (PW around 1.7-1.8
inches) should support rain rates this high, and they have been
estimated to be that high in localized bands from MRMS and WSR-88D
dual pol rainfall.

Therefore, confidence is not high in a specific, concentrated area
of flash flood potential given a lack of focused training or
backbuilding. However, the rain rates and antecedent conditions
should create the potential of some localized flash flooding this
afternoon in the central Appalachians.

Lamers

ATTN...WFO...CTP...GSP...JKL...LWX...MRX...PBZ...RAH...RLX...
RNK...

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

LAT...LON   40737878 39747847 38957922 38197999 37588053
            37028010 36158024 35868151 35718221 36618192
            37398212 38018236 38788193 39818100 40618012