Mesoscale Precipitation Discussion 0564
NWS Weather Prediction Center College Park MD
328 PM EDT Mon Jul 30 2018

Areas affected...Enter areas affected

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

Valid 301927Z - 302127Z

Summary...A small but well formed MCS may continue to pose a short
term flash flood threat as it moves into very saturated portions
of the Mid-Atlantic states. Weakening is expected toward 2130Z.

Discussion...An MCS was born out of the approach of a sharp mid
level shortwave that entered West Virginia this morning.
Instability was initially supported by moisture returning north of
a surface boundary. Despite moving down gradient toward lesser
instability on the east side of the Appalachian spine, the MCS at
19Z found itself at peak heating and showed no signs of immediate
weakening. In the warm advection regime near the Blue Ridge cells
were lifting in the mean low level flow and merging into the line
of moderate to heavy thunderstorms that were advancing from the
west. This merger process had boosted radar-based rain amounts to
more than an inch per hour in spots, all well beneath the melting
layer from KLWX where estimates should be most trustworthy.

With the very wet July and FFG as low as a half inch per hour
gridded or just over three quarters inch per hour county-based,
this MCS may continue to produce rainfall exceeding FFG until it
dissipates. Model guidance indicates the system weakening very
rapidly after 19Z, but given the organized radar presentation and
time of day, it may hold on until at least 21Z when it will reach
the edge of the analyzed positive mixed layer CAPE values per the
SPC mesoanalysis. All the while the system will move east,
affecting the areas that were most saturated be recent rain events.

Burke

ATTN...WFO...CTP...LWX...PHI...

ATTN...RFC...MARFC...

LAT...LON   40847695 40807595 39527684 38787770 38737810
            39337821 40127790