MESOSCALE PRECIPITATION DISCUSSION 0200
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1120 AM EDT SAT MAY 26 2018

AREAS AFFECTED...WESTERN NC...NORTHEAST TN...EASTERN WV...WESTERN
VA

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 261517Z - 262017Z

SUMMARY...SLOW MOVING SHOWERS AND EMBEDDED THUNDERSTORMS OVER THE
SOUTHERN APPALACHIANS THIS MORNING ARE FORECAST TO EXPAND IN
COVERAGE GOING INTO THE MIDDAY AND EARLY AFTERNOON HOURS.  AREAS
OF HEAVY RAIN OVER RELATIVELY SATURATED GROUND MAY LEAD TO
INSTANCES OF FLASH FLOODING.

DISCUSSION...AN ONGOING COMPLEX OF SLOW MOVING HEAVY SHOWERS AND
THUNDERSTORMS BETWEEN ROANOKE AND KNOXVILLE HAS ALREADY RESULTED
IN 1 TO 3 INCH RAINFALL AMOUNTS THROUGH 11 AM.  REGIONAL RADARS
ARE INDICATING AN INCREASE IN THIS ACTIVITY WITH A SLOW OVERALL
MOVEMENT TO THE NORTHEAST.  THE 12Z RNK SOUNDING A DEEP NEARLY
SATURATED LOWER TO MIDDLE TROPOSPHERE WITH UNIDIRECTIONAL
SOUTHWEST FLOW FROM 850-300MB.  ALTHOUGH CAPE IS NOT PARTICULARLY
IMPRESSIVE LATE THIS MORNING, MLCAPE ON THE ORDER OF 1000-1500
J/KG SHOULD BE REALIZED GOING INTO THE AFTERNOON, WITH THE HIGHEST
VALUES ALONG AND EAST OF THE BLUE RIDGE.  PW VALUES ARE FORECAST
TO INCREASE INTO THE 1.5 TO 2 INCH RANGE LATER TODAY AS COPIOUS
TROPICAL MOISTURE IS ADVECTED NORTHWARD INTO THE REGION.

MOST OF THE AVAILABLE HIGH RESOLUTION GUIDANCE (INCLUDING THE MOST
RECENT HRRR AND EXPERIMENTAL HRRR) INDICATES THE POTENTIAL FOR
LOCAL 1 TO 3 INCH RAINFALL AMOUNTS, WITH THE HIGHEST AMOUNTS
DEPICTED OVER THE SOUTHERN HALF OF THE MPD AREA.  GIVEN THE LOWER
FFG VALUES OWING TO HEAVY RAINFALL OVER THE PAST WEEK, RUN-OFF
FROM HEAVY DOWNPOURS COULD CAUSE LOCALIZED FLASH FLOODING IN SOME
VALLEY LOCATIONS.

HAMRICK

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

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

LAT...LON   39457876 39247808 38687808 37937859 37527896
            36837968 36248033 35968089 35788145 35748217
            35838277 36098309 36438317 36768290 37268226
            37928130 38398061 38928000 39257929