MESOSCALE PRECIPITATION DISCUSSION 0149
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
357 PM EDT TUE MAY 15 2018

AREAS AFFECTED...PORTIONS OF THE SRN/CNTRL APPALACHIANS

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

VALID 151956Z - 160145Z

SUMMARY...SCATTERED THUNDERSTORMS OVER THE SOUTHERN AND CENTRAL
APPALACHIANS WILL BE CAPABLE OF 1-2+ IN/HR OVER AREAS THAT HAVE
LOW FLASH FLOOD GUIDANCE. WHILE STORMS ARE NOT EXPECTED TO BE
HIGHLY ORGANIZED...COVERAGE OF HIGH RAIN RATES SHOULD BE SCATTERED
ACROSS THE REGION.

DISCUSSION...A COMBINATION OF VISIBLE AND RADAR REFLECTIVITY
THROUGH 1930Z SHOWED SCATTERED CONVECTION FORMING OVER THE HIGHER
TERRAIN OF THE CENTRAL AND SOUTHERN APPALACHIANS. GENERALLY CLEAR
SKIES DURING THE LATE MORNING/EARLY AFTERNOON HOURS HAVE ALLOWED
MLCAPE VALUES TO RISE INTO THE 1000-2000 J/KG RANGE...SOUTH OF A
COLD FRONT EXTENDING FROM WESTERN PENNSYLVANIA INTO THE LOWER OHIO
VALLEY AT 19Z. THE REGION IS LOCATED IN AN AREA OF WEAK LOW-MID
LEVEL FLOW...ACCOUNTING FOR SLOW STORM MOTIONS...GENERALLY 10 KT
OR LESS...AMID AN ENVIRONMENT OF 1.25 INCH PRECIPITABLE WATER
VALUES PER RECENT GPS VALUES.

WHILE OBSERVATIONS HAVE NOT BEEN CO-LOCATED WITH MAXIMUM RADAR
ESTIMATED RAINFALL RATES OF 2+ IN/HR...A WUNDERGROUND.COM
OBSERVATION IN WESTERN VIRGINIA...SOUTH IF I-81...SHOWED ROUGHLY 1
INCH FELL IN ABOUT 60 MINUTES ENDING AT 19Z. RECENT HRRR AND
EXPERIMENTAL HRRR RUNS HAVE SHOWN A CONSISTENT SIGNAL FOR 1-3
INCHES OF RAIN...SCATTERED FROM NORTHEASTERN TENNESSEE INTO
SOUTHERN WEST VIRGINIA AND WESTERN VIRGINIA THROUGH 01Z. GIVEN A
LACK OF LARGER SCALE FORCING...CONVECTION IS EXPECTED TO DIMINISH
WITH THE LOSS OF DAYTIME HEATING...BEYOND 01Z...BUT UNTIL THEN...A
FEW LOCATIONS MAY SEE SHORT TERM HEAVY RAINFALL ON TOP OF LOW
FLASH FLOOD GUIDANCE VALUES OF 1.5 TO 2.5 INCHES IN 1 HOUR.

OTTO

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

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

LAT...LON   38327939 38217889 37957879 37457914 36817971
            36208103 35848252 35628349 35758432 35848500
            36178513 36708458 37318309 37898164 38318028