MESOSCALE PRECIPITATION DISCUSSION 0208
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 PM EDT THU MAY 11 2017

AREAS AFFECTED...SOUTHERN WV & SOUTHWEST VA

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

VALID 111759Z - 112359Z

SUMMARY...SHOWERS AND THUNDERSTORMS COULD TRAIN AT TIMES ACROSS
THE REGION DURING THE NEXT SEVERAL HOURS.  CONSIDERING SATURATED
SOILS AND LOW FLASH FLOOD GUIDANCE VALUES, FLOODING IS POSSIBLE.

DISCUSSION...PARTLY SUNNY SKIES TO THE SOUTH OF A SLOWLY MOVING
COLD FRONT HAVE LED TO A SLOW UPTICK IN INSTABILITY.  MLCAPES ARE
500+ J/KG ACROSS SOUTHWEST WV AND SHOULD RISE FURTHER WITH TIME. 
A NARROW BAND OF SHOWERS AND THUNDERSTORMS HAS RECENTLY DEVELOPED
IN EASTERN KY.  AS THE FLOW PATTERN IS UNIDIRECTIONAL WITH HEIGHT,
CELL TRAINING IS A CONCERN.  INFLOW AT 850 HPA IS 20-30 KTS IS
SLIGHTLY CONVERGENT ACROSS THE AREA.  PRECIPITABLE WATER VALUES
WERE CLOSE TO 1.5" AT 13Z PER GPS VALUES.  BULK SHEAR IN THE 0-6
KM LAYER IS AROUND 40 KTS.

THE EXPECTATION IS FOR MLCAPES TO RISE ANOTHER 500+ J/KG WHICH
SHOULD HELP LEAD TO SOME INCREASE IN CELL COVERAGE ACROSS
SOUTHWEST WV AND SOUTHWEST VA.  GFS-BASED GALVEZ-DAVISON
INSTABILITY VALUES PEAK AROUND 00Z ACROSS SOUTHWEST WV WITH VALUES
NEAR 30.  HOURLY RAIN RATES OF 1-1.5" SHOULD BE POSSIBLE LOCALLY
WHERE CELLS TRAIN, WHICH WOULD BE PROBLEMATIC IN THIS AREA.  THE
LOW FLASH FLOOD GUIDANCE VALUES WERE CAUSED BY A WET 30 DAY
PERIOD, AS 100-200% OF AVERAGE RAINFALL HAS OCCURRED SINCE APRIL
11.  MESOSCALE GUIDANCE ADVERTISES LOCAL AMOUNTS NEAR 2".  RECENT
HRRR RUNS APPEAR REASONABLE IN THIS AREA.  AS SOILS ARE LIKELY
PARTIALLY SATURATED, FLOOD ISSUES ARE POSSIBLE.

ROTH

ATTN...WFO...ILN...JKL...LMK...LWX...MRX...RLX...RNK...

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

LAT...LON   38718128 38658045 38548006 37887911 37317894
            37217911 37517966 37198033 36768131 37168180
            37078259 37088288 37588366 38368468 38408335
            38518261