MESOSCALE PRECIPITATION DISCUSSION 0328
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
945 AM EDT FRI JUN 16 2017

AREAS AFFECTED...EASTERN WV & WESTERN VA

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

VALID 161344Z - 161944Z

SUMMARY...PULSE CONVECTION IS EXPECTED TO INCREASE COVERAGE AND
INTENSITY LATE THIS MORNING AND THIS AFTERNOON.  HOURLY RAIN RATES
UP TO 2" WITH LOCAL AMOUNTS TO 4" ARE EXPECTED.

DISCUSSION...ERODING CIN HAS LED TO NEW SURFACE-BASED CONVECTIVE
DEVELOPMENT IN SOUTHWEST WV AND NORTHWEST NC.  EXPERIMENTAL
GOES-16 IMAGERY SHOWS NEW CUMULUS DEVELOPMENT IN THE BLUE RIDGE
MOUNTAINS WITHIN AN AREA OF PARTLY SUNNY SKIES.  UPSTREAM, A
SHORTWAVE ALOFT IS SEEN ON WATER VAPOR IMAGERY THIS MORNING MOVING
INTO EASTERN OH.  MLCAPES ARE CURRENTLY 500-1000 J/KG.  LOW-LEVEL
INFLOW IS WEAK AND CYCLONIC ACROSS THE REGION, WITH EFFECTIVE BULK
SHEAR LESS THAN 25 KTS, WHICH SHOULD KEEP CONVECTION PULSE IN
NATURE.  PRECIPITABLE WATER VALUES OF 1.75-2" EXIST HERE. 

WITH SKIES PARTLY SUNNY, BELIEVE MLCAPES SHOULD BUILD ANOTHER
500-1000 J/KG DUE TO DAYTIME HEATING, REACHING ~1500 J/KG. 
TOPOGRAPHY SHOULD ACT AS THE PRIMARY CONVECTIVE FOCUS, WITH STORMS
MOVING WITH THE MEAN 850-400 HPA FLOW AND FORWARD PROPAGATING
CONVECTIVE VECTORS TO THE EAST-NORTHEAST TO NORTHEAST AT 10-15
KTS.  THE BACK EDGE OF THE THREAT AREA APPEARS TO BE MARKED BY AN
AREA OF PROGRESSIVE SHOWERS/ THUNDERSTORMS MOVING INTO FAR
SOUTHWEST WV ON THE WEST (AS SKIES IN THEIR WAKE ARE OVERCAST) AND
NEW CONVECTION IN NORTHWEST NC ON THE SOUTH WHICH SHOULD BOTH
FORWARD PROPAGATE INTO THE DEVELOPING INSTABILITY POOL AND
EVENTUALLY LEAD TO CELL MERGERS. SHORT PERIODS OF CELL TRAINING
ARE POSSIBLE AS THE FLOW IS NEARLY UNIDIRECTIONAL WITH HEIGHT.

THE PATTERN FROM THE 00Z SPC WRF AND RECENT RAP/HRRR RUNS APPEAR
TO HAVE CAPTURED THE THREAT AREA BEST.  THE AVAILABLE MOISTURE
SUPPORTS HOURLY RAIN RATES TO 2", WITH THE MESOSCALE GUIDANCE
SHOWING A SIGNAL FOR LOCAL AMOUNTS OF ~4".  SOILS IN THIS REGION
HAVE BEEN PARTIALLY SATURATED BY RECENT RAINFALL, AND IN SOME
AREAS, THE TOPOGRAPHY IS RUGGED.  THE 06Z SSEO NEIGHBORHOOD
PROBABILITIES OF EXCEEDING THE THREE HOUR FLASH FLOOD GUIDANCE
BREACHES 70% FROM 18-22Z.  FLASH FLOODING IS A CONCERN.

ROTH

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

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

LAT...LON   39687870 39507769 39057788 38467816 37887840
            36757902 36447975 36258044 36118154 36398173
            36828151 37118153 37628214 37758225 38318230
            39008126 39407969