MESOSCALE PRECIPITATION DISCUSSION 0163
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
121 PM EDT MON JUN 01 2015
 
AREAS AFFECTED...WV/VA BORDER INTO NRN VA...NRN MD AND EXTENDING
INTO CNTRL NJ 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 011720Z - 012320Z
 
SUMMARY...CONVECTIVE COVERAGE WILL INCREASE INTO THE REMAINDER OF
THE AFTERNOON AND IS EXPECTED TO PROMOTE A FLASH FLOOD THREAT WITH
TRAINING CELLS FROM THE WV/VA BORDER TO PORTIONS OF THE NRN
MID-ATLANTIC COAST. LOCALLY VERY HEAVY RAIN IS EXPECTED WITH
TOTALS OF 4-8 INCHES POSSIBLE THROUGH 00Z WITH FLASH FLOODING
LIKELY IN A FEW LOCATIONS.

DISCUSSION...AT 17Z...SURFACE OBSERVATIONS SHOWED A NEARLY
STATIONARY FRONT EXTENDING WEST ACROSS SRN NEW JERSEY...ARCING
WNWWD INTO A WEAK SURFACE LOW LOCATED IN S-CNTRL PA...AND THEN
DRAPING SWWD INTO ERN KY. MOSTLY CLEAR SKIES WITHIN THE WARM
SECTOR OF THE FRONT HAVE ALLOWED SURFACE BASED CAPE VALUES TO RISE
INTO THE 1000-2000 J/KG RANGE BASED ON ADJUSTMENTS TO THE 12Z KIAD
SOUNDING FOR CURRENT AREA  TEMPERATURES/DEWPOINTS AND RECENT GPS
PRECIPITABLE WATER VALUES ACROSS NRN MARYLAND WERE 1.5 TO 1.7
INCHES WHICH IS NEAR +2 SD FOR EARLY JUNE. THIS ENVIRONMENT IS
SUPPORTIVE OF HEAVY RAINFALL RATES OF 1-2 INCHES PER HOUR AND
CONVECTIVE CELLS HAVE ALREADY DEVELOPED ALONG THE HIGHER
ELEVATIONS OF WV...VA...WRN MD AND S-CNTRL PA. 

MEAN STORM MOTIONS ARE EXPECTED TO RANGE BETWEEN 10 AND 20 KTS
TOWARD THE ENE AND NE TOWARD EVENING WITH UNIDIRECTIONAL FLOW
THROUGHOUT THE CLOUD BEARING LAYER. WHILE LOW LEVEL WINDS ARE
EXPECTED TO REMAIN SOMEWHAT WEAK WITH PRESENT VALUES OF 10-20
KTS...THE PATTERN IS FAVORABLE FOR REPEAT STORM MOTIONS JUST NEAR
THE FRONT EARLY THIS AFTERNOON...WITH MOVEMENT/SHIFTING OF
TRAINING CELLS POSSIBLE INTO THE MAJOR URBAN CORRIDORS OF
PHILADELPHIA...BALTIMORE AND WASHINGTON FOR THE EVENING RUSH HOUR.
FLASH FLOODING IS OF SPECIAL CONCERN ACROSS PORTIONS OF NRN MD AND
SERN PA WHICH RECEIVED LOCALLY HEAVY RAINFALL LATE LAST NIGHT.

00Z AND 12Z HI-RES MODELS WERE IN GOOD AGREEMENT ON THIS SETUP AND
RECENT OBSERVATIONAL TRENDS SEEM TO SUPPORT MODEL DEVELOPMENT SO
FAR. IN FACT...THE 12Z NMM/ARW/NSSL WRF AGREE WITH RAINFALL TOTALS
OF 4-8 INCHES THROUGH 00Z ACROSS PORTIONS OF THE THREAT AREA.

OTTO

ATTN...WFO...AKQ...CTP...LWX...PBZ...PHI...RLX...RNK...

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

LAT...LON   40767607 40127400 39587386 39107494 38627614 
            38437702 38097905 37388128 37448167 37778164 
            38428072 38817981 39647879 40527763