MESOSCALE PRECIPITATION DISCUSSION 0356
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
228 PM EDT THU JUN 16 2016
 
AREAS AFFECTED...ERN OH/WRN PA INTO THE PANHANDLES OF WV/MD AND
NRN VA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 161827Z - 170000Z
 
SUMMARY...REPEATING ROUNDS OF CONVECTION ACROSS PORTIONS OF ERN
OHIO AND WRN PENNSYLVANIA INTO NRN VIRGINIA MAY POSE A FLASH FLOOD
THREAT THROUGH THE AFTERNOON/EARLY EVENING HOURS...ESPECIALLY
ACROSS AREAS OF LOWER FLASH FLOOD GUIDANCE. 

DISCUSSION...AT 18Z...SATELLITE AND RADAR TRENDS SHOWED RAPIDLY
DEVELOPING CONVECTION AHEAD OF A COLD FRONT MOVING THROUGH CNTRL
OHIO. SUFFICIENT HEATING BEHIND A ROUND OF RAINFALL WHICH MOVED
THROUGH WRN PENNSYLVANIA BETWEEN 13-16Z SEEMS TO HAVE ALLOWED FOR
REBUILDING OF INSTABILITY WITH ROUGHLY 500 TO 1500 J/KG IN PLACE
FROM THE OHIO/PENNSYLVANIA BORDER INTO NRN VIRGINIA...SOUTH OF A
STATIONARY FRONT AND OUTFLOW BOUNDARY. WHILE GPS SITES AND BLENDED
TPW IMAGERY SHOWED PRECIPITABLE WATER VALUES PEAKING NEAR 1.50
INCHES AS OF 18Z...THESE VALUES ARE EXPECTED TO INCREASE PAST 1.75
INCHES INTO NRN VIRGINIA THROUGH 00Z AHEAD OF AN APPROACHING
CLOSED LOW IN SRN MICHIGAN. 

EARLIER CONVECTION ACROSS WRN PENNSYLVANIA PRODUCED 0.50 TO 1.00
INCHES OF RAIN IN AN AREA WHERE FLASH FLOOD GUIDANCE IS AS LOW AS
1 IN/HR IN SWRN PORTIONS OF THE STATE. ADDITIONAL CONVECTION
CURRENTLY MOVING INTO THE REGION IS EXPECTED TO EXPAND THROUGH THE
AFTERNOON AS THE UPPER LOW APPROACHES. SLOWER STORM MOTIONS ACROSS
NWRN PENNSYLVANIA MAY ALLOW FOR SOME 1-2 IN/HR RAIN RATES TO HANG
UP AND POSE A FLASH FLOOD RISK DESPITE THE HIGHER FFG IN THIS
PORTION OF THE STATE.

AS THE UPPER LOW APPROACHES...INCREASING UPPER DIFFLUENCE SHOULD
HELP CONVECTION TO BUILD WITH A PROGRESSIVE LINE LIKELY MOVING
THROUGH THE SRN PORTION OF THE MPD THREAT AREA BY LATE AFTERNOON.
HOWEVER...ANY STORMS THAT DEVELOP OUT AHEAD OF THE MAIN LINE ALONG
WITH CELL MERGERS MAY POSE A FLASH FLOOD RISK INTO NRN VIRGINIA BY
EARLY EVENING. 

RECENT RUNS OF THE HRRR AND PARALLEL HRRR SUPPORT THIS IDEA...BUT
COULD BE A LITTLE SLOW WITH PROPAGATION TOWARD THE SOUTHEAST WHICH
IS WHY THE THREAT AREA WAS EXPANDED FARTHER SOUTH AND EAST THAN
THE HRRRS MIGHT SUGGEST.

OTTO

ATTN...WFO...CLE...CTP...LWX...PBZ...RLX...

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

LAT...LON   42098022 41947953 40987851 40627803 40017741 
            39437698 38997684 38717700 38537772 39217971 
            39708118 39968178 40598163 41008138 41708100 
            41958070