MESOSCALE PRECIPITATION DISCUSSION 0357
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
807 PM EDT THU JUN 16 2016
 
AREAS AFFECTED...NORTHERN AND EASTERN VA...WESTERN/CENTRAL
MD...FAR SOUTHERN PA...FAR EASTERN WV 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 170006Z - 170600Z
 
SUMMARY...REPEATING ROUNDS OF CONVECTION MAINLY ACROSS PORTIONS OF
MD AND VA MAY POSE A FLASH FLOOD THREAT THROUGH THE EVENING AND
INTO THE EARLY MORNING HOURS...ESPECIALLY ACROSS AREAS OF LOWER
FLASH FLOOD GUIDANCE. 

DISCUSSION...AT 23Z...SATELLITE AND RADAR TRENDS SHOWED CONVECTION
HAD BECOME WELL ORGANIZED ALONG AND AHEAD OF A COLD FRONT FROM
SOUTHERN PA INTO WESTERN VA AND EASTERN WV.  SURFACE BASED CAPES
HAD BUILT INTO THE 1500 TO 2000 J PER KG RANGE OVER PORTIONS OF
VA/MD WHERE THE SUN WAS ABLE TO BREAK THROUGH THE CLOUD
COVER...AND THEN TAPER OFF TO THE 500 TO 1000 J PER KG RANGE OVER
PORTIONS OF PA...WITH PRECIPITABLE WATER VALUES IN EXCESS OF 1.75
INCHES.  THIS AREA OF MOISTURE AND INSTABILITY WAS LOCATED AHEAD
OF AN AREA OF LOW PRESSURE WHICH WAS MAKING ITS WAY SOUTHEAST FROM
ERN OH.

THE ON-GOING CONVECTION WAS MOVING INTO A REGION WHERE 1- AND
3-HOUR FLASH FLOOD GUIDANCE WAS ON THE ORDER OF 3 INCHES OR MORE. 
RAINFALL RATES OF 1 TO 2 INCHES PER HOUR HAVE BEEN OBSERVED..WHICH
SETS UP THE POSSIBILITY OF FLASH FLOODING IN REGIONS WHICH RECEIVE
MULTIPLE ROUNDS OF HEAVY RAINFALL.

RECENT RUNS OF THE HRRR AND THE PARALLEL RUNS OF THE HRRR HAVE
BEEN SHOWING 6-HOUR QPF AMOUNTS OF 1.5 TO 3 INCHES MAINLY CONFINED
TO CENTRAL AND EASTERN VA...BUT EXTENDING INTO ADJACENT PORTIONS
OF MD/PA/WV UNTIL THE BEST FORCING CLEARS THOSE AREAS.

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.

BANN

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

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

LAT...LON   39937792 39887724 39467683 38987675 38507649 
            38057635 37527630 36757656 36627731 37237846 
            37328035 38028107 38198059 38257962 38687863 
            39327821