MESOSCALE PRECIPITATION DISCUSSION 0253
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
747 PM EDT SAT JUN 20 2015
 
AREAS AFFECTED...SOUTHEAST PA...EASTERN MD...DC...EASTERN VA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 202344Z - 210400Z
 
SUMMARY...STORMS CAPABLE OF PRODUCING HEAVY RAINFALL WILL BE
PROPAGATING FROM WEST TO EAST ACROSS PORTIONS OF THE MID ATLANTIC
REGION THROUGH 04Z. 

DISCUSSION...THUNDERSTORMS WERE FORMING IN A REGION OF DIFLUENCE
EAST OF WHAT HAD BEEN TROPICAL DEPRESSION BILL AND WILL BE MOVING
INTO AN ENVIRONMENT CHARACTERIZED BY MLCAPES ON THE ORDER OF 2000
J PER KG AND 3000 J PER KG AND PRECIPITABLE WATER VALUES OF 1.75
TO 2.00 INCHES.  DEW POINTS WERE IN THE 70S...WITH SOME MID- TO
UPPER 70S REPORTED BY SEVERAL AWOS SITES IN THE AREA.  THUS EXPECT
THE CELLS TO BE EFFICIENT RAINFALL PRODUCERS CAPABLE OF PRODUCING
1 TO 2 INCH PER HOUR RATES.  SEVERAL INCHES OF RAIN IN A SHORT
AMOUNT OF TIME IS CERTAINLY POSSIBLE AND THOSE RAINFALL AMOUNTS
WERE ADVERTISED IN THE 3 HOURLY RAINFALL GRAPHICS FROM THE ARW AND
NMMB HI RES GUIDANCE AS WELL AS THE HRRR.

GIVEN FFG VALUES ON THE ORDER OF 2.5 TO 3 INCHES PER 3 HOURS..SOME
FLOODING IS POSSIBLE.  SOME PROBLEMS RELATED TO RUNOFF MAY ALSO BE
POSSIBLE IN URBAN AREAS DESPITE RAINFALL AMOUNTS BEING BELOW FFG
VALUES.

BANN

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

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

LAT...LON   40477560 39987513 39237563 38257610 37617670 
            37057765 37177822 37807865 38197807 38747770 
            39797746 40407644