MESOSCALE PRECIPITATION DISCUSSION 0260
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
655 PM EDT SAT JUN 02 2018

AREAS AFFECTED...MD INTO CENTRAL AND EASTERN VA

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 022300Z - 030400Z

SUMMARY...TRAINING AND BACKBUILDING IN A HIGH MOISTURE ENVIRONMENT
COULD PRODUCE ADDITIONAL FLASH FLOODING INTO THE LATE EVENING
HOURS.

DISCUSSION...REGIONAL RADARS SHOWED AREAS OF CONVECTION EXTENDING
FROM THE MD/PA BORDER SOUTH AND SOUTHEAST INTO SOUTHEAST VA. THE
CONVECTION WAS SWIRLING AROUND A WEAK MID LEVEL CIRCULATION
LOCATED OVER SOUTHERN MD AND EASTERN VA. THE BEST INSTABILITY WAS
LOCATED OVER EASTERN MD INTO EASTERN VA...WHERE THE AIRMASS HAS
NOT YET BEEN OVERTURNED BY EARLIER CONVECTION TO A LARGE DEGREE.
FURTHER NORTH TOWARD THE PA/MD...THE INSTABILITY WAS NOT QUITE AS
ROBUST...DUE TO EARLIER STORMS.

THE ENTIRE AREA REMAINS IN A LARGE POOL OF 2.00+ INCH PRECIPITABLE
WATER AIR...WITH IN THE LOWER TO MID 70S SOUTH OF A FRONT LOCATED
OVER NJ/PA. DUE TO THE PRESENCE OF THE MID LEVEL
CIRCULATION...850-300 MB MEAN WINDS ARE GENERALLY UNDER 10 KNOTS
ACROSS MUCH OF THE AREA. THE MOST RECENT RAP SHOWED THAT
PROPAGATION VECTORS WERE OPPOSED TO THE WEAK MID LEVEL
FLOW...WHICH IS EXPECTED TO FOSTER AREAS OF TRAINING AND
BACKBUILDING INTO THE EVENING HOURS.

THERE ALSO APPEARED TO BE A SURFACE CIRCULATION ON A DEVELOPING
FRONTAL BOUNDARY OVER SOUTHEAST VA. THIS CIRCULATION COULD BE THE
FOCAL POINT FOR CONVECTION WITH LITTLE NET MOTION THROUGH THE LATE
EVENING HOURS. IN FACT...THE MOST RECENT HRRR/EXPERIMENTAL HRRR
HAVE INDICATED THE POTENTIAL FOR 4.00+ INCHES OF RAINFALL OVER
PORTIONS OF SOUTHEAST VA...WITH LOCAL AMOUNTS OVER 6.00 INCHES.

SHOULD CONVECTION CONTINUE TO FIRE NEAR THE LOW LEVEL
CIRCULATION...THESE RAINFALL AMOUNTS ARE PLAUSIBLE...AT LEAST AS
HIGH END AMOUNTS. THE ADDITIONAL HEAVY RAINFALL COULD EXACERBATE
ONGOING FLOODING OR INITIATE NEW FLOODING THROUGH 03/04Z.

HAYES

ATTN...WFO...AKQ...LWX...PHI...

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

LAT...LON   39647759 39647603 38677571 37347574 36327632
            36497754 37037815 39177794