MESOSCALE PRECIPITATION DISCUSSION 0276
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
136 PM EDT SAT JUN 09 2018

AREAS AFFECTED...FAR NORTHERN VA...D.C...CENTRAL/EASTERN
MD...DE...SOUTHERN NJ

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

VALID 091735Z - 092335Z

SUMMARY...LOCALLY VERY HEAVY RAINFALL IS EXPECTED THIS AFTERNOON
WITH CLUSTERS OF BACKBUILDING SHOWERS AND THUNDERSTORMS. GIVEN THE
VERY INTENSE RAINFALL RATES...FLASH FLOODING IS LIKELY AND MAY
IMPACT THE D.C./BALTIMORE METRO AREAS.

DISCUSSION...GOES-16 VISIBLE SATELLITE IMAGERY SHOWS CONVECTIVE
INITIATION WELL UNDERWAY ACROSS PORTIONS OF CENTRAL/EASTERN
MD...DE AND SOUTHERN NJ AS DIURNALLY ENHANCED INSTABILITY POOLS
ALONG A QUASI-STATIONARY FRONT DRAPED ACROSS THE CENTRAL
MID-ATLANTIC REGION. MLCAPE VALUES HAVE RISEN TO AS MUCH AS 1500
J/KG AND PWATS ACROSS THE REGION HAVE RISEN TO NEAR 1.75 INCHES.

THE SYNOPTIC FRONT COUPLED WITH SMALL SCALE BAY/RIVER BREEZE
CONVERGENCE NEAR D.C. AND UP ALONG AND EAST OF I-95 TO THE INNER
HARBOR AREA OF BALTIMORE WILL ALLOW FOR A LOCALLY FOCUSED CONCERN
SLOW-MOVING AND BACKBUILDING SHOWERS AND THUNDERSTORMS.
MEANWHILE...FARTHER EAST OVER THE DELMARVA...THE SAME FRONT
COUPLED WITH LOCALLY ENHANCED CONVERGENCE AHEAD OF AN AREA OF LOW
PRESSURE IS EXPECTED TO CONCENTRATE HEAVY SHOWERS AND
THUNDERSTORMS. THE ENVIRONMENT IS HIGHLY CONDUCIVE FOR
BACKBUILDING/REPEATING CONVECTIVE CELL ACTIVITY...AND THIS WILL BE
AIDED BY ADDITIONAL DIURNAL HEATING AND PROXIMITY OF AT LEAST SOME
MODEST UPPER LEVEL DIVERGENCE OVER THE REGION.

A CONSENSUS OF THE 12Z ARW/NMMB SOLUTIONS AND RECENT HRRR/HRRRX
GUIDANCE FAVORS AS MUCH AS 2 TO 4 INCHES OF RAIN...WITH THE
HEAVIEST TOTALS OVER THE DELMARVA AND FAR SOUTHERN NJ WHERE
LOCALLY OVER 5 INCHES WILL BE POSSIBLE. GIVEN THE LOCALLY
URBANIZED ENVIRONMENT....RAINFALL RATES OF OVER 2 INCHES/HR...AND
BACKBUILDING NATURE OF THE ACTIVITY...THE THREAT OF FLASH FLOODING
IS ELEVATED.

ORRISON

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

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

LAT...LON   39707542 39667468 39547444 39207449 38947484
            38617496 38347501 37847544 37767605 37867664
            38137723 38417749 38957776 39357759 39627719
            39547617