MESOSCALE PRECIPITATION DISCUSSION 0370
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
221 AM EDT THU JUN 28 2018

AREAS AFFECTED...EASTERN PA...SOUTHEAST NY...NORTHERN NJ...WESTERN
MA...WESTERN CT

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 280620Z - 281120Z

SUMMARY...CONVECTION TRAINING OVER AREAS THAT RECEIVED HEAVY
RAINFALL WEDNESDAY EVENING COULD POSE A FLASH FLOOD THREAT THROUGH
THE EARLY MORNING HOURS.

DISCUSSION...REGIONAL DOPPLER RADARS ARE INDICATING AN INCREASE IN
THUNDERSTORM COVERAGE ACROSS MUCH OF EASTERN PENNSYLVANIA EARLY
THIS MORNING.  THE LATEST GOES 16 INFRARED SATELLITE IMAGERY IS
ALSO INDICATING COOLING CONVECTIVE CLOUD TOPS WITH STRONG
UPDRAFTS.  THIS ACTIVITY IS EXPECTED TO PROGRESS TOWARDS THE
NORTHEAST AND AFFECT NORTHERN NEW JERSEY AND INTO INTERIOR
SOUTHEAST NEW YORK, AND THEN WESTERN NEW ENGLAND.  RAINFALL RATES
OF 2 INCHES PER HOUR HAVE BEEN OBSERVED NEAR HARRISBURG AND THERE
IS THE POTENTIAL FOR ADDITIONAL HEAVY RAINFALL THROUGH THE
REMAINDER OF THE OVERNIGHT HOURS.

THESE STORMS WILL HAVE AN AMPLE SUPPLY OF DEEP MOISTURE AS 2 INCH
PWS ARE ADVECTED INTO THE REGION VIA A 30+ KNOT LOW LEVEL INFLOW,
ALONG WITH DEEP NEARLY UNIDIRECTIONAL FLOW ALOFT.  THERE IS ALSO
ABOUT 500 TO 1000 J/KG OF MUCAPE PER THE LATEST SPC ANALYSIS. 
THESE FACTORS COMBINED WITH AN APPROACHING SHORTWAVE ALOFT WILL
HELP SUSTAIN THE CONVECTION THROUGH 11Z THIS MORNING.

THE LATEST SUITE OF HIGH RES GUIDANCE IS INDICATING THE POTENTIAL
FOR SWATHS OF 1 TO 3 INCH RAINFALL AMOUNTS WITH THESE STORMS OVER
THE NEXT SEVERAL HOURS.  THE AXIS OF GREATEST RAINFALL WILL LIKELY
BE FROM HARRISBURG TO WESTERN MASSACHUSETTS.  FLASH FLOODING IS
POSSIBLE GIVEN THE REPEATED ROUNDS OF HEAVY RAINFALL.

D. HAMRICK

ATTN...WFO...ALY...BGM...BOX...CTP...OKX...PHI...

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

LAT...LON   43007341 42747293 42107279 41377328 40847407
            40297483 39807574 39767718 39937753 40327768
            41127715 41757623 42417527 42927434