MESOSCALE PRECIPITATION DISCUSSION 0175
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
707 PM EDT THU JUL 03 2014
 
AREAS AFFECTED...SRN NY...WRN MA...CT...RI...NRN NJ...ERN PA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 032306Z - 040236Z
 
SUMMARY...AN ENHANCED HEAVY RAIN THREAT EXISTS IN THE SHORT
TERM...THROUGH 03Z...NEAR THE URBAN AREAS SURROUNDING NYC AND
PROGRESSING TOWARD MA/CT.

DISCUSSION...AFTERNOON CONVECTION WAS INITIATED OFF TERRAIN
FEATURES PERPENDICULAR TO THE MEAN LAYER FLOW AND IN A REGION OF
MORE DEEPLY MIXED BOUNDARY LAYER AIR. AFTER SHOWING STEADY
EASTWARD PROGRESSION EARLY...THE LIKELIHOOD OF SLOWER MOVEMENT AND
ORGANIZED TRAINING HAD INCREASED AS THIS CONVECTION REACHED THE
COASTAL PLAIN...WHERE DOWNDRAFT CAPE WAS RELATIVELY LESS...AND
ECHOES HAD BECOME ORIENTED MORE PARALLEL TO THE DEEP LAYER FLOW. 

A LINE ESTABLISHED OVER THE PA/NJ/NY BORDER REGION WAS LIKELY TO
BE SUSTAINED BY SBCAPE OVER 2500 J/KG AND MODEST SOUTHWESTERLY
INFLOW JUST ABOVE THE SURFACE. EXPECT A SLOW PUSH TO THE EAST AND
SOUTHEAST. WITH TRAINING OCCURRING ALONG THE LEADING EDGE...AND
ABSORPTION OF NORTHWARD DRIFTING CELLS IN THE INFLOW...THE
ENVIRONMENT WILL TREND TOWARD MORE EFFICIENT RAIN PRODUCTION.

DUAL POL ESTIMATES FROM INSIDE THE RANGE OF THE MELTING LAYER
SUGGESTED ACCUMULATION RATES WERE RISING TOWARD 2 INCHES/HR.
CONSECUTIVE RUNS OF THE HRRR HAVE PRODUCED 2 TO 3 INCH SWATHS IN
THIS REGION...AND ISOLATED 4 INCH TOTALS ARE POSSIBLE GIVEN THE
EXPECTED TRAINING. THIS WILL LIKELY PRODUCE FLASH FLOODING IN
URBAN AREAS WHERE FLASH FLOOD GUIDANCE IS LOWEST...AND MAY DO SO
IN FAST RESPONDING STREAMS IN OTHER AREAS WHERE FLASH FLOOD
GUIDANCE IS ABOUT 3 INCHES IN 3 HOURS.

BURKE

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

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

LAT...LON   39797572 39847395 40247197 40897136 41557122 41987128
            42297146 42607168 42637222 42627310 42107396 41567505
            41027593 40427622 39797572 
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