MESOSCALE PRECIPITATION DISCUSSION 0471
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
231 PM EDT WED JUL 12 2017

AREAS AFFECTED...SOUTHEAST NY & SOUTHERN NEW ENGLAND

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

VALID 121830Z - 130000Z

SUMMARY...THUNDERSTORMS ARE BEGINNING TO EXPAND IN COVERAGE ACROSS
THE REGION.  HOURLY RAIN RATES TO 2.5" WITH LOCAL AMOUNTS TO 4"
ARE ANTICIPATED.

DISCUSSION...IN THE 18Z MESOSCALE ANALYSIS, A STATIONARY FRONT
SHOWS UP IN SOUTHERN NEW ENGLAND AND EASTERN NY AHEAD OF A SURFACE
LOW.  INFLOW AT 850 HPA IS SLIGHTLY CONVERGENT AND ~15 KTS, BUT
EFFECTIVE BULK SHEAR OF ~30 KTS IS STARTING TO LEAD TO SOME
ORGANIZATION IN THE FORM OF OCCASIONAL SHORT TRAINING BANDS. 
PRECIPITABLE WATER VALUES ARE CLOSE TO 2".  THERE IS SOME
INDICATION OF BACKBUILDING CONVECTION ACROSS CT AND MA TOWARDS THE
BERKSHIRES.  MLCAPE VALUES ARE 1000-2000 J/KG.

THERE IS A SIGNAL FOR POCKETS OF HEAVY RAINFALL ACROSS THIS REGION
UNTIL 00Z WHEN INSTABILITY IS EXPECTED TO BECOME EXHAUSTED. 
ORGANIZED THUNDERSTORMS SHOULD MOVE EAST-SOUTHEAST AT ~ 25 KTS. 
THE BOUNDARY ACROSS SOUTHERN NEW ENGLAND IS EXPECTED TO SAG SOUTH
AS OUTFLOW BOUNDARIES PUSH IT SOUTHWARD.  SLOWLY INCREASING INFLOW
AT 850 HPA COULD LEAD TO SOME CONTINUED BACKBUILDING, BUT THE MAIN
HEAVY RAIN THREAT IS EXPECTED TO OCCUR IN SHORT TRAINING BANDS. 
HOURLY RAIN RATES UP TO 2.5" WITH LOCAL AMOUNTS TO 4" ARE EXPECTED.

ROTH

ATTN...WFO...ALY...BGM...BOX...GYX...OKX...

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

LAT...LON   43027096 42647038 42357080 42097048 42177009
            41886978 41357029 41277183 41027375 41707483
            42827602