MESOSCALE PRECIPITATION DISCUSSION 0471
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1134 AM EDT TUE JUL 17 2018

AREAS AFFECTED...SOUTHEAST NEW YORK AND SOUTHERN NEW ENGLAND

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

VALID 171534Z - 172134Z

SUMMARY...SLOW MOVING HEAVY SHOWERS AND THUNDERSTORMS ARE EXPECTED
FROM SOUTHEAST NEW YORK TO EXTREME SOUTHWEST MAINE THROUGH MOST OF
THE AFTERNOON.  HEAVY RAINFALL RATES IN EXCESS OF 1.5 INCHES PER
HOUR AT TIMES COULD LEAD TO INSTANCES OF FLASH FLOODING.

DISCUSSION...LATEST GOES 16 SATELLITE IMAGERY AND REGIONAL DOPPLER
RADARS ARE INDICATING SLOW MOVING BANDS OF THUNDERSTORMS EXTENDING
FROM SOUTHWEST TO NORTHEAST.  CONDITIONS WILL BECOME INCREASINGLY
FAVORABLE OVER THE NEXT FEW HOURS AS THE LEADING EDGE OF MID LEVEL
HEIGHT FALLS APPROACHES THE REGION.  MLCAPE IS PROGGED BY THE SPC
MESOANALYSIS TO REACH THE 1500 TO 2500 J/KG RANGE IN THE PRESENCE
OF 1.8 TO 2.2 INCH PWS.  MORNING RAOBS IN THIS AREA ALSO WERE
INDICATING DEEP LAYER UNI-DIRECTIONAL FLOW FROM THE SOUTHWEST,
WITH THE POTENTIAL FOR SOME BACK-BUILDING OF CONVECTIVE ELEMENTS.

THE HIGH RES MODEL SUITE IS PORTRAYING THE POTENTIAL FOR
WIDESPREAD ONE INCH AMOUNTS THROUGH 5 PM, WITH SCATTERED CLUSTERS
OF 2 TO 4 INCH TOTALS.  THE WRF NSSL IS MORE ROBUST WITH THE
AMOUNTS, WITH GREATER COVERAGE OF AT LEAST 2 INCHES.  A MITIGATING
FACTOR HERE ARE THE RELATIVELY HIGH FLASH FLOOD GUIDANCE VALUES
OVER PARTS OF THIS REGION.  HOWEVER, THE POTENTIAL FOR HIGH
RAINFALL RATES WILL BE ENOUGH TO OVERCOME THE INITIALLY DRYER
GROUND CONDITIONS.

D. HAMRICK

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

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

LAT...LON   43867021 43596995 43107002 42677033 42207066
            41797128 41397176 40967189 40597300 40487362
            40427402 40497438 40777442 41137446 41847458
            42417434 42917367 43217245 43497159 43857084