Flash Flood Guidance
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000
AWUS01 KWNH 220828
FFGMPD
CTZ000-NYZ000-NJZ000-DEZ000-MDZ000-221227-

MESOSCALE PRECIPITATION DISCUSSION 0428
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
427 AM EDT WED OCT 22 2014

AREAS AFFECTED...DE/NJ/SOUTHEASTERN NY...

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

VALID 220827Z - 221227Z

SUMMARY...OVERNIGHT CONVECTION CONTINUES TO BLOSSOM WITH HEAVY
PRECIPITATION CORES CURRENTLY STRADDLING THE NJ/LONG ISLAND COAST.
DUAL-POL RADAR DATA SUGGESTS HEFTY HOURLY RAINFALL RATES IN EXCESS
OF 2 INCHES PER HOUR. IN SPITE OF THE MODEST FFG VALUE IN
PLACE...EXPECT AREAS OF LOCALIZED FLASH FLOODING POSSIBLE WHERE
THE CONVECTION TRAINS.

DISCUSSION...CONVECTION HAS GRADUALLY PICKED UP IN INTENSITY THE
PAST COUPLE HOURS WITH LIGHTNING BECOMING MORE PREVALENT ALONG THE
NJ COASTLINE. THIS ACTIVE PRECIPITATION HAS SPARKED ALONG A
COASTAL FRONT WHICH STRETCHES FROM THE DELMARVA PENINSULA UP
ACROSS LONG ISLAND AND INTO LOWER NEW ENGLAND. STRONG LOW-LEVEL
CONVERGENCE IN CONJUNCTION WITH SUFFICIENT INSTABILITY HAS HELPED
CARRY SURFACE PARCELS TO OVER 30 KFT. GIVEN THE BEST INSTABILITY
RESIDES RIGHT ALONG THE COASTLINE...NOT SURE HOW WELL THE BANDS OF
PRECIPITATION WILL STAY INTACT AS THEY PROPAGATE FARTHER INLAND
INTO THE COOLER CONTINENTAL AIR. THUS...THE BEST THREAT FOR FLASH
FLOODING WILL BE WITH THE SLOW-MOVING PRECIPITATION CORES ALONG
THE NJ COAST. THIS FORECAST HAS SUFFICIENT SUPPORT FROM THE
MESOSCALE GUIDANCE...PARTICULARLY THE 07Z HRRR/RAP AND 00Z HRW ARW
AND NMM-B. WILL ALLOW DAY SHIFT TO REASSESS THE SITUATION AFTER
MPD EXPIRATION.


RUBIN-OSTER

...PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...OKX...PHI...

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

LAT...LON   41117391 41017345 40657340 39987362 39557386
            39007450 38937504 39067561 39257584 39577573
            39727513 39907485 40357458 40767435 41027418




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