Flash Flood Guidance
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000
AWUS01 KWNH 030027
FFGMPD
NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-030401-

MESOSCALE PRECIPITATION DISCUSSION 0171
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
826 PM EDT MON MAY 02 2016

AREAS AFFECTED...BETWEEN D.C. AND PHILADELPHIA PA

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

VALID 030026Z - 030401Z

SUMMARY...A GROWING CLUSTER OF THUNDERSTORMS AROUND THE D.C.
SUBURBS COULD LEAD TO CELL TRAINING BEFORE THUNDERSTORMS WEAKEN BY
04Z.

DISCUSSION...A MESOSCALE FRONTAL WAVE NEAR THE MD/WV/VA BORDER
JUNCTION HAS A SHORT WARM FRONT EXTENDING INTO NORTHERN VA.  WHILE
CLOUD TOPS HAVE BEEN COOLING LATELY ON SATELLITE IMAGERY, RADAR
INDICATIONS LATELY HAVE BEEN SLIGHTLY DOWNWARD.   THE LATEST SPC
MESOANALYSIS INDICATES DEVELOPING CIN, WHICH WOULD HELP EXPLAIN
THE NEW THUNDERSTORM ACTIVITY IN SOUTHEAST PA.  PRECIPITABLE WATER
VALUES ARE 1.3-1.4" IN THIS AREA, WHILE MUCAPES ARE ~1500 J/KG.
INFLOW AT 850 HPA IS ~25 KTS, WHILE BULK SHEAR VALUES IN THE 0-6
KM LAYER ARE 50-55 KTS, WHICH IS ALSO HELPING TO ORGANIZE
THUNDERSTORM ACTIVITY.

INSTABILITY SHOULD CONTINUE TO WANE OVER THE NEXT FEW HOURS DUE TO
THUNDERSTORM ACTIVITY AND THE LOSS OF DAYTIME HEATING.  UNTIL
03-04Z, EXPECT HOURLY RAIN RATES UP TO 1.5" WHERE CELL MERGERS AND
SHORT PERIODS OF CELL TRAINING OCCUR, WHICH PER THE CAM/MESOSCALE
GUIDANCE COULD LEAD TO ANOTHER 2-3" LOCALLY.  THIS COULD
POTENTIALLY LEAD TO FLASH FLOODING WITHIN THE URBAN CORRIDOR
BETWEEN WASHINGTON D.C. AND PHILADELPHIA, PA.

ROTH

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

ATTN...WFO...AKQ...CTP...LWX...PHI...

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

LAT...LON   40447537 40227455 39637432 38747487 38497568
            38527703 38717750 39527783 39527785 40227660




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