Flash Flood Guidance
Issued by NWS

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000
AWUS01 KWNH 302101
FFGMPD
CTZ000-NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-310200-

MESOSCALE PRECIPITATION DISCUSSION 0506
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
500 PM EDT SAT JUL 30 2016

AREAS AFFECTED...PORTIONS OF THE NRN MID-ATLANTIC REGION INTO SRN
NEW YORK

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

VALID 302100Z - 310200Z

SUMMARY...AN INCREASING FLASH FLOOD THREAT WILL DEVELOP THROUGH
THE REMAINDER OF THE EVENING WITH BACKBUILDING CONVECTION POSSIBLY
BECOMING MORE NUMEROUS THROUGH 00Z. ONE HOUR RAINFALL RATES OF 2-3
IN/HR CAN BE EXPECTED.

DISCUSSION...REGIONAL RADAR IMAGERY AS OF 2030Z SHOWED WIDESPREAD
CONVECTION FROM NRN VIRGINIA...THROUGH ERN PENNSYLVANIA INTO SRN
NEW YORK. INDIVIDUAL CELLS WERE TRACKING TOWARD THE NE AT 10-15
KTS...ALTHOUGH A FEW CELLS...SUCH AS ONE IN MERCER AND MIDDLESEX
COUNTIES IN NEW JERSEY...HAVE BEEN NEARLY STATIONARY OR
BACKBUILDING WITH RAINFALL RATES OF 2-3 IN/HR. AREA PRECIPITABLE
WATER VALUES OF 2.25 INCHES PER NEARBY GPS SITES AND INSTABILITY
OF 1000-2000 J/KG IS REPRESENTATIVE OF THE CURRENT ENVIRONMENT.

AREA VAD WINDS INDICATE 850-700 MB MEAN FLOW IS SLIGHTLY STRONGER
BETWEEN LOW PRESSURE IN W-CNTRL PENNSYLVANIA AND HIGH PRESSURE
LOCATED SOUTH OF NEW ENGLAND...WITH WINDS FUNNELING IN BETWEEN
THESE TWO FEATURES AT 20-30 KTS OVER ERN PENNSYLVANIA. RAP
FORECASTS INDICATE MAINTENANCE OR A SLIGHT INCREASE TO THIS FLOW
THROUGH 01Z. THE AREA OF GREATEST CONCERN IS FROM NRN MARYLAND
INTO SERN PENNSYLVANIA INTO NEW JERSEY WHERE CONVECTIVE
OVERTURNING HAS NOT YET OCCURRED. WHILE FLASH FLOOD GUIDANCE IS
RELATIVELY HIGH AREA WIDE...POCKETS OF 1.5-2.5 IN/HR FFG EXIST
NEAR AND AROUND URBAN LOCATIONS AND OVER NERN MARYLAND INTO
DELAWARE AND SRN NEW JERSEY WHERE 200-400 PERCENT OF NORMAL
RAINFALL HAS BEEN OBSERVED OVER THE PAST 2 WEEKS. FARTHER
NORTH...WEAK RIGHT ENTRANCE REGION DYNAMICS MAY HELP MAKE UP FOR
WEAKER INSTABILITY TOWARDS SRN NEW YORK INTO WRN CONNECTICUT. THE
ENTIRE REGION FROM NRN VIRGINIA TO WRN CONNECTICUT HAS THE
POTENTIAL FOR POCKETS OF FLASH FLOODING OVER THE NEXT 5 HOURS
BEFORE LOSS OF DAYTIME HEATING LIKELY WANES THE ONGOING THREAT.

OTTO

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

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

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

LAT...LON   41857378 41767290 41687259 41597249 41357244
            41117282 40777333 40197383 39447470 38697592
            38577659 38447747 38687826 39397820 40137729
            41047610 41657496


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