Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 290816
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
315 AM EST TUE NOV 29 2016

...VALID 12Z TUE NOV 29 2016 - 12Z WED NOV 30 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 W KCMB 30 WNW CBM 25 WSW CSV TYS 15 NE WDR 10 SE LGC
25 SW TOI 15 N AXO 25 SW SRN 10 W KCMB.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 NE BID FOK 10 NNW BLM PHL DMH 15 ENE FDK 20 NE FDK
10 SSW THV 15 SSE MPO BDL 10 WSW OWD 25 N PVC 15 N PVC
10 NNE FMH 10 NE BID.


URBAN CORRIDOR FROM BALTIMORE---NYC TO BOSTON

THE EMPHASIS FOR HEAVY RAINFALL BY THE BEGINNING OF THIS FORECAST
PERIOD...1200 UTC TUESDAY---SHOULD BE SHIFTING FROM THE SOUTHEAST
INTO THE MID ATLANTIC--NORTHEAST AND SOUTHERN NEW ENGLAND.  THE
CONSENSUS FROM THE HI RES SIMULATED RADARS IS FOR THE STRONGEST
RADAR ECHOES---CENTERED OVER THE SOUTHEASTERN U.S. EARLY THIS
MORNING---WEAKENING SHORTLY AFTER 1200 UTC---WITH THE EMPHASIS FOR
THE HEAVIEST PRECIP/STRONGEST ECHOES REFOCUSING FARTHER
NORTHEASTWARD FROM THE MID ATLANTIC INTO THE NORTHEAST AND
ENGLAND.  THIS SEEMS REASONABLE GIVEN THE FAST NORTHEAST MOVEMENT
OF THE MID TO UPPER LEVEL SHORTWAVES AND THE NORTHEAST PUSH OF THE
STRONGEST UPPER DIFFLUENCE/MOST CONCENTRATED AREA OF WELL DEFINED
UVVS.   OVERALL THERE IS GOOD AGREEMENT MASS FIELD WISE AMONG THE
LATEST SUITE OF MODELS AND FAIRLY GOOD AGREEMENT WITH THE
WIDESPREAD AXIS OF MODERATE TO HEAVY TOTALS.   THERE IS CONSENSUS
IN MUCH OF THE GUIDANCE FOR MAX PRECIP TOTALS DAY 1 FROM IN THE
VICINITY OF NORTHERN MD/SOUTHEASTERN PA---ACROSS MUCH OF
NJ---SOUTHEAST NY-NYC METRO AREA AND INTO SOUTHERN NEW ENGLAND.
THERE COULD BE A PERIOD OF TRAINING OR SLOW MOVEMENT OF CELLS IN A
GENERAL SOUTHWEST TO NORTHEASTERLY DIRECTION ACROSS THESE REGIONS.
 WHILE THESE AREAS HAVE BEEN VERY DRY AND FFG VALUES ARE
HIGH---ISOLATED RUNOFF ISSUES MAY DEVELOP IN AREAS OF
TRAINING---ESPECIALLY ACROSS THE URBAN CORRIDOR FROM
DC/BALTIMORE---INTO PHL---NYC AND BOS.  OVERALL FOR THE UPCOMING
FORECAST PERIOD...AREAL AVERAGE .50-1"+ AMOUNTS POSSIBLE ACROSS
THESE AREAS---WITH ISOLATED TOTALS OF 2-4" WHERE TRAINING OCCURS.

LOWER MS VALLEY---MID TO UPPER TN VALLEY INTO THE SOUTHERN
APPALACHIANS

ADDITIONAL HEIGHT FALLS ROTATING THROUGH THE BASE OF THE MEAN TROF
ACROSS THE MID SECTION OF THE NATION WILL HELP STRENGTHEN THE
SOUTHWEST LOW LEVEL FLOW OFF THE GULF---SUPPORTING A SECOND
NORTHEASTWARD SURGE OF MUCH ABOVE AVERAGE PW VALUES FROM THE
CENTRAL GULF COAST---INTO THE TN VALLEY AND CENTRAL TO SOUTHERN
APPALACHIANS.  PRECIP SHOULD INCREASE IN COVERAGE AND INTENSITY
TUESDAY EVENING/NIGHT INTO THE EARLY HOURS OF WEDNESDAY ALONG AND
AHEAD OF THE ASSOCIATED SECONDARY FRONTAL BOUNDARY IN THE AXIS OF
MUCH ABOVE AVERAGE PW VALUES---STRONG FRONTAL CONVERGENCE AND WELL
DEFINED UPPER DIFFLUENCE.  WHILE MODELS AGREE ON THE OVERALL
SCENARIO---THERE ARE DIFFERENCES WITH THE QPF AXES AMONG THE
MODELS.  THE NAM IS THE FARTHEST TO THE NORTHWEST--WITH NEARLY ALL
OF THE REMAINING GUIDANCE SUPPORTING A FARTHER SOUTHEASTWARD AXIS.
 WPC QPF FAVORED THE MAJORITY AXIS SOLUTION---WITH DETAILS CLOSEST
TO THE HI RES ARW AND HI RES ENSEMBLE MEANS.  ADDITIONAL HEAVY
PRECIP TOTALS POSSIBLE ACROSS PORTIONS OF THE CENTRAL GULF
COAST/LOWER MS VALLEY INTO THE MID TO UPPER TN VALLEY AND SOUTHERN
APPALACHIANS THAT HAVE RECEIVED HEAVY RAINFALL EARLIER TODAY.
OVER THESE AREAS---A MARGINAL RISK WAS MAINTAINED FOR POTENTIAL OF
ISOLATED ADDITIONAL TOTALS OF 1-2".


ORAVEC

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