Quantitative Precipitation Forecast
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031
FOUS30 KWBC 031436
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
935 AM EST WED FEB 03 2016

...VALID 15Z WED FEB 03 2016 - 12Z THU FEB 04 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 WNW MFV 10 ENE JNX 35 SSE SSC 10 ESE LHW 10 SW CTY 110 S AAF
65 ENE KIPN 20 S KVOA 35 SW JKA 25 SW GZH 15 ENE ALX 20 WNW 47A
15 ESE TYS 25 WSW LNP 30 WNW I16 25 WNW W22 25 SW LBE 20 NE DUJ
10 ENE DSV 15 SW ART 20 W SLK 25 S MPV 15 ENE BML WVL IWI
10 N BVY GON 20 E BLM 20 WNW MFV.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 SE VLD 10 SW 40J 40 SSE AAF 70 SSW PAM 35 S DTS 30 N ECP
20 N 11J 40 N ABY 20 S EZM 15 SSE DQH 15 SE VLD.


1500 UTC UPDATE

THERE WERE ONLY SOME MINOR CHANGES MADE TO THE PREVIOUS EXCESSIVE
RAINFALL POTENTIAL OUTLOOK STRETCHING FROM THE FL
PANHANDLE...NORTHEASTWARD INTO UPSTATE NY AND SOUTHWEST NEW
ENGLAND.  THE WESTERN EDGE WAS TRIMMED AS PER THE LATEST RADAR
TRENDS WHERE PRECIPITATION IS COMING TO AN END.  OTHERWISE...NO
CHANGES FOR AREAS DOWNSTREAM AND NO CHANGES TO THE FORECAST
RATIONALE AS STATED BELOW.

ORAVEC

PREVIOUS DISCUSSION

...EASTERN SEABOARD...

ALONG THE EASTERN SEABOARD STRETCHING FROM THE EASTERN GULF COAST
STATES NORTH THROUGH THE MID-ATLANTIC AND NEW ENGLAND...THERE WILL
BE A PATTERN OF MUCH ABOVE AVERAGE PW VALUES ALONG AND AHEAD OF A
SLOW-MOVING COLD FRONT...WHICH ARE FORECAST TO BE 3 TO 4 STANDARD
DEVIATIONS ABOVE THE MEAN OVER BASICALLY THE ENTIRE EASTERN
SEABOARD TO THE EAST OF THE APPALACHIANS. THIS AXIS OF ANOMALOUS
MOISTURE WILL BE COURTESY OF AN IMPRESSIVELY STRONG SOUTHERLY LOW
LEVEL JET WHICH A CONSENSUS OF MODELS INDICATES REACHING AS HIGH
AS 50 TO 70 KTS AHEAD OF THE FRONT AND THUS RESULTING IN EXTREMELY
HIGH MOISTURE FLUX ANOMALIES OF AS MUCH AS 4 TO 5 STANDARD
DEVIATIONS ABOVE NORMAL IN THE 850/700 MB LAYER. WIDESPREAD
MODERATE TO HEAVY RAIN IS EXPECTED WITHIN THIS AXIS OF HIGHER PWS
WHERE CONVERGENT LOW LEVEL FLOW WILL BE COINCIDING WITH A
RELATIVELY DIVERGENT FLOW REGIME ALOFT IN THE 500/300 MB LAYER.
THE GLOBAL MODELS HAVE BEEN CONSISTENTLY UNDERDONE WITH THEIR QPF
FOR THIS EVENT...AND THE 00Z NAM AND 00Z GFS AGAIN APPEAR TO BE
SIMPLY NOT GENERATING ENOUGH HEAVY RAIN GIVEN SUCH ANOMALOUS
MOISTURE TRANSPORT. SOME AREAS ALONG THE EAST COAST MAY APPROACH
OR EXCEED RECORD PW VALUES FOR THE MONTH OF FEBRUARY ON WED...AND
WITH THE SYNOPTIC SET-UP...HEAVY RAINS ARE GUARANTEED OVER A LARGE
AREA OF THE EASTERN SEABOARD. THE NON-NCEP GUIDANCE IS A BIT
WETTER AND ESPECIALLY THE 00Z UKMET...BUT EVEN THESE MODELS HAVE
TENDED TO BE LOCALLY UNDERDONE.

WIDESPREAD 1 TO 2 INCH RAINS ARE ANTICIPATED ACROSS AREAS
INCLUDING THE MID-ATLANTIC AND NORTHEAST...AND ESPECIALLY IN
VICINITY OF HIGH TERRAIN WHERE OROGRAPHIC FORCING WILL BE
ENHANCING RAINFALL RATES. THE HEAVIEST RAINS FOR THE PERIOD THOUGH
ARE EXPECTED TO BE DOWN ACROSS PORTION OF THE SOUTHEAST COASTAL
PLAIN AND INTO THE FL PANHANDLE. PERSISTENTLY CONVERGENT LOW LEVEL
FLOW JUST AHEAD OF THE SLOW-MOVING COLD FRONT COUPLED WITH A MUCH
BETTER DEFINED AXIS OF INSTABILITY WILL PROMOTE ORGANIZED AND
LOCALLY VERY HEAVY CONVECTIVE RAINS HERE WHICH IS STRONGLY
ADVERTISED BY THE 00Z WRF-ARW AND THE 00Z NSSL-WRF SOLUTIONS.
RAINFALL AMOUNTS HERE OF 3 TO 5 INCHES WITH LOCALLY HEAVIER
AMOUNTS ARE POSSIBLE. GIVEN THE HEAVY RAINFALL AMOUNTS OVER
PORTIONS OF THE MID-ATLANTIC AND NORTHEAST WHERE THERE HAS BEEN
ONGOING SNOW-MELT...EXPECT THERE TO BE CONCERNS FOR RUNOFF
PROBLEMS AND FLOODING. ADDITIONAL CONCERNS FOR FLOODING ARE
EXPECTED DOWN ACROSS THE FL PANHANDLE AND INTO SOUTHWEST GA WITH
THE AFOREMENTIONED CONVECTIVE ORGANIZATION THAT IS EXPECTED TO BE
IN PLACE. WILL CONTINUE TO MONITOR.

ORRISON

$$





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