Quantitative Precipitation Forecast
Issued by NWS

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000
FOUS30 KWBC 270655
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
154 AM EST SAT DEC 27 2014

...VALID 06Z SAT DEC 27 2014 - 12Z SUN DEC 28 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 W KCRH 20 ESE BPT 15 WNW LCH 20 SW TVR 25 ESE UTA 15 NW MKL
45 NE MKL 55 ENE MKL 35 NNW MSL 10 E MSL 20 NE 1M4 25 ESE 1M4
20 NNW BHM 20 WSW GAD 25 E GAD 10 SSW VPC ATL 30 S AUO NPA
20 SSW KMIS 10 W KMDJ 10 ESE GSM 20 SW KEIR 10 NE KVQT 25 W KCRH.


LOWER MISSISSIPPI VALLEY TOWARD THE TN VALLEY

THE PREVIOUS SLIGHT RISK AREA OVER THE LOWER MS VALLEY REGION WAS
EXPANDED NORTHEASTWARD TOWARD THE TN VALLEY REGION ACROSS THE
MODEL CONSENSUS AREA FOR POTENTIALLY VERY HEAVY TO EXCESSIVE
RAINFALL AMOUNTS.  INCREASING COVERAGE AND INTENSITY OF
PRECIPITATION EXPECTED THIS PERIOD FROM THE LOWER MS VALLEY TOWARD
THE TN VALLEY ALONG AND AHEAD OF A SLOWLY EASTWARD MOVING FRONTAL
BOUNDARY.  PW VALUES EXPECTED TO CONTINUE TO RISE TO 2-2.5+
STANDARD DEVIATIONS ABOVE THE MEAN IN THE STRENGTHENING
SOUTHWESTERLY LOW LEVEL FLOW AHEAD OF THIS FRONT.  THIS WILL BE IN
A FAVORABLE RIGHT ENTRANCE REGION OF THE UPPER JET--SUPPORTING THE
MODEL CONSENSUS FOR WIDESPREAD HEAVY TOTALS ACROSS THESE AREAS.
THERE CONTINUES TO BE SOME MODEL DIFFERENCES WITH RESPECT TO THE
AXIS OF THE HEAVIEST RAINFALL AMOUNTS.  THE GFS---GFSP AND THE
1200 UTC ECMWF ARE ON THE FARTHER SOUTH SIDE OF THE
GUIDANCE---WITH THE NAM AND HI RES ARW AND NMMB FARTHER NORTH.
THE FARTHER SOUTH AXIS WAS PREFERRED---WHICH HAS SUPPORT IN THE
REFORECAST QPF.  THERE MAY BE A PERIOD OF TRAINING OF CELLS IN THE
PERSISTENT SOUTHWEST LOW LEVEL FLOW FROM SATURDAY AFTERNOON INTO
THE EARLY HOURS OF SUNDAY.  IN AREAS OF TRAINING---VERY HEAVY
RAINFALL AMOUNTS AND RUNOFF ISSUES ARE POSSIBLE---WITH ISOLATED
TOTALS OF 3-5"+ POSSIBLE.

ORAVEC

$$





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