Quantitative Precipitation Forecast
Issued by NWS

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000
FOUS30 KWBC 201849
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
248 PM EDT WED AUG 20 2014

...VALID 18Z WED AUG 20 2014 - 00Z FRI AUG 22 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 N DTL 15 N SAZ ROS RYV 20 ESE GSH 10 S FDY 20 WNW OSU
25 SW TZR 25 SSE ILN 15 SE LUK 30 WNW CVG 25 WNW EYE VYS MXO
20 W MWM 50 NE PIR 35 NE HEI KD50 35 SE CWIK CYBR 15 SW KGAF
15 N DTL.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
40 WNW GFL 30 ENE UCA 20 SSE UCA 10 E ITH 10 ENE ELM 25 SSE DSV
15 S DSV 15 WSW DSV 25 WNW DSV 25 WSW ROC 15 WNW ROC 20 SSW CWQP
10 S CYGK 15 SW CWGH 10 S CTCK 15 ESE SLK 40 WNW GFL.



NORTHERN PLAINS---UPPER MS VALLEY--MID WEST INTO THE MID TO UPPER
OH VALLEY

MID TO UPPER LEVEL HEIGHT FALLS EJECTING EAST NORTHEASTWARD FROM
THE NORTHERN HIGH PLAINS TONIGHT INTO THE UPPER MS VALLEY DURING
THE DAY ON THURSDAY WILL SUPPORT INCREASING CONVECTIVE ACTIVITY
FROM THE NORTHERN PLAINS---SOUTHEASTWARD ALONG AND TO THE NORTH OF
A WARM FRONTAL BOUNDARY EXTENDING INTO THE UPPER MS VALLEY---MID
WEST INTO THE OH VALLEY REGION.  PW VALUES AHEAD OF THESE HEIGHT
FALLS AND IN THE VICINITY OF THIS FRONT WILL BE RISING TO MUCH
ABOVE NORMAL--- 2 TO 2.5+ STANDARD DEVIATIONS ABOVE THE MEAN AS
LOW LEVEL SOUTHERLY TO SOUTH WESTERLY FLOW STRENGTHENS INTO THIS
BOUNDARY.  OVERALL THERE IS FAIRLY GOOD AGREEMENT WITH THE QPF
AXES IN THE MODELS.  THE 1200 UTC AUG 20 ECMWF DID TREND SOUTHWARD
FROM ITS 0000 UTC RUN OVER THE UPPER MS VALLEY AND IS CLOSER NOW
TO THE FAVORED AXES OF THE HI RES ARW---NMM AND NSSL WRF WHICH
WERE USED PRIMARILY FOR QPF DETAILS.  HEAVY TO ISOLATED EXCESSIVE
PRECIPITATION TOTALS POSSIBLE IN A NARROW AXIS IN THE VICINITY OF
THIS WARM FRONT.  THE BIGGEST CONCERNS ARE FOR CHANGES IN THE
NARROW QPF AXIS WHICH IS POSSIBLE IF ANY ORGANIZED CONVECTION
PUSHES FARTHER TO THE SOUTH AND SOUTHEAST THAN EXPECTED AT THE
PRESENT TIME.  TRAINING OF CELLS ALONG AND NORTH OF THIS FRONT
POSSIBLE--ESPECIALLY EARLY THURSDAY MORNING WHEN THE LOW LEVEL
FLOW WILL BECOME MORE WEST SOUTHWESTERLY INTO THE FRONT--WITH
ISOLATED SHORT TERM PRECIPITATION TOTALS OF 2"+ POSSIBLE WHERE
TRAINING OCCURS.

WESTERN TO NORTHERN NEW YORK STATE

CONCERNS FOR ISOLATED EXCESSIVE RAINFALL AMOUNTS WILL BE AHEAD OF
THE SURFACE FRONTAL BOUNDARY CURRENTLY MOVING THROUGH THE GREAT
LAKES THAT IS EXPECTED TO MOVE ONLY SLOWLY EASTWARD THIS PERIOD AS
IT ENCOUNTERS BLOCKING FLOW AHEAD OF IT ACROSS SOUTHEAST CANADA.
HIGH PW VALUES---1.50-1.75"+--- AHEAD OF THIS SLOW MOVING FRONT
WILL SUPPORT HEAVY PRECIPITATION AMOUNTS FROM THE NORTHERN MID
ATLANTIC INTO THE SOUTHERN TIER OF NY AND NORTHERN NY.  THE SLOW
MOVEMENT OF THE FRONT WILL ALSO POSE RUNOFF ISSUES FOR PORTIONS OF
WESTERN NY/SOUTHERN TIER OF NY INTO NORTHERN NY WHERE THERE ARE
RELATIVELY LOW FFG VALUES.  SHORT TERM PRECIPITATION TOTALS OF
1-2"+ POSSIBLE IN AREAS OF SLOW MOVING CONVECTION.


ORAVEC
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