Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 270057
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
857 PM EDT MON SEP 26 2016

...VALID 01Z TUE SEP 27 2016 - 12Z TUE SEP 27 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
50 N MMIO 45 NE MMMV 40 SSE MMPG 20 NE COT 35 N VCT 10 S JAS
15 NNE KXIH 20 ENE 2R8 20 SSW BKS 55 SSW MMRX.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 ESE LYH 10 NW AVC 15 SE RDU 30 NE DNL 25 SSW GRD 20 S EHO
RUQ 25 NNE MTV 20 ESE LYH.


01 UTC UPDATE...

MADE ADDITIONAL CHANGES TO BOTH PREVIOUSLY HIGHLIGHTED AREAS BASED
UPON CURRENT SATELLITE/RADAR TRENDS AND GUIDANCE FROM THE LATEST
RUNS OF THE HRRR.  BIGGEST CHANGE WAS ACROSS THE CAROLINAS AND
SOUTHERN VA WHERE THE MARGINAL RISK WAS SHIFTED EAST OF THE
MOUNTAINS INTO THE PIEDMONT REGION.  CONVECTION THAT DEVELOPED
WEST OF THE REGION EARLIER IN THE EVENING IS GRADUALLY MOVING EAST
INTO A REGION OF LOWER FLASH FLOOD GUIDANCE VALUES...SUGGESTING A
LOCALLY ENHANCED THREAT FOR FLASH FLOODING OVER THE NEXT FEW
HOURS.  REFER TO WPC MPD #707 FOR FURTHER DETAILS CONCERNING THE
THREAT FOR HEAVY RAIN AND THE POTENTIAL FOR FLASH FLOODING ACROSS
WESTERN INTO CENTRAL NC.


PREVIOUS DISCUSSION...

1900 UTC UPDATE

SOUTH TX

CHANGES TO THE PREVIOUS EXCESSIVE RAINFALL POTENTIAL OUTLOOK WERE
TO REMOVE THE SLIGHT RISK AREA OVER SOUTH CENTRAL TX.  THE SURFACE
FRONTAL BOUNDARY CURRENTLY OVER SOUTH TX WILL BE PUSHING SLOWLY
SOUTHWARD TONIGHT INTO EARLY TUESDAY.  WHILE PW VALUES ARE
EXPECTED TO REMAIN ABOVE AVERAGE IN THE VICINITY OF THIS FRONT
OVER SOUTH TX THIS PERIOD---MODEL CONSENSUS IS FOR DECREASING
PRECIPITATION POTENTIAL FOR SOUTH TX AND A SOUTHWARD SHIFT IN THE
AXIS OF THE HEAVIEST PRECIP POTENTIAL TO ALONG THE IMMEDIATE SOUTH
TX COAST AND INTO FAR NORTHEAST MEXICO.  WITH THE EXPECTED
DECREASE IN AREAL COVERAGE AND INTENSITY OF PRECIPITATION---THE
EXCESSIVE RAINFALL THREAT OVER SOUTH CENTRAL TO SOUTH TX ALSO
EXPECTED TO DECREASE.  THE PREVIOUS SLIGHT RISK AREA WAS TAKEN
OUT---WITH A BROAD MARGINAL RISK AREA MAINTAINED.

SOUTHERN APPALACHIANS

OVER THE SOUTHERN APPALACHIANS--A MARGINAL RISK AREA WAS ADDED FOR
ENHANCING CONVECTION CURRENTLY ALONG AND AHEAD OF THE FRONT
PUSHING INTO THIS REGION. FAVORABLE UPPER DIFFLUENCE AND WELL
DEFINED FRONTAL CONVERGENCE IN AN AXIS OF ABOVE AVERAGE PW VALUES
ALONG AND AHEAD OF THIS FRONT WILL SUPPORT HEAVY RAINFALL
POTENTIAL OVER THE NEXT FEW HOURS IN THE VICINITY OF THE SOUTHERN
APPALACHIANS.  WHILE FFG VALUES ARE HIGH ACROSS THIS
REGION---HEAVY DOWNPOURS OF 1"+ IN AN HOUR OR LESS MAY PRODUCE
ISOLATED RUNOFF ISSUES OVER THE HIGHER TERRAIN AREAS.

PEREIRA/ORAVEC
$$




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