Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 300812
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
411 AM EDT SAT APR 30 2016

...VALID 12Z SAT APR 30 2016 - 12Z SUN MAY 01 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
W99 25 W SHD 20 SSE HSP BCB 10 NNE MKJ VJI 20 W TRI 10 W EKQ
25 E GLW 25 SSW OWB EHR 20 WNW HNB 30 NNE HNB 10 NW CVG
35 ESE ILN UNI 10 NW PKB 25 ENE PKB 20 S AFJ 15 NE MGW 20 S 2G4
W99.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 E SRN 10 NNE KCRH 35 W KCRH 25 S KXIH 25 SE LBX 15 NW LBX
10 WSW DWH 15 SE UTS 35 NE OCH 25 WSW LLQ 35 E PBF 35 WSW UTA
25 SSE UTA 40 SSE UTA 45 SE UTA 40 ESE GWO 35 SW MEI PIB
20 S HBG 15 E NEW 2GL 25 E SRN.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 SSW HEZ 25 NNW BTR 15 N BTR 15 ENE BTR 25 SE BTR 30 NNE 7R3
10 NNW PTN 15 E 7R4 15 ENE KCMB KVBS 15 WSW BPT 30 WNW POE
25 ENE IER 25 NE ESF 35 SSW HEZ.


FAR SOUTHEAST TX INTO THE LOWER MS VALLEY

THERE IS UNCERTAINTIES WITH RESPECT TO THE EVOLUTION OF THE
CURRENT EXCESSIVE RAINFALL EVENT ACROSS SOUTHEAST TX---NW LA INTO
PORTIONS OF ARKANSAS AS THE NEW DAY 1 EXCESSIVE PERIOD BEGINS AT
1200 UTC.  TIMING OF THE EAST SOUTHEAST MOVEMENT OF THE ORGANIZED
AREA OF CONVECTION DIFFERS AS DOES HOW FAR TO THE SOUTH THE
CONVECTION BUILDS INTO SOUTHEAST TX---BUT THERE IS GENERAL
AGREEMENT THAT THERE WILL BE INCREASED PROGRESSION BY OR SHORTLY
AFTER 1200 UTC.  THE STRONG SOUTH SOUTHWESTERLY LOW LEVEL FLOW
THAT HAS PERSISTED OVER PORTIONS OF NORTHEAST TO SOUTHEAST TX IS
FORECAST TO BEGIN TO VEER TO A MORE SOUTHWESTERLY DIRECTION AND
SUPPORT INCREASED DOWNSTREAM PROGRESSION OF THE CONVECTION.
WHETHER THIS OCCURS PRIOR TO OR SHORTLY AFTER 1200 UTC WILL
DETERMINE THE WESTERN EDGE OF THE RISK AREA.  THE LAST FEW RUNS OF
THE HRRR HAVE BEEN CONSISTENT IN SHOWING THE HEAVY RAIN THREAT
REACHING THE HOUSTON AREA IN THE 1200 TO 1800 UTC TIME
FRAME---WITH THE SLIGHT RISK AREA EXTENDED SOUTHWESTWARD TO COVER
THIS POTENTIAL.  WHILE OVERALL INCREASED PROGRESSION EXPECTED THIS
PERIOD--- TRAINING OF CELLS IN A SOUTHWEST TO NORTHEASTERLY
DIRECTION POSSIBLE---ESPECIALLY AT THE BEGINNING OF THIS
PERIOD---FROM SOUTHEAST TX INTO SOUTHWEST LA.  THIS IS THE REGION
DEPICTED WITH A MODERATE RISK--WITH SHORT TERM PRECIP TOTALS OF
2"+ POSSIBLE IN AREAS OF TRAINING.  WITH THE EXPECTED INCREASED
PROGRESSION---THE EXCESSIVE THREAT SHOULD BEGIN TO DIMINISH BY
AFTERNOON AS THE ORGANIZED AREA OF CONVECTION PUSHES EASTWARD INTO
THE LOWER MS VALLEY.

OH VALLEY INTO THE CENTRAL APPALACHIANS

WHILE THE HEAVY TO EXCESSIVE RAINFALL THREAT SHOULD BEGIN TO
DIMINISH LATE AFTERNOON ACROSS THE LOWER MS VALLEY---IT WILL BE ON
THE INCREASE ACROSS THE OH VALLEY INTO THE CENTRAL APPALACHIANS AS
THE BEST UPPER DIFFLUENCE TO THE EAST OF THE CENTRAL PLAINS CLOSED
LOW LIFTS NORTHEASTWARD.  A FAIRLY BROAD SLIGHT RISK AREA WAS
DEPICTED OVER THE OH VALLEY INTO THE CENTRAL APPALACHIANS TO COVER
THE SPREAD IN THE MODEL QPF DETAILS.  WHILE THERE ARE DIFFERENCES
AMONG THE MODELS WITH RESPECT TO THE AXIS OF THE HEAVIEST
PRECIPITATION TOTALS ACROSS THE OH VALLEY INTO THE CENTRAL
APPALACHIANS DUE TO TIMING DETAIL DIFFERENCES---THERE IS A STRONG
MODEL SIGNAL FOR HEAVY TO ISOLATED EXCESSIVE RAINFALL TOTALS
ACROSS THE OH VALLEY INTO THE CENTRAL APPALACHIAN REGION.  WHILE
CONVECTION IS EXPECTED TO BE PROGRESSIVE ACROSS THESE AREAS---LOW
FFG VALUES WILL SUPPORT ISOLATED RUNOFF ISSUES WHERE CONVECTION
BECOME MOST ORGANIZED---WITH SHORT TERM 1-1.5"+ PRECIP TOTALS
POSSIBLE.

ORAVEC
$$





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