Quantitative Precipitation Forecast
Issued by NWS

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000
FOUS30 KWBC 010823
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
421 AM EDT SUN MAY 01 2016

...VALID 12Z SUN MAY 01 2016 - 12Z MON MAY 02 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
TVR 35 NE JAN 20 WNW NMM 20 SE NMM 60 SE MEI PQL 35 NNE 1B7
25 NNE GSM 35 NE KEHC 10 SW KCRH 25 SSE KXIH 20 SSW KXIH
20 WSW GLS HOU 15 NE CXO 30 NNW JAS 25 SSE MLU TVR.


UPPER TX COAST---CENTRAL TO SOUTHERN LA INTO SOUTHWEST MS

THE EXCESSIVE RAINFALL THREAT RETURNS TO PORTIONS OF THE GULF
COAST FROM THE UPPER TX COAST---ACROSS CENTRAL TO SOUTHERN LA AND
INTO SOUTHERN MS.  THE FORECAST BACKING OF THE LOW LEVEL FLOW TO A
MORE SOUTHERLY DIRECTION OFF THE GULF OF MEXICO IS ALREADY FIRING
CONVECTION EARLY THIS MORNING ACROSS THE UPPER TX COAST INTO
SOUTHWEST LA.  CONVECTION LIKELY TO REMAIN ACTIVE ALONG AND TO THE
SOUTHEAST OF THE SLOW MOVING FRONTAL BOUNDARY STRETCHING FROM
SOUTHEAST TX INTO THE LOWER MS VALLEY THIS PERIOD AS THIS MOIST
ONSHORE FLOW PERSISTS ALONG WITH FAVORABLE UPPER DIFFLUENCE
BETWEEN THE EXIT REGION OF AN UPPER JET MOVING ACROSS SOUTH TX AND
THE ENTRANCE REGION OF A JET FARTHER NORTH ACROSS THE SOUTHERN
PLAINS.  THERE IS A MODEL SIGNAL FOR HEAVY TO EXCESSIVE RAINFALL
AMOUNTS ACROSS THESE AREAS---ALTHOUGH THERE IS A LARGE DEGREE OF
SPREAD MODEL TO MODEL AND A LOT OF RUN TO RUN VARIABILITY.
SUBSEQUENLTY---CONFIDENCE IS ON THE LOWER THAN NORMAL SIDE WITH
RESPECT TO THE DETAILS---WITH THE HI RES ENSEMBLE MEANS USED
PRIMARILY---RESULTING IN THE MAX AXIS FROM SOUTHERN MS---ACROSS
SOUTHERN LA AND INTO THE UPPER TX COAST. THE 0000 HI RES ARW AND
NSSL WRF EXEMPLIFY THE SIGNIFICANT RUN TO RUN VARIABILITY---BOTH
SHOWING CONVECTION FORMING OVER THE UPPER TX COAST/SOUTHERN LA
THIS MORNING PUSHING OFFSHORE BY LATE AFTERNOON.  THIS WAS A
SIGNIFICANT CHANGE IN CONTINUITY IN BOTH MODELS AND IS NOT
SUPPORTED BY THE LATEST HRR RUNS.    WITH THE RECENT VERY HEAVY
RAINFALL EVENT OVER PORTIONS OF SOUTHEAST TX INTO SOUTHERN LA
HAVING LOWERED FFG VALUES----ADDITIONAL RUNOFF ISSUES ARE POSSIBLE
FROM SLOW MOVING CELLS THAT PRODUCE 1-2"+ PRECIP TOTALS IN A SHORT
PERIOD.  PLEASE SEE WPC`S MESOSCALE PRECIPITATION DISCUSSION #0158
VALID FROM 0900-1500 UTC FOR ADDTIONAL SHORT TERM INFORMATION
ACROSS PORTIONS OF THIS RISK AREA.

OVER THE CENTRAL APPALACHIANS

HI RES MODEL CONSENSUS ON TIMING OF THE CURRENT AREA OF MODERATE
TO HEAVY RAINS AFFECTING THE CENTRAL APPALACHIANS IS FOR IT TO BE
PUSHING EAST OF THE CENTRAL APPALACHIANS SHORTLY AFTER THE
BEGINNING OF THIS FORECAST PERIOD...12000 UTC SUNDAY.  RAINFALL
RATES OF .50-1" PER HOUR MAY LINGER OVER THE CENTRAL APPALACHIANS
FOR THE FIRST 1-3 HOURS OF THIS FORECAST PERIOD---WITH ISOLATED
RUNOFF ISSUES POSSIBLE.  ADDITIONAL SCATTERED CONVECTION POSSIBLE
LATER THIS AFTERNOON ACROSS THIS REGION---BUT NOT EXPECTED TO BE
AS ORGANIZED AS THE CURRENT ACTIVITY.

ORAVEC
$$





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