Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 210255
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1054 PM EDT WED MAY 20 2015

...VALID 0254Z THU MAY 21 2015 - 12Z THU MAY 21 2015...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
65 N MMMV 50 SSE 6R6 40 ENE 6R6 20 E E29 25 SE JCT 25 NNE COT
40 ESE COT 25 SSW BKS 25 W MFE 50 ENE MMMY 40 NNE MMAN
45 NNE MMMV 65 N MMMV.



...PORTIONS OF WEST/CENTRAL/SOUTH TEXAS...

0245Z UPDATE...ONLY MINOR CHANGES TO PREVIOUS OUTLOOK PULLING
SLIGHT RISK AREA FARTHER EAST TO INCLUDE A BIG MORE OF THE HILL
COUNTRY AND SOUTH TX...INCLUDING AUS AND SAT...TO ACCOUNT FOR THE
DEVELOPING MCS OVER WEST TX. OTHERWISE...PREVIOUS FCST REASONING
STILL VALID.  LATE WEDNESDAY NIGHT INTO EARLY THURSDAY---CONCERNS
FOR HEAVY TO POSSIBLY ISOLATED EXCESSIVE RAINFALL AMOUNTS SHIFT TO
THE VICINITY OF THE BIG BEND AND SOUTHEASTWARD INTO THE LOWER RIO
GRANDE.  SHORTWAVE ENERGY MOVING OUT OF NORTHERN MEXICO ON THE
SOUTHERN EDGE OF THE WESTERLIES MAY IGNITE MORE ORGANIZED
CONVECTION NEAR THE BIG BEND---WITH THIS ACTIVITY THEN PUSHING
SOUTHEASTWARD ALONG THE RIO GRANDE IN THE EARLY HOURS OF THU.
THERE IS SUPPORT FOR THIS SOLUTION IN THE HI RES
ARW--NMMB---ECMWF---NAM CONEST AND CMC GEM---ALTHOUGH THEY DO
DIFFER WITH RESPECT TO HOW FAR TO THE SOUTHEAST CONVECTION
PROPAGATES.  WHILE LOW LEVEL MSTR IS HIGH...LOW LEVEL WINDS ARE
NOT EXPECTED TO GET MUCH ABOVE 20 TO 25 KTS OVERNIGHT AND THEN
JUST BRIEFLY...SO NOT LOOKING FOR LARGE SCALE FLOODING POTNL AT
THIS TIME.  THE SLIGHT RISK WAS DRAWN TO ENCOMPASS THE VARYING
GEOGRAPHICAL LOCATIONS OF THE HEAVY RAINFALL FORECASTS IN THE HI
RES RUNS.  HEAVY TO ISOLATED EXCESSIVE RAINFALL AMOUNTS POSSIBLE
WITH THIS CONVECTION IN THE EARLY HOURS OF THURSDAY FROM ISOLATED
SHORT TERM PRECIP TOTALS OF 2-4"+.


SULLIVAN/PETERSEN/ORAVEC/HURLEY
$$




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