Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 200750
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
349 AM EDT WED MAY 20 2015

...VALID 12Z WED MAY 20 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 S CDS 35 WNW CDS 40 NNW CDS 40 W CSM CSM 20 ESE CSM
20 WNW CHK TIK 15 SSE CQB 15 SE OKM 10 NNE JSV 20 NE FSM
35 ENE FSM 15 NW MWT 15 SW MWT 15 N TXK OSA 10 W 3T1 RBD
10 WSW MWL 35 W RPH 65 S CDS.


FAR SOUTHEAST OK---FAR NORTHEAST TX---SOUTHERN AR AND CENTRAL TX

ONGOING FLASH FLOOD EVENT ALONG THE WEST TO EAST ORIENTED FRONTAL
BOUNDARY IN THE VICINITY OF THE RED RIVER MAY CONTINUE INTO THE
EARLY PORTION OF THE DAY 1 TIME PERIOD ACROSS FAR SOUTHEASTERN
OK---FAR NORTHEASTERN TX INTO SOUTHERN ARKANSAS.  CLOUD TOPS ARE
BEGINNING TO WARM EARLY THIS MORNING WITH THIS CONVECTION---AS PER
LATEST SATELLITE IMAGERY---AND THE LATEST HRRR AND HI RES ARW DO
SHOW A WEAKENING TREND FROM NOW UNTIL SHORTLY AFTER 1200 UTC.  A
SLIGHT RISK WAS MAINTAINED FOR THE POTENTIAL THAT TRAINING OF
CELLS IN A WEST TO EASTERLY DIRECTION MAY CONTINUE FOR A FEW HOURS
AFTER 120O UTC AND PRODUCE ISOLATED SHORT TERM RAINFALL AMOUNTS OF
1-2".   ANY RUNOFF THREAT HERE WILL LIKELY DIMINISH PRIOR TO NOON.
 HOWEVER--CAN NOT RULE OUT ADDITIONAL CONVECTION FIRING FARTHER TO
THE SOUTHWEST LATER THURSDAY ALONG THE SOUTHWARD MOVING COLD FRONT
ACROSS PORTIONS OF CENTRAL TX THAT COULD PRODUCE LOCALLY HEAVY TO
ISOLATED EXCESSIVE RAINS AS MOIST SOUTHERLY INFLOW CONTINUES INTO
THE BOUNDARY.  WITH NO CLEAR MODEL SIGNAL FOR PLACEMENT---NO RISK
AREA IS DENOTED--BUT WITH RECENT RAINS LOWERING FFG VALUES---THIS
AREA WILL NEED TO BE MONITORED.

IN THE VICINITY OF THE BIG BEND---SOUTHEASTWARD INTO THE LOWER RIO
GRANDE

LATE WEDNESDAY NIGHT INTO EARLY THURSDAY---CONCERNS FOR HEAVY TO
POSSIBLY ISOLATED EXCESSIVE RAINFALL AMOUNTS SHIFT TO IN 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.  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"+.

ORAVEC
$$





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