Quantitative Precipitation Forecast
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FOUS30 KWBC 160820
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
319 AM EST SAT DEC 16 2017

...VALID 12Z SAT DEC 16 2017 - 12Z SUN DEC 17 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 SE ACT 15 NNE LBR 20 NNW MWT 20 NW LRF 10 SE SGT 25 SSW LLQ
MLU 15 WNW CWF 20 SW KXIH 15 S PSX 15 E HBV 60 SSE MMNL
15 W MMNL 20 S TPL 25 SE ACT.


EASTERN TEXAS---WESTERN LOUISIANA INTO SOUTHERN ARKANSAS

A BROAD MARGINAL RISK AREA WAS MAINTAINED THIS PERIOD FROM EASTERN
TEXAS INTO WESTERN LOUISIANA AND SOUTHERN ARKANSAS AHEAD OF THE
EJECTING NORTH CENTRAL MEXICO CLOSED LOW.  THIS SYSTEM WILL BE
KICKED NORTHEASTWARD SATURDAY TOWARD THE BIG BEND/SOUTHWEST TX BY
THE DEVELOPING CLOSED LOW OVER NORTHWEST MEXICO.  THE EJECTING
HEIGHT FALLS ARE THEN EXPECTED TO ACCELERATE SATURDAY NIGHT INTO
EARLY SUNDAY INTO NORTHEAST TX---EASTERN OK AND NORTHERN ARKANSAS.
 STRENGTHENING SOUTHERLY LOW LEVEL FLOW OFF THE WESTERN GULF AHEAD
OF THESE HEIGHT FALLS WILL INCREASE PW VALUES TO 1-2 STANDARD
DEVIATIONS ABOVE THE MEAN.  THIS AND FAVORABLE UPPER DIFFLUENCE
AHEAD OF THESE HEIGHT FALLS WILL SUPPORT A BROADENING AREA OF
MODERATE TO HEAVY RAINS ACROSS EASTERN PORTIONS OF THE SOUTHERN
PLAINS TOWARD THE LOWER MS VALLEY.  THE LACK OF INSTABILITY AND
THE PROGRESSIVE NATURE OF THE HEIGHT FALLS SHOULD KEEP PRECIP
TOTALS FROM BEING VERY HEAVY.  MODEL CONSENSUS IS FOR MAX TOTALS
IN THE 1-1.5"+ RANGE OVER EASTERN TX INTO WESTERN LA AND SOUTHERN
ARKANSAS.  WHILE THE MARGINAL RISK AREA IS MAINTAINED FROM
PREVIOUS FORECASTS---THE QUICK MOVEMENT---LACK OF INSTABILITY AND
HIGH FFG VALUES SHOULD KEEP ANY RUNOFF RISK VERY LOW.

ORAVEC
$$





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