Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 301411
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1010 AM EDT SAT AUG 30 2014

...VALID 15Z SAT AUG 30 2014 - 12Z SUN AUG 31 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 NNW PTN 10 WSW P92 30 WSW P92 15 ENE KVNP 10 NW KVNP 7R5
20 NNW KVBS 15 SW BPT 25 SSE JAS 15 NNW POE 10 ESE ESF
25 ENE LFT 10 NNW PTN.


1400 UTC UPDATE

CHANGES TO THE PREVIOUS EXCESSIVE RAINFALL POTENTIAL OUTLOOK
ACROSS LOUISIANA WERE TO EXPAND THE SLIGHT RISK AREA EASTWARD
ACROSS SOUTHERN LA.  THIS IS TO ACCOUNT FOR THE HI RES ARW---NSSL
WRF---CMC GEM AND NAM CONEST WHICH ALL SHOW POTENTIAL FOR VERY
HEAVY RAINFALL AMOUNTS BUILDING EASTWARD THIS PERIOD.

ACROSS THE MID TO LOWER TX GULF COAST---CONCERNS FOR LOCALLY VERY
HEAVY RAINFALL AMOUNTS THIS PERIOD IN THE VICINITY OF THE MID
LEVEL CIRCULATION OVER THE WESTERN GULF OF MEXICO THAT IS NOT
EXPECTED TO MOVE MUCH THIS PERIOD.  NOT A LOT OF CONFIDENCE IN THE
EVOLUTION OF CONVECTIVE MAXIMUM THAT HAVE BEEN ENHANCING NEAR THIS
CENTER.  HOWEVER---WITH THIS FEATURE NOT MOVING MUCH AND REMAINING
IN AN AXIS OF MUCH ABOVE AVERAGE PW VALUES---2.00-2.25"+ ALONG THE
TX GULF COAST---VERY HEAVY RAINFALL AMOUNTS POSSIBLE ALONG THE
IMMEDIATE MID TO LOWER TX GULF COAST.  2-3"+ PRECIPITATION TOTALS
IN AN HOUR OR TWO POSSIBLE WHICH MAY PRODUCE LOCALIZED RUNOFF
ISSUES--ESPECIALLY OVER MORE URBANIZED AREAS.

NORTH CENTRAL ARKANSAS---SOUTHEAST MISSOURI---INTO SOUTHERN
ILLINOIS

CONCERNS FOR VERY HEAVY TO ISOLATED EXCESSIVE RAINFALL AMOUNTS ARE
WITH CONVECTION THAT IS BEGINNING TO TRAIN IN A SOUTHWEST TO
NORTHEASTERLY DIRECTION FROM NORTH CENTRAL ARKANSAS---ACROSS
SOUTHEASTERN MISSOURI AND INTO SOUTHERN ILLINOIS.  THE LOW LEVEL
FLOW EXPECTED TO REMAIN PARALLEL TO THIS AREA OF PRECIPITATION
INTO THIS AFTERNOON IN A REGION OF ENHANCED UPPER DIFFLUENCE.
ISOLATED 1-2"+ PRECIPITATION TOTALS IN AN HOUR OR TWO POSSIBLE
WHERE TRAINING OF MOST INTENSE CELLS OCCURS--WITH ISOLATED RUNOFF
ISSUES POSSIBLE.

ORAVEC


PREVIOUS DISCUSSION


...LOUISIANA/TEXAS COASTS...

A MID LEVEL CIRCULATION ALONG THE GULF COAST WILL CONTINUE TO BE
THE FOCUS FOR HEAVY TO POTENTIALLY EXCESSIVE RAINFALL. THE AIRMASS
ACROSS THE REGION WAS  QUITE MOIST...SOME 1.5 TO 2+ STANDARD
DEVIATIONS ABOVE THE MEAN AND THE MODELS CONTINUE TO HIGHLIGHT A
PERIOD ON ENHANCED ONSHORE FLOW INTO THE MORNING HOURS.  WHILE
RAINFALL RATES MAY BE QUITE IMPRESSIVE...HOW LONG THOSE RAINFALL
RATES PERSIST OVER ONE SPOT MAY OR MAY NOT BE ENOUGH TO REACH
FLASH FLOOD GUIDANCE VALUES WHICH ARE QUITE HIGH ACROSS THE
REGION.  THE HIGHER RESOLUTION GUIDANCE SUGGEST ENOUGH BANDING IN
THE PCPN FIELDS AND ENOUGH ONSHORE FLOW TO EXCEED THE FLASH FLOOD
GUIDANCE...WITH THE HRRR BEING THE WETTEST.  CONSEQUENTLY...A
SLIGHT RISK AREA WAS SHOWN.


BANN

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