Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 180059
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
859 PM EDT SUN MAY 17 2015

...VALID 01Z MON MAY 18 2015 - 12Z MON MAY 18 2015...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
MSL 35 SE MLU 25 NE UTS 40 NE LHB 10 SSW 3T1 20 NE MWT
10 SW MWA 25 WNW BWG MSL.



...MID MS/OH VALLEY CONFLUENCE SOUTHWESTWARD INTO EASTERN TX...

HAVE SCALED BACK THE EXCESSIVE OUTLOOK AREA A BIT IN TX AND
LA...WITH THE CURRENT VERSION VALID FROM 01-12Z NOW ENCOMPASSING
NORTHERN LA AND A SMALL PORTION OF EASTERN TX.

THE COMBINATION OF AIRMASS MODIFICATION WITHIN THE BOUNDARY LAYER
WITH THE LINGERING COLD POOLS AND WHAT APPEARS TO BE RIGHT EXIT
REGION FORCING (UPPER LEVEL CONVERGENCE) FROM THE SUBTROPICAL JET
STREAK PER THE LATEST WATER VAPOR LOOPS CONTINUES TO SHUT OFF NEW
CONVECTION ACROSS TX. THE CONCERN FOR THE OVERNIGHT PERIOD IS THAT
THE BEST UPPER LEVEL SUPPORT (UPPER DIVERGENCE ENHANCED FROM THE
RIGHT ENTRANCE REGION OF THE JET STREAK ACROSS THE MID MS VLY)
WILL SHIFT FARTHER EAST INTO THE LOWER-MID MS VALLEY...AS
SUPPORTED BY THE MOST RECENT HRRR AND RAP TRENDS WHICH FINALLY
APPEAR TO HAVE A HANDLE ON THE CONVECTIVE TRENDS.

HURLEY

PREVIOUS DISCUSSION BELOW...

AS THE HEIGHT FALLS FROM THE H5 TROF LIFT TOWARD THE MIDDLE MS
VALLEY/GREAT LAKES REGION...THE MID-LEVEL FLOW WILL REMAIN
SOUTHWESTERLY FROM THE SOUTHERN PLAINS UP INTO THE OH VALLEY.  A
SERIES OF IMPULSES TRACKING WITHIN THIS SOUTHWESTERLY FLOW WILL BE
THE IMPETUS FOR DEEP CONVECTION ACROSS THE SOUTHERN PLAINS/LOWER
AND MID MS VALLEY.  MODELS SHOW A BROAD WARM/MOIST SECTOR
EXTENDING ACROSS THE REGION WITH AMPLE INSTABILITY IN PLACE AS
MUCAPE VALUES PUNCH INTO THE 2000 TO 3000 J/KG RANGE. THE RECENT
00Z HIGH-RES GUIDANCE HAVE COME INTO BETTER AGREEMENT WITH THE
PLACEMENT OF THIS HEAVY RAINFALL.  IT APPEARS THE BEST CLUSTERING
IS FROM PARTS OF NORTHERN/CENTRAL TX UP INTO AR..WITH SEVERAL
INCHES OF RAIN BEING INDICATED THRU MONDAY MORNING.  GIVEN THE
DEEP-LAYERED MOISTURE AND AMPLE INSTABILITY IN PLACE...HOURLY
RAINFALL RATES MAY LOCALLY EXCEED FFG VALUES ACROSS THIS REGION.

TERRY
$$





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