SPC AC 041246
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0746 AM CDT FRI SEP 04 2009
VALID 041300Z - 051200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
THE LARGE SCALE REGIME OF A WEAK MID LEVEL TROUGH FROM THE OH VALLEY
TO THE CENTRAL/SRN PLAINS...AN UPSTREAM RIDGE OVER THE ROCKIES...AND
A TROUGH JUST OFF THE PAC NW COAST...WILL PERSIST INTO TOMORROW.
THE PRIMARY THREAT AREAS FOR DEEP CONVECTION TODAY INTO TONIGHT WILL
BE ACROSS FL TO THE E OF A WEAK MID LEVEL TROUGH OVER THE ERN GULF
OF MEXICO...ACROSS THE SRN ROCKIES WITHIN A RESIDUAL LOW-MID LEVEL
MOISTURE PLUME...AND ACROSS THE SRN PLAINS.
...SRN PLAINS AREA TODAY...
AN EMBEDDED MID LEVEL VORTICITY CENTER OVER ERN KS...WITH AN
ASSOCIATED SURFACE FRONTAL SEGMENT...WILL ROTATE SSEWD TODAY AROUND
THE WRN PERIPHERY OF THE LARGER SCALE TROUGH OVER THE MID MS/OH
VALLEY REGION. THUNDERSTORM CLUSTERS ARE ONGOING OVER ERN KS IN
ASSOCIATION WITH THE SURFACE FRONT AND MID LEVEL WAVE...AND SOME
FORM OF THIS CONVECTION WILL LIKELY PERSIST AND DRIFT SWD/SEWD
THROUGH THE DAY. REGIONAL 12Z SOUNDINGS REVEAL THAT THE ONGOING
CONVECTION IS BEING SUPPORTED BY MUCAPE OF 1500-2000 J/KG BASED NEAR
850 MB...WHILE SURFACE-BASED INSTABILITY WILL INCREASE WITH SURFACE
HEATING ALONG THE SRN/SWRN FLANKS OF THE ONGOING STORMS FROM SRN KS
INTO NRN OK. MEANWHILE...DEEP LAYER VERTICAL SHEAR WILL BE
SUFFICIENT FOR ORGANIZED MULTICELL CLUSTERS...AND MARGINAL/BRIEF
SUPERCELL STRUCTURES...WITH THE POTENTIAL FOR ISOLATED DAMAGING
WINDS AND/OR LARGE HAIL. THE OVERALL COMBINATION OF INSTABILITY AND
VERTICAL SHEAR APPEARS MARGINAL FOR ANYTHING MORE THAN LOW HAIL AND
WIND PROBABILITIES.
FARTHER S IN TX...AN INITIAL FRONTAL SURGE HAS BEEN REINFORCED BY
OUTFLOW FROM OVERNIGHT CONVECTION. THE EFFECTIVE FRONTAL ZONE NOW
EXTENDS FROM W CENTRAL INTO CENTRAL TX...AND THIS RESIDUAL BOUNDARY
COULD SERVE TO FOCUS ADDITIONAL STRONG THUNDERSTORM DEVELOPMENT
TODAY. ISOLATED DOWNBURST WINDS AND/OR MARGINALLY SEVERE HAIL COULD
OCCUR THIS AFTERNOON...BUT THE POTENTIAL FOR ORGANIZED SEVERE STORMS
WILL BE LIMITED BY WEAK VERTICAL SHEAR TO THE S OF THE STRONGER BELT
OF MID-UPPER FLOW OVER KS/OK.
..THOMPSON/GARNER.. 09/04/2009
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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