SWODY1
SPC AC 111223
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0723 AM CDT TUE MAY 11 2010
VALID 111300Z - 121200Z
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT FOR
OK/KS EWD TO NRN AR AND MO...
...SYNOPSIS...
AN INITIAL MIDLEVEL SHORTWAVE TROUGH OVER THE OH VALLEY WILL
CONTINUE TO DECAY AND MOVE EWD TO PA/NY AS LARGE SCALE HEIGHT RISES
OCCUR OVER THE MS VALLEY. UPSTREAM...A HIGH-AMPLITUDE TROUGH/CLOSED
LOW WILL PROGRESS EWD FROM THE GREAT BASIN TO THE CENTRAL ROCKIES.
THE APPROACH OF THE GREAT BASIN TROUGH WILL INDUCE LEE CYCLOGENESIS
ACROSS THE SRN HIGH PLAINS AND STRENGTHENING LOW-LEVEL SLY FLOW
FARTHER E ACROSS TX/OK/KS. THIS WILL ALLOW THE STALLED FRONT ALONG
I-44 IN OK TO MOVE NWD AS A WARM FRONT THIS AFTERNOON INTO TONIGHT.
...OH VALLEY TO SRN PLAINS THROUGH TONIGHT...
ASIDE FROM THE ELEVATED CONVECTION MOVING EWD OVER WRN OH...
THUNDERSTORM COVERAGE SHOULD REMAIN ISOLATED THIS AFTERNOON/EVENING
ALONG THE OH VALLEY PORTION OF THE FRONT. ASCENT WILL DIMINISH AS
THE MIDLEVEL WAVE MOVES BY EARLY IN THE DAY...LEAVING A NARROW
CORRIDOR OF MOISTENING/DESTABILIZATION ALONG THE STALLING FRONT THIS
AFTERNOON. STORMS THAT FORM ALONG THE FRONT COULD DEVELOP SUPERCELL
STRUCTURES GIVEN 0-6 KM BULK SHEAR NEAR 50 KT...BUT WEAK INSTABILITY
WITH NEWD EXTENT FROM THE LOWER OH VALLEY WILL LIMIT THE OVERALL
HAIL/WIND THREAT.
STRONGER SURFACE-BASED INSTABILITY IS EXPECTED ALONG AND S OF THE
FRONT FROM SRN MO/AR INTO CENTRAL/SRN OK...WITH MLCAPE OF 3000-4000
J/KG EXPECTED ACROSS OK WHERE NEAR 70 F BOUNDARY LAYER DEWPOINTS LIE
BENEATH 7-8 C/KM MIDLEVEL LAPSE RATES. THUNDERSTORM COVERAGE ACROSS
OK/AR/MO DURING THE AFTERNOON IS IN QUESTION GIVEN MINIMAL LARGE
SCALE SUPPORT FOR ASCENT AND A RATHER STRONG CAP. IF STORMS DO FORM
ALONG THE FRONT AND/OR DRYLINE THIS AFTERNOON...THE ENVIRONMENT WILL
BE FAVORABLE FOR SUPERCELLS WITH A MORE SUBSTANTIAL HAIL/TORNADO
THREAT THAN INDICATED BY THE UNCONDITIONAL PROBABILITIES. THE MORE
PROBABLE SCENARIO IS FOR ELEVATED CONVECTION TO FORM TONIGHT AS THE
LLJ AND WAA STRENGTHEN FROM NRN OK INTO KS/MO...WHERE ELEVATED
INSTABILITY AND EFFECTIVE BULK SHEAR WILL BE SUFFICIENT FOR
ORGANIZED CLUSTERS/SUPERCELLS WITH VERY LARGE HAIL...AND ISOLATED
DAMAGING WIND.
..THOMPSON/HURLBUT.. 05/11/2010
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