SWODY1
SPC AC 071245
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0745 AM CDT SAT MAY 07 2011
VALID 071300Z - 081200Z
...NO SVR TSTM AREAS FORECAST...
...OZARK PLATEAU INTO THE OH VALLEY...
MIDLEVEL VORTICITY MAXIMUM AND ATTENDANT 50-60 KT WNWLY JET STREAK
OVER THE MID/LOWER MO VALLEY WILL PROGRESS EWD INTO IL/IND BY
AFTERNOON BEFORE GRADUALLY WEAKENING ACROSS THE UPPER OH VALLEY LATE
TONIGHT. ASSOCIATED SURFACE LOW ANALYZED OVER S-CNTRL IA AS OF 12Z
WILL CONCURRENTLY DEVELOP EWD TO CNTRL IL BY MID AFTERNOON WITH
TRAILING BOUNDARY EXTENDING SWWD TO SECONDARY...THERMAL LOW FORMING
OVER NWRN TX.
ELEVATED CLUSTERS OF TSTMS ONGOING FROM CNTRL MO INTO N-CNTRL AR AND
EWD INTO SRN IL ARE EXPECTED TO GRADUALLY DECREASE IN AREAL COVERAGE
THIS MORNING IN CONJUNCTION WITH THE DIURNAL WEAKENING OF A
NOCTURNAL LLJ. IN THE WAKE OF THIS INITIAL TSTM ACTIVITY... MORNING
VISIBLE SATELLITE IMAGERY SUGGESTS THAT BREAKS IN THE CLOUDS SHOULD
ALLOW STRONGER DAYTIME HEATING TO OCCUR FROM NRN MO INTO CNTRL IL
AND PERHAPS WRN IND. WHEN COUPLED WITH BOUNDARY LAYER DEWPOINTS IN
THE 50S...EXPECT AFTERNOON AIR MASS TO BECOME AT LEAST MARGINALLY
UNSTABLE FROM VICINITY OF SURFACE LOW SWWD ALONG COLD FRONT WHERE
MLCAPE VALUES COULD APPROACH 500-1000 J/KG.
FORCING FOR ASCENT ASSOCIATED WITH ABOVE-MENTIONED VORTICITY MAXIMUM
IN CONCERT WITH LOW-LEVEL CONVERGENCE NEAR SURFACE LOW ARE EXPECTED
TO FOSTER ISOLATED TO WIDELY SCATTERED TSTMS THIS AFTERNOON OVER
CNTRL OR ERN IL. ACTIVITY WILL MOVE/DEVELOP SEWD INTO WRN PARTS OF
IND BEFORE WEAKENING THIS EVENING WITH THE LOSS OF DAYTIME HEATING.
GIVEN VERTICALLY VEERING WIND PROFILES WITH 50-60 KT OF DEEP NWLY
SHEAR -- PER 12Z OBSERVED AND MODEL FORECAST SOUNDINGS...THE
POTENTIAL WILL EXIST FOR ORGANIZED/ROTATING UPDRAFTS CAPABLE OF AT
LEAST SOME HAIL AND LOCALLY STRONG WIND GUSTS.
THE OVERALL SEVERE WEATHER THREAT WILL BE MODULATED BY THE DEGREE OF
SURFACE-BASED INSTABILITY THAT CAN DEVELOP BY AFTERNOON. SHOULD
SUBSEQUENT OBSERVATIONAL AND/OR MODEL DATA INDICATE GREATER
DESTABILIZATION THAN IS CURRENTLY FORECAST...AN UPGRADE TO A
CATEGORICAL SLIGHT RISK MAY BE REQUIRED AT 1630Z.
...SRN PLAINS...
STRONG DIABATIC HEATING...INCREASING BOUNDARY LAYER MOISTURE AND
STEEP MIDLEVEL LAPSE RATES WILL CONTRIBUTE TO A MODERATELY TO
STRONGLY UNSTABLE AIR MASS LATER TODAY E OF THE DRYLINE AND S OF
STATIONARY FRONT FROM PORTIONS OF OK/AR INTO TX. RISING MIDLEVEL
HEIGHTS AND A RESULTANT STRENGTHENING OF CAPPING INVERSION OBSERVED
ON 12Z REGIONAL SOUNDINGS WILL LIKELY INHIBIT STORM FORMATION
THROUGH THE DIURNAL HEATING CYCLE.
..MEAD/PETERS.. 05/07/2011
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