SWODY2
SPC AC 231729
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1229 PM CDT WED MAY 23 2007
VALID 241200Z - 251200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE UPPER
MIDWEST...
..UPPER MIDWEST...
AN UPPER-LEVEL LOW OVER SRN CANADA WILL LIFT NWD TONIGHT AS A
SHORTWAVE TROUGH MOVES NEWD ACROSS THE UPPER MIDWEST THURSDAY. AT
THE SFC...A COLD FRONT WILL MOVE SEWD ACROSS THE UPPER MIDWEST AND
SHOULD BE POSITIONED FROM CNTRL WI EXTENDING SSWWD INTO ERN IA BY
LATE THURSDAY AFTERNOON. LARGE-SCALE ASCENT ASSOCIATED WITH THE
UPPER-LEVEL TROUGH AND LOW-LEVEL CONVERGENCE ALONG THE FRONT WILL BE
FAVORABLE FOR THE DEVELOPMENT OF NUMEROUS THUNDERSTORMS ALONG THE
COLD FRONT THURSDAY AFTERNOON AND EVENING.
MODEL FORECASTS MOVE AN 80 KT MID-LEVEL JET ASSOCIATED WITH THE
UPPER-LEVEL TROUGH QUICKLY NNEWD FROM THE CNTRL PLAINS INTO WI BY
LATE THURSDAY AFTERNOON. AS A RESULT...A BROAD ZONE OF STRONG
VERTICAL SHEAR PROFILES WILL EXIST ALONG THE FRONTAL BOUNDARY. THE
SHEAR SHOULD BE QUITE ADEQUATE FOR ORGANIZED THUNDERSTORMS.
HOWEVER...QUESTIONS REMAIN CONCERNING DESTABILIZATION. CLOUD COVER
FROM THE PREVIOUS NIGHTS CONVECTION COULD LIMIT INSTABILITY ACROSS
MUCH OF THE REGION. IN ADDITION...MID-LEVEL LAPSE RATES ON FORECAST
SOUNDINGS DO NOT APPEAR PARTICULARLY STEEP THURSDAY WHICH COULD BE
PROBLEMATIC. IF POCKETS OF MODERATE INSTABILITY CAN DEVELOP...THE
STRONG VERTICAL SHEAR COULD BE FAVORABLE FOR A FEW SUPERCELLS WITH
HAIL AND ISOLATED WIND DAMAGE POTENTIAL. IF A LINEAR MCS QUICKLY
ORGANIZES DURING THE LATE AFTERNOON...THEN THE PREFERRED STORM MODE
WOULD BE MULTICELL. IF A LINEAR MCS DEVELOPS...THE VERY STRONG
LOW-LEVEL FLOW AND UNIDIRECTIONAL LOW-LEVEL WIND PROFILES MAY RESULT
IN WIND DAMAGE AS THE PRIMARY THREAT. THE SEVERE THREAT SHOULD
DIMINISH DURING THE EVENING DUE TO THE WEAK INSTABILITY AND
DECREASING LIFT AS THE UPPER-LEVEL TROUGH AND MID-LEVEL JET MOVE
NNEWD AWAY FROM THE REGION.
..SRN AND CNTRL PLAINS....
ENERGY ASSOCIATED WITH AN UPPER-LEVEL TROUGH OVER THE CNTRL PLAINS
WILL MOVE NEWD AWAY FROM THE PLAINS REGION ON THURSDAY. AT THE
SFC...A COLD FRONT WILL MOVE SEWD ACROSS ERN KS...CNTRL OK AND WEST
TX. THIS BOUNDARY SHOULD BE THE FOCUS OF CONVECTIVE DEVELOPMENT
DURING THE LATE AFTERNOON AND EARLY EVENING HOURS THURSDAY.
ALTHOUGH...AREAS OF MODERATE INSTABILITY WILL LIKELY DEVELOP ALONG
AND AHEAD OF THE BOUNDARY THURSDAY AFTERNOON...FORECASTS SOUNDINGS
SHOW RELATIVELY WEAK VERTICAL SHEAR PROFILES WITH 0-6KM SHEAR OF 20
TO 30 KT. THIS SUGGESTS...THE THREAT FOR ORGANIZED STORM SHOULD
REMAIN LOCALIZED. IF VERTICAL SHEAR IS STRONGER THAN FORECAST ACROSS
PARTS OF THE WARM SECTOR...THEN A CONCENTRATED AREA OF SEVERE COULD
DEVELOP LATE THURSDAY AFTERNOON. AN UPGRADE TO SLIGHT RISK ACROSS
PARTS OF THE REGION MAY BE NECESSARY ONCE CERTAINTY INCREASES
CONCERNING THE LOCATION OF MAXIMUMS IN INSTABILITY THURSDAY
AFTERNOON. THE MAIN THREATS WOULD BE LARGE HAIL AND ISOLATED WIND
DAMAGE. ANY SEVERE THREAT THAT DEVELOPS WILL LIKELY REMAIN MARGINAL
AND CONCENTRATED NEAR PEAK HEATING.
.BROYLES.. 05/23/2007
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