DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 230601
SWODY2
SPC AC 230600

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT TUE OCT 23 2012

VALID 241200Z - 251200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE UPPER MS
VALLEY/MIDDLE MO VALLEY...

...SYNOPSIS...
AN EASTWARD-SHIFTING LONGWAVE TROUGH WILL BE PREVALENT OVER THE
WESTERN HALF OF THE CONUS ON WEDNESDAY. STEADY HEIGHT FALLS ARE
EXPECTED OVER THE UPPER MIDWEST AND UPPER MS VALLEY ON THE PERIPHERY
OF A CLOSED/LEAD PORTION OF THE UPPER TROUGH OVER THE CENTRAL
CANADIAN PRAIRIES. STEADY SURFACE CYCLOGENESIS IS ANTICIPATED
ESPECIALLY INTO WEDNESDAY NIGHT ACROSS THE UPPER MS
VALLEY AND CENTRAL HIGH PLAINS...WITH A STRONG COLD FRONT BECOMING
INCREASINGLY DEFINED IN A NORTHEAST-SOUTHEAST ORIENTATION ACROSS THE
UPPER MIDWEST/UPPER MS VALLEY TO THE CENTRAL PLAINS BY WEDNESDAY
NIGHT.

...MIDDLE MO VALLEY/UPPER MIDWEST/UPPER MS VALLEY...
HEATING/DESTABILIZATION AND INCREASINGLY WEAK INHIBITION IS EXPECTED
NEAR/JUST AHEAD OF THE NORTHEAST-SOUTHWEST ORIENTED COLD FRONT AND
DEVELOPING SURFACE LOW WEDNESDAY AFTERNOON. BENEATH A RELATIVELY
STEEP PLUME OF MID LEVEL LAPSE RATES...LOWER 60S F SURFACE DEWPOINTS
MAY CONTRIBUTE TO AS MUCH AS 1500-2500 J/KG MLCAPE BY PEAK HEATING.
HOWEVER...THE LIKELIHOOD/EXTENT OF SURFACE BASED CONVECTIVE
DEVELOPMENT THROUGH PEAK HEATING REMAINS UNCERTAIN...ESPECIALLY
GIVEN INITIALLY MODEST BROAD SCALE FORCING FOR ASCENT AND THE
POSSIBILITY OF RESIDUAL CAPPING ALOFT VIA THE ELEVATED MIXED LAYER.
HOWEVER...ANY DEVELOPMENT THAT DOES OCCUR/MATURE THROUGH LATE
AFTERNOON/EARLY EVENING COULD POSE A SURFACE BASED SEVERE RISK GIVEN
AMPLE VERTICAL SHEAR/INSTABILITY...WITH SUPERCELLS AT LEAST
CONDITIONALLY POSSIBLE. THIS COULD INCLUDE SEVERE HAIL/WIND AND SOME
TORNADO POTENTIAL ACROSS PORTIONS OF IA/SOUTHERN MN INTO WESTERN WI.

A GREATER LIKELIHOOD WILL BE FOR CONVECTION TO INCREASE IN EARNEST
WEDNESDAY NIGHT NEAR MUCH OF THE EASTWARD-SHIFTING FRONTAL ZONE FROM
THE UPPER MS VALLEY TO THE CENTRAL PLAINS. THIS WILL BE AS FORCING
FOR ASCENT APPRECIABLY INCREASES LATE WEDNESDAY INTO THURSDAY WITH
AID OF LARGE SCALE HEIGHT FALLS AND A COUPLED UPPER JET. WITH
INCREASING FORCING FOR ASCENT/VERTICAL SHEAR...SUFFICIENT
MOISTURE/INSTABILITY ATTENDANT TO THE FRONTAL ZONE WILL ALLOW FOR
THE POSSIBILITY OF AT LEAST SPORADIC SEVERE HAIL. SOME STRONG/SEVERE
WIND GUSTS MAY ALSO BE POSSIBLE DURING THE EVENING...ALTHOUGH THE
UNDERCUTTING NATURE OF THE FRONT SHOULD TEMPER THIS POTENTIAL.

..GUYER.. 10/23/2012

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