DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 220729
SWODY3
SPC AC 220728

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0228 AM CDT MON OCT 22 2012

VALID 241200Z - 251200Z

...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/UPPER MS VALLEY ON THE PERIPHERY OF
A CLOSED/LEAD PORTION OF THE UPPER TROUGH OVER THE CENTRAL CANADIAN
PRAIRIES/FAR NORTHERN CONUS PLAINS. STEADY SURFACE CYCLOGENESIS IS
ANTICIPATED ESPECIALLY INTO WEDNESDAY NIGHT ACROSS THE UPPER MS
VALLEY...WITH A STRONG COLD FRONT BECOMING INCREASINGLY DEFINED IN A
NORTHEAST-SOUTHEAST ORIENTATION ACROSS THE UPPER MIDWEST/MIDDLE MO
VALLEY/CENTRAL PLAINS BY LATE IN THE PERIOD.

...MIDDLE MO VALLEY/UPPER MIDWEST/UPPER MS VALLEY...
CURRENT INDICATIONS ARE THAT RELATIVELY WEAK INHIBITION MAY EXIST
WITHIN A RELATIVELY MOIST /LOWER 60 F SURFACE DEWPOINTS/ AND
POTENTIALLY UNSTABLE /MLCAPE TO 1000-1500 J PER KG/ AIRMASS TO THE
EAST OF THE AFOREMENTIONED COLD FRONT/DEVELOPING SURFACE LOW.
HOWEVER...THE LIKELIHOOD/EXTENT OF SURFACE BASED CONVECTIVE
DEVELOPMENT THROUGH PEAK HEATING IS A BIT UNCERTAIN...ESPECIALLY
GIVEN INITIALLY MODEST BROAD SCALE FORCING FOR ASCENT AND THE
POSSIBILITY OF RESIDUAL CAPPING ALOFT VIA AN ELEVATED MIXED LAYER.
HOWEVER...ANY SURFACE BASED DEVELOPMENT THAT DOES DEVELOP/MATURE
THROUGH LATE AFTERNOON/EARLY EVENING COULD POSE A SEVERE RISK GIVEN
AMPLE VERTICAL SHEAR/INSTABILITY. WITH SUPERCELLS AT LEAST
CONDITIONALLY POSSIBLE...THIS COULD INCLUDE SEVERE HAIL/WIND AND
PERHAPS SOME TORNADO POTENTIAL ACROSS PORTIONS OF IA/SOUTHERN MN
INTO NORTHWEST WI.

OF GREATER LIKELIHOOD WILL BE FOR CONVECTION TO INCREASE WEDNESDAY
NIGHT NEAR MUCH OF THE EASTWARD-SHIFTING FRONTAL ZONE...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 AND PERHAPS
STRONG/SEVERE WIND GUSTS DURING THE EVENING.

A CATEGORICAL SLIGHT RISK MAY BE WARRANTED FOR PORTIONS OF THE
REGION IN SUBSEQUENT OUTLOOKS AS DETAILS BECOME BETTER REFINED.

..GUYER.. 10/22/2012

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