DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 040551
SWODY2
SPC AC 040549

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1249 AM CDT TUE SEP 04 2012

VALID 051200Z - 061200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE UPPER
GREAT LAKES AND MIDWEST REGIONS...

...SYNOPSIS...
BROAD CYCLONIC FLOW FIELD ALOFT IS AGAIN PROGGED ACROSS THE NRN HALF
OF THE CONUS...S OF THE SLOW-MOVING CANADIAN PRAIRIE VORTEX.
MULTIPLE SHORT-WAVE FEATURES ARE PROGGED TO MOVE QUICKLY EWD ACROSS
THE NRN U.S. WITHIN THE FAST FLOW FIELD. AT THE SURFACE...A COLD
FRONT WILL CONTINUE ADVANCING EWD ACROSS THE MS VALLEY INTO THE
MIDWEST/OH VALLEY REGION. THIS FRONT WILL LIKELY BE THE FOCUS FOR
THE MAIN AREA OF SEVERE POTENTIAL THIS PERIOD.

...UPPER GREAT LAKES/MIDWEST...
SHOWERS AND SCATTERED THUNDERSTORMS SHOULD BE ONGOING AT THE START
OF THE PERIOD ACROSS PORTIONS OF THE UPPER MIDWEST/UPPER MS
VALLEY/WRN UPPER GREAT LAKES REGION...ALONG AND AHEAD OF THE
ADVANCING COLD FRONT. AS THE FRONT PROGRESSES EWD INTO A
DESTABILIZING WARM SECTOR...AN AFTERNOON INCREASE IN CONVECTION CAN
BE EXPECTED -- AIDED BY MODERATELY STRONG WNWLYS ALOFT SPREADING EWD
ATOP THE FRONTAL ZONE. WITH TIME...EVOLUTION OF AT LEAST A
SEMI-ORGANIZED LINE OF STORMS APPEARS LIKELY FROM WI SWD INTO
IL...WITH LOCALLY DAMAGING WINDS AND HAIL ACCOMPANYING BOTH THE LINE
AS WELL AS OTHER/MORE ISOLATED STORMS/STORM CLUSTERS.

SOME THREAT SHOULD CONTINUE INTO THE EVENING AS STORMS SPREAD ACROSS
WI AND IL AND INTO LOWER MI. EVENTUALLY HOWEVER...THE LOSS OF
DIURNAL HEATING/INSTABILITY WILL RESULT IN A SLOWLY DIMINISHING
SEVERE THREAT.

..GOSS.. 09/04/2012

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