SWOD48
SPC AC 200857
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0357 AM CDT TUE SEP 20 2011
VALID 231200Z - 281200Z
...DISCUSSION...
MEDIUM-RANGE MODELS AGREE THAT THE PRIMARY FEATURE TO PREVAIL ACROSS
THE U.S. AT MID LEVELS WILL BE A LARGE TROUGH/LOW INVOF THE UPPER
GREAT LAKES/UPPER MIDWEST. WITH TIME...THIS FEATURE IS PROGGED TO
BECOME COMPLETELY CUT OFF FROM THE MAIN BELT OF WLYS SHIFTING NWD
ACROSS CANADA. AS IT BECOMES CUT OFF...THE FEATURE IS PROGGED TO
LINGER IN PLACE -- OR EVEN RETROGRADE SLIGHTLY...AND THUS REMAIN
ACROSS THE UPPER MIDWEST REGION INTO DAY 7 AFTER WHICH IS BEGINS TO
BE PICKED UP BY THE WLYS AND SHIFTS EWD ACROSS THE OH VALLEY AND
INTO THE NORTHEAST THROUGH DAY 8.
DESPITE FAIR AGREEMENT BETWEEN THE GFS AND ECMWF IN TERMS OF THEIR
HANDLING OF THIS FEATURE THROUGH THE END OF THE
PERIOD...WIDESPREAD/SUBSTANTIAL SEVERE THREAT IS NOT EVIDENT. MINOR
EPISODES OF STRONG/POSSIBLY SEVERE STORMS WILL LIKELY OCCUR ON
SEVERAL DAYS AROUND THE PERIPHERY OF THE UPPER CYCLONIC
CIRCULATION...BUT DEGREE OF EXPECTED THREAT AND DIFFICULTY
HIGHLIGHTING ANY SPECIFIC AREA ON SPECIFIC DAYS PRECLUDES
INTRODUCTION OF ANY THREAT AREAS THIS PERIOD.
..GOSS.. 09/20/2011
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