SWOD48
SPC AC 170753
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0253 AM CDT MON SEP 17 2007
VALID 201200Z - 251200Z
..DISCUSSION...
LATEST MEDIUM RANGE GUIDANCE HAS COME INTO SLIGHTLY BETTER AGREEMENT
IN THE TIMING AND AMPLITUDE OF A SHORT WAVE TROUGH WHICH WILL
TRANSLATE EWD THROUGH THE CANADIAN PRAIRIES AND N-CNTRL STATES ON
THU/DAY 4 AND FRI/DAY 5. THESE DATA SUGGEST THAT THE POTENTIALLY
MOST ACTIVE SEVERE WEATHER PERIOD WILL EXIST ON DAY 4 ALONG WARM
FRONT OVER THE DAKOTAS INTO MN. HERE...A MOIST AND UNSTABLE AIR
MASS WILL BECOME COLOCATED WITH INCREASED FORCING FOR ASCENT AND
VERTICAL SHEAR WITH THE APPROACH OF SHORT WAVE TROUGH THROUGH THE
NRN HIGH PLAINS. THIS SEVERE THREAT MAY CONTINUE INTO DAY 5 OVER
THE UPPER MS VALLEY INTO UPPER GREAT LAKES...HOWEVER IT APPEARS THAT
THE BETTER FORCING FOR ASCENT AND INSTABILITY MAY TEND TO DEVELOP
NWD INTO ONTARIO.
THEREAFTER...DIFFERENCES EXIST IN THE TIMING AND EVOLUTION OF
CUT-OFF LOW OVER THE SWRN CONUS DURING THE LATTER PART OF THE
EXTENDED PERIOD. MOREOVER...QUESTIONS REGARDING THE CHARACTER OF
THE BOUNDARY LAYER AIR MASS OVER THE PLAINS STILL EXISTS.
THEREFORE...NO ADDITIONAL SEVERE WEATHER AREAS WILL BE DELINEATED.
.MEAD.. 09/17/2007
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