SPC AC 160736
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0236 AM CDT TUE OCT 16 2007
VALID 181200Z - 191200Z
...THERE IS A MDT RISK OF SVR TSTMS ACROSS MUCH OF IL AND
INDIANA...SERN WI...SRN LOWER MI...AND PARTS OF WRN KY....
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS A LARGE PORTION OF THE
CONUS BETWEEN THE MS VALLEY AND THE APPALACHIANS...
...SYNOPSIS...
MID-LEVEL TROUGH CROSSING THE CENTRAL U.S. IS FORECAST TO INTENSIFY
AND TAKE ON AN INCREASINGLY-NEGATIVE TILT WITH TIME.
MEANWHILE...ASSOCIATED SURFACE LOW WILL MOVE FROM IA INTO THE UPPER
GREAT LAKES REGION THROUGH THE PERIOD AS COLD FRONT SWEEPS EWD
ACROSS THE MIDWEST/OH VALLEY AND SEWD ACROSS THE GULF COAST STATES
THROUGH 19/12Z.
...ERN CONUS ROUGHLY FROM THE MS VALLEY EWD TO THE APPALACHIANS...
WIDESPREAD/POTENTIALLY-SIGNIFICANT SEVERE WEATHER EVENT IS EVIDENT
FOR DAY 3...AS LARGE UPPER TROUGH/LOW AND ASSOCIATED STRONG COLD
FRONT MOVE EWD ACROSS THE MS VALLEY. AHEAD OF THE FRONT...A VERY
LARGE WARM SECTOR IS ANTICIPATED...WHICH COMBINED WITH SOME DIURNAL
HEATING SHOULD RESULT IN MARGINAL TO LOCALLY-MODERATE INSTABILITY.
ATOP THE MOIST/DESTABILIZING BOUNDARY LAYER...VERY STRONG DEEP
TROPOSPHERIC WIND FIELD IS FORECAST TO OVERSPREAD THE FRONTAL ZONE
INTO THE WARM SECTOR...WITH 60 TO 80 SSWLY FLOW AT MID-LEVELS
FORECAST ATOP THE FRONT DURING THE AFTERNOON.
SCATTERED STORMS/STORM CLUSTERS SHOULD BE ONGOING ACROSS A LARGE
PORTION OF THE AREA DURING THE DAY...WITH AN INCREASE IN CONVECTIVE
INITIATION EXPECTED IN MULTIPLE BANDS CLUSTERS ALONG/AHEAD OF COLD
FRONT AS IT CROSSES THE MS VALLEY DURING THE AFTERNOON. WHILE FLOW
ROUGHLY PARALLEL TO THE FRONT DOES NOT APPEAR TO FAVOR
NUMEROUS/PRIMARILY DISCRETE STORMS...STORM MODE IS IMPOSSIBLE TO
DETERMINE AT THIS POINT. IT WOULD APPEAR THAT SOME COMBINATION OF
ISOLATED AND LINEAR STORMS WILL BE ONGOING DURING THE AFTERNOON --
LIKELY PRODUCING HAIL/DAMAGING WINDS...AS SHEAR WILL BE
STRONGLY-SUPPORTIVE OF LONG-LIVED/WELL-ORGANIZED STORMS. DEGREE OF
LOW-LEVEL SHEAR AND PRESENCE OF MOIST BOUNDARY LAYER ALSO SUPPORTS A
THREAT FOR TORNADOES.
ATTM...WILL INTRODUCE A MODERATE RISK ACROSS PARTS OF THE
MIDWEST...WHICH MAY BE EXPANDED TO INCLUDE AREAS AS FAR S AS THE
GULF COAST STATES IN LATER FORECASTS.
THREAT WILL LIKELY CONTINUE INTO THE OVERNIGHT HOURS...PERHAPS
SHIFTING ACROSS THE APPALACHIANS LATE.
..GOSS.. 10/16/2007
CLICK TO GET WUUS03 PTSDY3 PRODUCT
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 1100Z
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