SPC AC 271222
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0722 AM CDT SUN SEP 27 2009
VALID 271300Z - 281200Z
...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTERNOON AND TONIGHT
ACROSS MUCH OF THE GREAT LAKES REGION...MID MS VALLEY...AND OH
VALLEY...
MORNING SATELLITE LOOPS SHOW A POWERFUL MID/UPPER LEVEL SPEED MAX
NOSING INTO THE NORTHERN PLAINS. THIS FEATURE IS EXPECTED TO RESULT
IN SIGNIFICANT AMPLIFICATION OF A SHORTWAVE TROUGH OVER THE UPPER
MIDWEST AND GREAT LAKES REGION TONIGHT...PROVIDING STRONG LARGE
SCALE FORCING FOR ASCENT. SCATTERED SHOWERS AND THUNDERSTORMS WILL
AFFECT THIS REGION...WITH STRONG WINDS ALOFT AND MARGINAL
INSTABILITY POSING A RISK FOR A FEW SEVERE STORMS.
...WI/MI/ERN IA/IL LATE THIS AFTERNOON AND EVENING...
MODEL GUIDANCE IS IN FAIR AGREEMENT THAT A FAST-MOVING SURFACE COLD
FRONT WILL EXTEND FROM LAKE SUPERIOR INTO EASTERN IA BY EARLY
EVENING...AND SWEEP ACROSS THE GREAT LAKES...MID MS...AND OH VALLEYS
OVERNIGHT. SUBSTANTIAL HEATING WILL OCCUR AHEAD OF THE FRONT FROM
SOUTHERN WI INTO ERN MO/IL...WITH AFTERNOON TEMPERATURES WARMING
WELL INTO THE 70S AND MLCAPE VALUES OF 500-1000 J/KG. STRONG
CONVERGENCE ALONG THE FRONT WILL HELP TO INITIATE SCATTERED
THUNDERSTORMS...WHICH WILL TRACK EASTWARD ACROSS LAKE MICHIGAN AFTER
DARK. RAPID COOLING ALOFT AND STRENGTHENING WIND FIELDS SUGGEST
THAT A FEW OF THE STORMS MAY BECOME SEVERE WITH HAIL AND DAMAGING
WINDS POSSIBLE.
...LOWER MI/IND/OH OVERNIGHT...
AS THE SURFACE COLD FRONT SWEEPS EASTWARD OVERNIGHT...AN
INCREASINGLY MOIST BOUNDARY LAYER WILL PROMOTE GREATER THUNDERSTORM
COVERAGE. A FAST-MOVING LINE OF SHOWERS AND THUNDERSTORMS APPEARS
POSSIBLE FROM IND/LOWER MI EASTWARD ACROSS PARTS OF OH TONIGHT WITH
THE POTENTIAL FOR LOCALLY DAMAGING WINDS. WEAK INSTABILITY
PARAMETERS WILL BE THE MAIN MITIGATING FACTOR TO LESSEN THE RISK OF
A MORE WIDESPREAD WIND EVENT.
..HART/GRAMS.. 09/27/2009
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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