SWODY2
SPC AC 201723
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1223 PM CDT MON SEP 20 2010
VALID 211200Z - 221200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE MID MS VALLEY...
...MID MS VALLEY/GREAT LAKES...
NRN PLAINS SHORTWAVE TROUGH WILL EJECT QUICKLY INTO THE UPPER GREAT
LAKES REGION DURING THE DAY2 PERIOD WITH WEAK HEIGHT FALLS EXPECTED
AS FAR SOUTH AS PORTIONS OF IA INTO NRN IL. THIS FEATURE WILL FORCE
A COLD FRONT TO A POSITION FROM THE U.P. OF MI...SWWD INTO CNTRL IA
AT 18Z BEFORE TRAILING INTO THE HIGH PLAINS OF WRN KS. IN ALL
LIKELIHOOD CONVECTION INDUCED BY FRONTAL ASCENT WILL BE ONGOING AT
12Z ACROSS WI/IA...MUCH OF THIS BEHIND THE LEADING WIND SHIFT AIDED
IN PART BY A STRONG BUT VEERED LLJ.
HAVE OPTED TO INCREASE SEVERE PROBS ACROSS PARTS OF THE MID MS
VALLEY REGION FOR DIURNALLY ENHANCED CONVECTION ALONG/AHEAD OF COLD
FRONT. IT APPEARS STRONG HEATING WILL BE NOTED FROM LOWER MI...SWWD
INTO PORTIONS OF SERN IA/NRN MO. THIS WILL RESULT IN SUBSTANTIAL
SBCAPE BY MID AFTERNOON...1000-2000J/KG...ALONG SRN FRINGE OF
STRONGER FLOW ALOFT...SFC-6KM DEEP LAYER SHEAR ON THE ORDER OF
30-40KT SHOULD ALSO PROVE SUPPORTIVE OF ORGANIZED UPDRAFTS. LATEST
THINKING IS FRONTAL CONVECTION WILL BE NOTED ALONG THE ADVANCING
WIND SHIFT AS IT PROGRESSES ACROSS THE UPPER GREAT LAKES EXTENDING
INTO THE MID MS VALLEY. THIS ACTIVITY SHOULD GRADUALLY INCREASE IN
INTENSITY DURING THE AFTERNOON HOURS AS BOUNDARY LAYER WARMS AND LOW
LEVEL LAPSE RATES STEEPEN. GIVEN THE DEEP SWLY FLOW EXPECTED WITH
THIS ACTIVITY...THE PRIMARY SEVERE THREAT SHOULD BE STRONG WINDS AND
ISOLATED SEVERE HAIL. FRONTAL MCS SHOULD MIGRATE INTO THE NRN OH
VALLEY LATE IN THE PERIOD BUT SEVERE THREAT SHOULD GRADUALLY WANE
WITH LOSS OF DAYTIME HEATING.
..DARROW.. 09/20/2010
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