SWODY1
SPC AC 211252
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0752 AM CDT TUE SEP 21 2010
VALID 211300Z - 221200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN PARTS OF THE CNTRL
PLNS INTO THE MID MS VLY AND LWR MI...
...SYNOPSIS...
FAST...LOW AMPLITUDE CYCLONIC FLOW WILL PREVAIL OVER THE NORTH
CNTRL STATES TODAY AS NW ONT UPR LOW CONTINUES NE TOWARD HUDSON BAY.
AT THE SAME TIME...SHORTWAVE IMPULSE TRAILING SW INTO THE CNTRL
PLNS WILL MOVE MORE SLOWLY E/NE ACROSS THE MID/UPR MS VLY THIS
AFTN...AND INTO LWR MI BY EVE. AT THE SFC...COLD FRONT ASSOCIATED
WITH THE ONT LOW EXPECTED TO PROGRESS STEADILY E/SE ACROSS WI AND
MI...AND MORE SLOWLY S/SE ACROSS THE MID MS VLY/CNTRL PLNS. THE
FRONT WILL BE THE MAIN FOCUS FOR DIURNALLY ENHANCED STORM
DEVELOPMENT THROUGH THE PERIOD.
...ERN PARTS OF THE CNTRL PLNS TO MID MS VLY/LWR MI...
WHILE THE MEAN FLOW WILL SLOWLY DIMINISH ACROSS THE UPR MIDWEST
TODAY...A BELT OF SEASONABLY STRONG /40+ KT/ UNIDIRECTIONAL LOW-MID
TROPOSPHERIC WSW FLOW WILL PERSIST...ESPECIALLY FROM NRN IL/SRN WI
ENE INTO LWR MI. COMBINATION OF SFC HEATING...CONTINUED LOW LVL
MOISTURE INFLOW...ASCENT WITH APPROACHING SHORTWAVE IMPULSE...AND
FRONTAL UPLIFT SHOULD BE SUFFICIENT TO SUPPORT SCTD STORM
DEVELOPMENT ACROSS REGION BY MID TO LATE AFTN AS CINH IS OVERCOME.
STRENGTH OF FLOW AND RELATIVELY STEEP LOW TO MID LVL LAPSE RATES
SUGGEST THAT CONVECTION WILL ORGANIZE INTO CLUSTERS AND BANDS...WITH
EMBEDDED BOWING SEGMENTS POSING A RISK FOR SWATHS OF DMGG WIND AND
PERHAPS HAIL THROUGH EARLY TONIGHT.
FARTHER SW ALONG THE COLD FRONT...SOMEWHAT GREATER LOW LVL MOISTURE
AVAILABILITY AND MORE FOCUSED LOW LVL CONVERGENCE MAY SUPPORT SCTD
STORM DEVELOPMENT OVER NRN MO...NRN KS AND PERHAPS SRN IA LATER
TODAY...DESPITE PASSAGE OF UPR IMPULSE. WITH SFC DEWPOINTS NEAR 70F
AND MLCAPE OF 2000-3000 J/KG...SETUP MAY PROVE FAVORABLE FOR A FEW
SUSTAINED STORMS AND EVEN A COUPLE SLOWLY MOVING SUPERCELLS WITH
LARGE HAIL/HIGH WIND AND PERHAPS A TORNADO.
INCREASING LOW LVL WAA/MOISTURE TRANSPORT ATOP STALLING FRONTAL ZONE
MAY SUPPORT DEVELOPMENT OF SCTD ELEVATED STORMS WITH HAIL OVER PARTS
OF NEB...WRN IA...AND POSSIBLY SRN SD TONIGHT AND EARLY WED.
..CORFIDI/SMITH.. 09/21/2010
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