MESOSCALE DISCUSSION 1050
   NWS STORM PREDICTION CENTER NORMAN OK
   0100 PM CDT THU JUN 11 2009
   
   AREAS AFFECTED...S-CNTRL IL
   
   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 
   
   VALID 111800Z - 111900Z
   
   A NON-ZERO BRIEF TORNADO THREAT MAY DEVELOP ACROSS PARTS OF S-CNTRL
   IL.  A WW IS UNLIKELY GIVEN ISOLD AND MARGINAL NATURE OF THREAT.
   
   SUBJECTIVE SURFACE ANALYSIS PLACES A 1006 MB LOW NEAR ALN WITH A
   WEAK LOW LEVEL CONVERGENCE ZONE EXTENDING FROM ALN GENERALLY EWD TO
   30 MI SSW MTO.  ALONG AND N OF THIS ZONE/BOUNDARY...BACKED SELY
   WINDS HAVE BEEN NOTED IN RECENT SURFACE OBS.  RADAR/SATELLITE MOSAIC
   SHOWS A MCV 45 MI NNW STL MOVING SE ACROSS SW AND S-CNTRL IL THE
   NEXT FEW HOURS.  AHEAD OF THIS FEATURE...A MOIST LOW LEVEL
   ENVIRONMENT HAS BECOME MODERATELY UNSTABLE /1500 J/KG MLCAPE/
   ACCORDING TO OBJECTIVE ANALYSIS AS TEMPS WARM TO NEAR 80 F ON NOSE
   OF STEEPER 0-2 KM LAPSE RATES.  DESPITE WEAK LOW LEVEL SHEAR IN AREA
   VWP DATA...BACKED LOW LEVEL WINDS ON THE IMMEDIATE COOL SIDE OF THE
   BOUNDARY WILL LOCALLY ENHANCE OTHERWISE MARGINAL LOW LEVEL SHEAR
   AMIDST A FAVORABLE LOW LCL ENVIRONMENT.  
   
   RECENT LSX RADAR IMAGERY /AROUND 1730Z/ DISPLAYED MODEST LOW LEVEL
   ROTATION WITH THE MACOUPIN/MONTGOMERY COUNTY STORM.  EXPECTING THIS
   TREND TO CONTINUE FOR STORMS THAT ARE SITUATED ALONG AND NEAR
   BOUNDARY FOR THE NEXT FEW HOURS POSING PERHAPS AN ISOLD WEAK TORNADO
   THREAT.
   
   ..SMITH.. 06/11/2009
   
   
   ATTN...WFO...ILX...LSX...
   
   LAT...LON   39279001 39418945 39388886 39178827 38908812 38618839
               38768923 38908995 39099014 39279001