MESOSCALE DISCUSSION 1873
   NWS STORM PREDICTION CENTER NORMAN OK
   0340 PM CDT TUE SEP 21 2010
   
   AREAS AFFECTED...EASTERN IA/EXTREME NORTHEAST MO AND NORTHERN IL/FAR
   SOUTHERN WI
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 677...
   
   VALID 212040Z - 212215Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 677
   CONTINUES.
   
   SEVERE TSTM WATCH 677 CONTINUES UNTIL 02Z...WITH DAMAGING
   WINDS/BOUTS OF SEVERE HAIL AS THE PRIMARY HAZARDS...ESPECIALLY
   ACROSS NORTHERN IL/FAR SOUTHERN WI.
   
   AMID A STEEP LAPSE RATE/STRONGLY SHEARED ENVIRONMENT AHEAD OF A COLD
   FRONT...SURFACE COLD POOL EXPANSION APPEARS PROBABLE OVER THE NEXT
   FEW HOURS INTO NORTHERN IL/FAR SOUTHERN WI...WITH ADDITIONAL FORWARD
   PROPAGATION/ACCELERATION LIKELY WITH AN ONGOING QUASI-LINEAR
   STRONG/SEVERE TSTM CLUSTER NEAR THE MS RIVER. A QUASI-LINEAR MODE
   WITH EMBEDDED BOWS WILL REMAIN DOMINANT...AS REGIONAL
   PROFILERS/WSR-88D VWP DATA ARE INDICATIVE OF STRONG/LARGELY
   UNIDIRECTIONAL WIND PROFILES...WITH AROUND 35-40 KT OF EFFECTIVE
   SHEAR. AS SUCH...ASIDE FROM BOUTS OF SEVERE HAIL...DAMAGING WINDS
   WILL BE AN APPRECIABLE CONCERN THE REMAINDER OF THE
   AFTERNOON...ESPECIALLY ACROSS NORTHERN IL /EVENTUALLY INCLUDING THE
   CHICAGOLAND AREA/ AND FAR SOUTHERN WI.
   
   ..GUYER.. 09/21/2010
   
   
   ATTN...WFO...LOT...ILX...MKX...DVN...
   
   LAT...LON   41049205 41819051 42738973 43038855 42738760 41788722
               41098742 40618880 40389040 40389211 41049205