MESOSCALE DISCUSSION 2110
   NWS STORM PREDICTION CENTER NORMAN OK
   1136 AM CDT THU OCT 18 2007
   
   AREAS AFFECTED...SRN AND ERN WI...NRN IL
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 181636Z - 181900Z
   
   A FEW SEVERE THUNDERSTORMS ARE EXPECTED BY LATE AFTERNOON...WITH
   HAIL AND ISOLATED TORNADOES POSSIBLE. A WW MAY BE REQUIRED BY MID
   AFTERNOON.
   
   MODIFIED FORECAST SOUNDINGS AND CHARACTER OF THE CU FIELD INDICATE
   THE AIR MASS IS CURRENTLY CAPPED. HOWEVER...VISIBLE SATELLITE
   IMAGERY SHOWS AREAS OF HEATING OVER CNTRL AND ERN WI AS WELL AS OVER
   MUCH OF IL. MEANWHILE...RAPID COOLING IS TAKING PLACE ALOFT WITH
   STRONG UPPER VORTICITY LOBE SHIFTING NWD OUT OF IA/NRN IL INTO WI.
   CONTINUED HEATING AND UPPER COOLING WILL ERODE CAP BY LATE
   AFTERNOON...AND AT LEAST ISOLATED SEVERE STORMS ARE EXPECTED TO FORM
   WITHIN LOW LEVEL THETA-E AXIS FROM NRN IL INTO SRN/ERN WI.
   
   THE VERY STRONG DEEP LAYER SHEAR COMBINED WITH MARGINAL INSTABILITY
   SUGGEST HIGHLY SHEARED AND TILTED UPDRAFTS. HAIL WILL BE LIKELY WITH
   ANY STORM. OVERALL...HODOGRAPHS ARE FORECAST TO BE RELATIVELY
   STRAIGHT...BUT ANY LOCAL LOW LEVEL BACKING OF THE WINDS SUCH AS
   ALONG LAKE SHORE BOUNDARIES MAY ENHANCE TORNADO POTENTIAL.
   
   ..JEWELL.. 10/18/2007
   
   
   ATTN...WFO...MQT...GRB...LOT...MKX...DVN...DLH...ARX...
   
   42029004 43278979 43879008 44909055 45518997 45408847
   45198738 44908727 43198759 42448761 41868822