MESOSCALE DISCUSSION 0442
   NWS STORM PREDICTION CENTER NORMAN OK
   0557 PM CDT FRI APR 15 2011
   
   AREAS AFFECTED...IL/SERN MO/WRN AND MIDDLE TN/NRN MS/NWRN AL/WRN
   KY/SWRN INDIANA
   
   CONCERNING...TORNADO WATCH 142...143...
   
   VALID 152257Z - 160100Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 142...143...CONTINUES.
   
   SEVERE/ISOLATED TORNADO THREAT CONTINUES ACROSS VALID PORTIONS OF WW
   142/143.  THREAT SHIFTING EWD WITH TIME COULD REQUIRE NEW WW INTO
   PARTS OF ERN IL/SWRN INDIANA/MORE OF WRN KY.
   
   LATEST RADAR IMAGERY SHOWS A COMPLEX LINE OF STORMS ORGANIZING JUST
   E OF THE MS RIVER INTO WRN IL...WITH LEWPS/BOWS AND SOME EMBEDDED
   ROTATING UPDRAFTS.  A FEW CELLS JUST AHEAD OF THE LINE ARE ALSO
   DEVELOPING/ACQUIRING ROTATION BEFORE MERGING WITH THE ORGANIZING
   LINE.  
   
   THE MAIN AXIS OF INSTABILITY IS CONTAINED WITHIN THE TWO EXISTING
   WATCHES...WITH A TIGHT INSTABILITY GRADIENT ALONG THE NRN PORTION OF
   WW 142...LIMITING SEVERE POTENTIAL NORTH OF THIS WATCH.
   
   HOWEVER...WEAK -- BUT MARGINALLY-SUFFICIENT -- INSTABILITY EXTENDS
   JUST EAST OF THE EXISTING WATCHES -- ACROSS ERN IL AND FAR WRN KY
   TOWARD SWRN INDIANA/CENTRAL KY.  GIVEN FAVORABLE WIND SHEAR IN
   PLACE...A NEW/NARROW WATCH COULD BE REQUIRED TO EXTEND E OF WW 142.
   
   ..GOSS.. 04/15/2011
   
   
   ATTN...WFO...LMK...OHX...IND...BMX...HUN...PAH...LOT...ILX...
   MEG...JAN...LSX...DVN...
   
   LAT...LON   33849028 36109020 38049026 39869083 40529117 40869045
               40458838 39128634 37458596 35808700 33728750 33849028