MESOSCALE DISCUSSION 2118
   NWS STORM PREDICTION CENTER NORMAN OK
   0751 PM CDT THU OCT 18 2007
   
   AREAS AFFECTED...LWR OH VLY AND MID-SOUTH
   
   CONCERNING...TORNADO WATCH 722...
   
   VALID 190051Z - 190215Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 722 CONTINUES.
   
   THE THREAT FOR TORNADOES...SOME POSSIBLY STRONG AND/OR LONG
   TRACKED...WILL CONTINUE TO INCREASE THROUGH LATE EVENING FROM SRN
   IND SWD INTO CNTRL/WRN KY...MIDDLE/WRN TN AND EXTREME NRN MS.  
   
   NUMEROUS SUPERCELLS...A FEW EXHIBITING SIGNIFICANT LOW-LEVEL
   ROTATION...CONTINUE FROM WEST OF KSDF SWWD TO JUST E OF THE MS RVR
   IN NWRN MS AT 0030Z.  DOWNSTREAM AIR MASS CONTINUES TO DESTABILIZE
   OWING TO INCREASING BOUNDARY LAYER MOISTURE WITH 00Z BNA SOUNDING
   EXHIBITING ABOUT 1700 J/KG OF MLCAPE.  VWPS AND SOUNDINGS SHOW
   TREMENDOUS LOW-LEVEL SHEAR AND 50+ KTS OF 0-6KM SHEAR...ALL
   INDICATIVE OF SUPERCELLS WITH THE THREAT FOR STRONG TORNADOES OVER A
   VERY LARGE REAL ESTATE CENTERED ON THE LWR OH VLY/MIDWEST INTO THE
   MID-SOUTH.
   
   THROUGH LATE EVENING...GREATEST POTENTIAL FOR TORNADOES WILL EXIST
   ACROSS MIDDLE/WRN TN NWD INTO IND WHERE MODELS FCST AN ACCELERATION
   OF THE SLY LLJ IN EXCESS OF 55 KTS BENEATH 95+ KTS OF MID-LEVEL SWLY
   FLOW.  EVENTUALLY...THE NUMBER OF STORMS MAY BEGIN TO MODULATE STORM
   MODE SOMEWHAT AS CELLS BEGIN TO MERGE.  BUT...SUCH STRONG AMBIENT
   SHEAR WILL MAINTAIN THE THREAT FOR EMBEDDED ROTATING STORMS WITH
   POSSIBLE TORNADOES AND HIGH WINDS.
   
   ..RACY.. 10/19/2007
   
   
   ATTN...WFO...LMK...OHX...IND...BMX...HUN...PAH...ILX...MEG...JAN...LSX...
   
   38448905 39018683 38778555 38218494 37198542 35278667
   33988727 32848787 33058874 33329001 33679075