MESOSCALE DISCUSSION 0124
   NWS STORM PREDICTION CENTER NORMAN OK
   0133 PM CST WED FEB 18 2009
   
   AREAS AFFECTED...CNTRL/ERN KY INTO MIDDLE/ERN TN
   
   CONCERNING...TORNADO WATCH 23...
   
   VALID 181933Z - 182100Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 23 CONTINUES.
   
   PRIMARY SEVERE THREAT /I.E. LARGE HAIL...DAMAGING WINDS AND PERHAPS
   A TORNADO OR TWO/ IS EXPECTED TO CONTINUE ACROSS ERN HALF OF WW AREA
   THROUGH 21Z.  BASED ON EXTRAPOLATION OF CURRENT STORM MOTIONS...ERN
   EXTENSION OF THIS THREAT MAY DEVELOP E OF WW AREA BY 2000-2030Z AND
   AN ADDITIONAL WW MAY BE REQUIRED.
   
   AS OF 1920Z...REGIONAL RADAR IMAGERY INDICATED A BAND OF SCATTERED
   STRONG TO SEVERE TSTMS FROM KNOX COUNTY KY WSWWD TO WAYNE COUNTY KY
   AND THEN MORE SWD THROUGH MIDDLE TN.  THE MOST INTENSE STORM /A
   SUPERCELL/ WAS LOCATED AT THE INTERSECTION OF WHITE...PUTNAM AND
   CUMBERLAND COUNTIES TN WITH AN ESTIMATED STORM MOTION OF 265/45 KT.
   
   18Z BNA SOUNDING INDICATED THAT CONSIDERABLE WARMING IN THE BOUNDARY
   LAYER HAD DESTABILIZED AIR MASS DESPITE THE MARGINAL MOISTURE
   CONTENT WITH MLCAPE OF A FEW HUNDRED J/KG.  THIS SAME
   DESTABILIZATION PROCESS IS NOW OCCURRING FURTHER E OVER THE
   CUMBERLAND PLATEAU WHERE NOTABLE INCREASES IN BOUNDARY LAYER HEAT
   AND MOISTURE ARE OCCURRING PER 3-HR CHANGE FIELDS.  VERTICAL SHEAR
   REMAINS QUITE STRONG AND SUPPORTIVE OF ORGANIZED STORMS INCLUDING
   SUPERCELLS ASSUMING SUFFICIENT INSTABILITY DEVELOPS TO MAINTAIN
   ONGOING STORMS.  WHILE LARGE HAIL AND DAMAGING WIND GUSTS WILL BE
   THE PRIMARY SEVERE THREATS...AN ISOLATED TORNADO REMAINS POSSIBLE
   WITH THE MORE INTENSE SUPERCELLS.
   
   ..MEAD.. 02/18/2009
   
   
   ATTN...WFO...RLX...MRX...JKL...LMK...OHX...HUN...
   
   LAT...LON   35108687 36458559 37078417 37278297 37178251 36478255
               35568377 35118487 35038520 35108687