MESOSCALE DISCUSSION 0173
   NWS STORM PREDICTION CENTER NORMAN OK
   0627 PM CST TUE FEB 20 2007
   
   AREAS AFFECTED...SRN IL...SERN MO....NERN AR....WRN KY...WRN TN
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 26...
   
   VALID 210027Z - 210200Z
   
   SEVERE STORMS WITH HAIL WILL CONTINUE TO DEVELOP GENERALLY EWD
   ACROSS NRN/NWRN PORTIONS OF WATCH 26.
   
   SEVERE TSTMS CONTINUE TO INCREASE NEAR SURFACE WAVE AND FRONTAL ZONE
   FROM EXTREME NRN AR ACROSS THE MO BOOTHEEL REGION THIS EVENING.
   LARGE HAIL HAS BEEN REPORTED WITH ACTIVITY ACROSS SCOTT COUNTY MO
   OVER THE PAST HOUR. DEEP CONVECTION APPEARS TO BE DEVELOPING WITHIN
   AN AXIS OF STRONG LOW LEVEL CONVERGENCE ASSOCIATED WITH THE FRONTAL
   WAVE. AN INTENSE LEFT-MOVING STORM WAS TRACKING ENEWD TOWARD EXTREME
   SRN IL ATTM...AND ADDITIONAL CELLS WERE STRENGTHENING WWD AND SWWD
   ACROSS STODDARD...BUTLER...AND RIPLEY COUNTIES.
   
   AIR MASS IN THE VICINITY OF THESE STORMS SHOULD REMAIN  SUFFICIENTLY
   UNSTABLE TO MAINTAIN ROBUST UPDRAFTS WITHIN A STRONGLY SHEARED
   ENVIRONMENT. RECENT STORM TRENDS AND LATEST LITTLE ROCK SOUNDING
   INDICATED INTENSE UNIDIRECTIONAL EFFECTIVE SHEAR...ON THE ORDER OF
   50-70KT...WAS RESULTING IN SPLITTING SUPERCELLS. GREATEST THREAT
   WITH THIS ACTIVITY WILL CONTINUE TO BE LARGE HAIL FROM BOTH LEFT AND
   RIGHT MOVING UPDRAFTS GIVEN STEEP MID LEVEL LAPSE RATES AND MODERATE
   FORCING FOR ASCENT. IF RIGHT-MOVING CELLS CAN REMAIN DISCRETE WHILE
   DEVELOPING INTO LOW LEVEL MOIST AXIS ALIGNED WITH MS RIVER OVER NEXT
   HOUR OR SO...A BRIEF TORNADO CANNOT BE RULED OUT.
   
   ..CARBIN.. 02/21/2007
   
   
   ATTN...WFO...LMK...OHX...PAH...MEG...LZK...SGF...
   
   35508738 35439121 36779111 37288947 37288823 37008699