MESOSCALE DISCUSSION 0321
   NWS STORM PREDICTION CENTER NORMAN OK
   0518 PM CDT SAT MAR 28 2009
   
   AREAS AFFECTED...PORTIONS OF THE LOWER OH AND TN RIVER VALLEYS
   
   CONCERNING...TORNADO WATCH 91...
   
   VALID 282218Z - 282315Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 91 CONTINUES.
   
   SUPERCELLS CAPABLE OF PRODUCING TORNADOES...LARGE HAIL...AND DMGG
   WINDS WILL CONTINUE TO PROGRESS EWD AFFECT PORTIONS OF THE LOWER OH
   AND TN RIVER VALLEYS.
   
   21Z SURFACE ANALYSIS PLACES A 993 MB NEAR THE IL/IN/KY
   BORDERS...WITH A COLD FRONT EXTENDING SWD THROUGH MIDDLE TN AND A
   WARM FRONT EXTENDING EWD THEN SEWD THROUGH SERN KY AND INTO NC.
   DISCRETE SUPERCELLS HAVE DEVELOPED ALONG THE COLD FRONT IN AN
   ENVIRONMENT CHARACTERIZED BY MARGINAL TO MODERATE INSTABILITY OWING
   TO AMPLE INSOLATION...AND IMPRESSIVE DEEP LAYER SHEAR AOA 60 KTS AS
   SAMPLED BY VAD WIND PROFILER DATA INVOF ONGOING CONVECTION. STEEP
   MID LEVEL LAPSE RATES HAVE ADVECTED INTO THE AREA...AND THIS IN
   COMBINATION WITH STRONG SHEAR WILL PROMOTE LARGE HAIL GROWTH AND THE
   POTENTIAL FOR DMGG WINDS. BACKED SURFACE FLOW...ESPECIALLY CLOSER TO
   THE WARM FRONT...WILL BE FAVORABLE FOR TORNADIC DEVELOPMENT. STORMS
   SHOULD RAPIDLY WEAKEN TO THE N AS THEY CROSS THE OH RIVER INTO MORE
   STABLE/COOLER AIR.
   
   ..HURLBUT.. 03/28/2009
   
   
   ATTN...WFO...MRX...LMK...OHX...BMX...HUN...PAH...
   
   LAT...LON   34228625 34348726 35738767 37418804 38268771 37898635
               37078608 34678560 34428562 34228625