MESOSCALE DISCUSSION 0485
   NWS STORM PREDICTION CENTER NORMAN OK
   1156 PM CDT TUE APR 19 2011
   
   AREAS AFFECTED...SWRN/CNTRL OH...SERN IND...WRN KY...WRN TN...NRN MS
   
   CONCERNING...TORNADO WATCH 159...160...
   
   VALID 200456Z - 200630Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 159...160...CONTINUES.
   
   A NEW WW MAY BE NEEDED EAST OF THE ONGOING CONVECTION ACROSS
   PORTIONS OF SRN OH...WRN WV...ERN KY...CNTRL/ERN TN...AND NRN AL.
   
   AN EXTENSIVE QLCS STRETCHING FROM WRN OH AND SERN IND SWD INTO NRN
   MS CONTINUES PROGRESSING EWD. WELL-DEFINED BOWING LINE SEGMENTS OVER
   WRN KY AND FAR WRN TN WILL CONTINUE TO RAPIDLY MOVE EWD AT 50 KT.
   CONTINUED FORWARD PROPAGATION IS ANTICIPATED...BRING THE SEVERE
   THREAT INTO PORTIONS OF CNTRL KY AND ACROSS WRN TN/NRN MS DURING THE
   NEXT FEW HOURS...AS DEEP-LAYER SHEAR VECTORS CONTINUE TO MAINTAIN A
   COMPONENT ORTHOGONAL TO THE LEADING CONVECTIVE LINE. WIDESPREAD DMGG
   WINDS WILL REMAIN A CONCERN...ESPECIALLY WITH THE BETTER-DEFINED
   BOWING LINE SEGMENTS. FARTHER NORTH INTO SWRN AND CNTRL
   OH...CONVECTIVE OUTFLOW IS BEGINNING TO ACCELERATE AHEAD OF THE
   DEEPER CONVECTION...SUGGESTING THAT ASCENT WILL BECOME INCREASINGLY
   SLOPED /AS OPPOSED TO UPRIGHT/ WITH TIME AS THE LINE APPROACHES
   CNTRL AND S-CNTRL OH. HOWEVER...IN THESE AREAS...MODERATE
   INSTABILITY WITHIN THE WARM SECTOR SHOULD COMPENSATE...YIELDING A
   CONTINUED DMGG WIND POTENTIAL /ALBEIT NOT AS HIGH AS FARTHER SOUTH/.
   GIVEN THE OVERALL CONVECTIVE MODE BEING LINEAR...THE PRIMARY SEVERE
   THREAT WILL CONTINUE TO EVOLVE TOWARD DMGG WINDS. HOWEVER...A THREAT
   FOR ISOLATED TORNADOES PERSISTS GIVEN EFFECTIVE SRH VALUES AOA 300
   M2/S2 DUE TO A STRONG LOW-LEVEL JET. THIS IS ESPECIALLY THE CASE
   INTO NRN MS...WHERE CONVECTION REMAINS SOMEWHAT MORE DISCRETE.
   
   WHILE INSTABILITY EAST OF WW159 AND WW160 IS SOMEWHAT LESS THAN
   UPSTREAM...THE WELL-DEFINED COLD POOL CIRCULATIONS AND STRONG
   DEEP-LAYER WIND SHEAR COULD CONTINUE TO MAINTAIN A THREAT FOR DMGG
   WINDS. THUS...A NEW WATCH MAY BE NEEDED DOWNSTREAM OF THE ONGOING
   CONVECTION NEAR OR JUST AFTER 06Z.
   
   ..COHEN.. 04/20/2011
   
   
   ATTN...WFO...RLX...MRX...JKL...ILN...LMK...OHX...IND...BMX...
   HUN...PAH...MEG...JAN...
   
   LAT...LON   33979094 35068969 36558863 37128728 37758621 39388520
               40228354 39908239 38188239 36048451 34438651 33578822
               33429025 33979094