MESOSCALE DISCUSSION 0521
   NWS STORM PREDICTION CENTER NORMAN OK
   1114 AM CDT THU APR 18 2013
   
   AREAS AFFECTED...PORTIONS LOWER MI...WRN OH...INDIANA EXCEPT NWRN
   PORTIONS...SRN IL...SERN MO.
   
   CONCERNING...TORNADO WATCH 122...123...124...
   
   VALID 181614Z - 181815Z
   
   CORRECTED FOR GEOGRAPHIC HEADER
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH
   122...123...124...CONTINUES.
   
   SUMMARY...REMAINDER WW 122 HAS BEEN EXTENDED UNTIL 18Z WITH ADDITION
   OF REYNOLDS COUNTY MO...PER COORD W/LSX WFO.  WWS 123-124 MAY BE
   CLEARED BEHIND PRIMARY CONVECTIVE BAND...WITH POSSIBLE EXCEPTION OF
   SRN PORTIONS WW 124 AHEAD OF CONVECTION MOVING NEWD FROM WW 122. 
   PORTIONS OH E OF WW 123 ARE BEING MONITORED FOR POSSIBLE WW BASED ON
   CONVECTIVE/DESTABILIZATION TRENDS.
   
   DISCUSSION...BAND OF TSTMS FROM LM SHORE OF LOWER MI SSWWD ACROSS
   NWRN INDIANA TO SERN MO -- WELL AHEAD OF SYNOPTIC SFC COLD FRONT AND
   LOW -- WILL CONTINUE MOVING ACROSS REMAINDER WW AREAS.  NET EWD
   MOTION HAS BEEN ABOUT 25 KT...WITH CONSIDERABLE LOCAL
   VARIABILITY...AND NEWD 40-50 KT SPEEDS ON EMBEDDED CONVECTIVE
   ELEMENTS.  MAIN THREAT WILL CONTINUE TO BE DAMAGING WIND...WITH OCNL
   TORNADOES POSSIBLE IN EITHER QLCS CIRCULATIONS OR EMBEDDED/BOW-ECHO
   MESOVORTICES.  
   
   BOTH VERTICAL SHEAR AND LOW-LEVEL MOISTURE WEAKEN WITH EWD EXTENT
   ATTM.  HOWEVER...COMBINATION OF MOIST/WARM ADVECTION AND DIABATIC
   SFC HEATING E OF CONVECTION WILL YIELD FAVORABLE BUOYANCY -- I.E.
   MLCAPE 500-1000 J/KG.  THAT WILL BE JUXTAPOSED WITH NARROW AREA OF
   45-55 KT EFFECTIVE SHEAR MAGNITUDES THAT SHOULD SHIFT EWD GENERALLY
   IN STEP WITH MOST OF CONVECTIVE PLUME.  HOWEVER...FASTER SEGMENTS OF
   SQUALL LINE MAY OUTPACE OPTIMAL MOISTENING...ESPECIALLY ACROSS
   PORTIONS NERN INDIANA AND SERN LOWER MI.  MEANWHILE...WEAK SFC
   INFLECTION POINT AND COLLOCATED MESOLOW WAS ANALYZED OVER SERN MO
   OZARKS...MOVING NEWD ALONG CONVECTIVE BOUNDARY TOWARD SRN/ERN IL. 
   AS SUCH...SEGMENT OF CONVECTIVE BOUNDARY ACROSS PORTIONS ERN
   IL...AND PERHAPS SWRN/CENTRAL INDIANA...MAY STALL OR EVEN RETREAT
   SLIGHTLY NWD.
   
   ..EDWARDS/MARSH.. 04/18/2013
   
   
   ATTN...WFO...CLE...ILN...DTX...APX...LMK...IWX...GRR...IND...
   PAH...ILX...LSX...SGF...
   
   LAT...LON   37119111 37869057 38588940 39628736 41258586 42818579
               43548523 43958382 43708386 43658369 43868345 44028299
               43988269 43528254 42958240 42618254 42328300 41878335
               40988329 39878420 39028548 38578646 38368908 37369040
               37119111