MESOSCALE DISCUSSION 1240
   NWS STORM PREDICTION CENTER NORMAN OK
   0511 PM CDT FRI JUN 19 2009
   
   AREAS AFFECTED...CENTRAL AND NRN INDIANA/SRN LOWER MI/WRN AND
   CENTRAL OH
   
   CONCERNING...TORNADO WATCH 478...
   
   VALID 192211Z - 192345Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 478 CONTINUES.
   
   ISOLATED SEVERE/SUPERCELL STORMS CONTINUE ACROSS NRN INDIANA...WITH
   MORE WIDESPREAD CONVECTION FARTHER W INTO IL.  STORMS WILL CONTINUE
   ACROSS NRN INDIANA AND SPREAD SLOWLY EWD INTO OH...WHILE ADDITIONAL
   CONVECTION SPREADS ACROSS INDIANA -- AND EVENTUALLY OH -- FROM THE
   WEST LATER THIS EVENING.  WITH WW 478 SET TO EXPIRE AT 19/23Z...A
   NEW WW WILL BE REQUIRED.
   
   LATEST RADAR LOOP SHOWS A WELL-ORGANIZED/LONG-LIVED SUPERCELL STORM
   OVER NERN WABASH/NRN HUNTINGTON/SRN WHITLEY COUNTIES...RIDING ESEWD
   ALONG A PRE-EXISTING OUTFLOW.  THIS STORM HAS GONE THOUGH A COUPLE
   OF LOW-LEVEL MESOCYCLONE CYCLES...AND EXPECT THIS TO CONTINUE --
   ALONG WITH AN ONGOING SEVERE/TORNADO THREAT.  FARTHER NW...A
   SECOND/WEAKER SUPERCELL HAS DEVELOPING ALONG THE REAR-FLANK OUTFLOW
   FROM THE MAIN STORM.  
   
   WITH THE BACKGROUND ENVIRONMENT -- FEATURING MODERATE INSTABILITY
   AND AMPLE VEERING/SHEAR WITH HEIGHT -- SUPPORTING A CONTINUATION OF
   ISOLATED SUPERCELLS ACROSS INDIANA...A NEW WATCH WILL BE ISSUED TO
   REPLACE WW 478.  ADDITIONALLY...THIS WATCH WILL EXTEND EWD INTO WRN
   AND CENTRAL OH...AS THE ESEWD PROGRESSION OF ISOLATED SEVERE STORMS
   WILL LIKELY BE FOLLOWED LATER THIS EVENING BY A LARGE/WELL-ORGANIZED
   MCS NOW ORGANIZING OVER NWRN IL...WHICH WILL LIKELY BE ACCOMPANIED
   BY A WIDESPREAD DAMAGING WIND THREAT.
   
   ..GOSS.. 06/19/2009
   
   
   ATTN...WFO...RLX...CLE...ILN...DTX...IWX...IND...LOT...
   
   LAT...LON   41678723 42078666 41808426 41318284 39288258 38988360
               39348712 41678723