MESOSCALE DISCUSSION 0525
   NWS STORM PREDICTION CENTER NORMAN OK
   0533 PM CDT THU APR 18 2013
   
   AREAS AFFECTED...A LARGE PART OF INDIANA...WRN AND CENTRAL
   OHIO...NRN KENTUCKY
   
   CONCERNING...TORNADO WATCH 127...
   
   VALID 182233Z - 190030Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 127 CONTINUES.
   
   SUMMARY...THE SVR POTENTIAL IS DIMINISHING ACROSS WW 127. THE WW MAY
   BE CANCELLED EARLY...AND ADDITIONAL WW ISSUANCE WILL BE UNLIKELY
   DURING THE NEXT SEVERAL HOURS.
   
   DISCUSSION...REGIONAL MOSAIC RADAR IMAGERY INDICATES A LOOSELY
   ORGANIZED SQUALL LINE EXTENDING FROM NEAR FORT WAYNE TO INDIANAPOLIS
   AND FARTHER SW INTO SWRN INDIANA. THIS ACTIVITY IS LARGELY
   ELEVATED...AS WSR-88D BASE DATA SUGGEST THAT THE CONVECTIVE OUTFLOW
   HAS PROGRESSED E OF PARENT CONVECTION. WITH THE SQUALL LINE ORIENTED
   MOSTLY PARALLEL TO DEEP SHEAR VECTORS...THIS CONVECTION SHOULD
   MAINLY REMAIN ELEVATED ATOP THE CONVECTIVELY GENERATED COLD POOL.
   WITH AN INFLOW OF ONLY VERY MARGINAL INSTABILITY...THIS ACTIVITY
   SHOULD POSE NEAR-ZERO SVR THREAT AS IT LACKS MORE SUBSTANTIAL
   ORGANIZATION. HOWEVER...AN ISOLATED STRONG WIND GUST CANNOT BE RULED
   OUT NEAR THE INTERSECTION OF THE SQUALL LINE AND AN OUTFLOW BOUNDARY
   ACROSS CNTRL/ERN INDIANA THAT EXTENDS INTO WRN OHIO.
   
   LITTLE EWD DEVELOPMENT/PROPAGATION OF THIS ACTIVITY IS ANTICIPATED
   OWING TO THE VERY LIMITED DEGREE OF INSTABILITY ACROSS ERN INDIANA
   AND OHIO. THIS IS WHERE SFC TEMPERATURES IN THE UPPER 70S TO THE
   LOWER 80S HAVE ALLOWED PBL CIRCULATIONS TO DEEPEN SUBSTANTIALLY. IN
   TURN...THIS HAS ALLOWED THE DRIER AIR MASS E OF THE PLUME OF DEEPER
   MOISTURE/HIGHER PW TO BE MANIFESTED IN LESS THAN 700 J/KG OF MLCAPE
   PER THE MODIFIED 12Z WILMINGTON OHIO RAOB.
   
   ADDITIONAL STRONG CONVECTIVE DEVELOPMENT WILL BE UNLIKELY ACROSS
   INDIANA INTO OHIO...OWING TO THE FOLLOWING FACTORS:
   /1/ A LONG FETCH OF ONLY MARGINAL LOW-LEVEL MOISTURE TO THE S --
   I.E. SFC DEWPOINTS IN THE 50S...
   /2/ THE ONSET OF NOCTURNAL STABILIZATION CONTRIBUTING TO ADDITIONAL
   LESSENING OF PRESENT BUOYANCY AND INCREASING CINH...
   /3/ THE DEEPER FRONTAL CIRCULATION REMOVED WELL TO THE W ACROSS IL
   AND MO...AND
   /4/ WIDESPREAD PRECIPITATION AND ASSOCIATED LOW-LEVEL THETA-E
   DEFICITS PRECEDING THIS DEEPER FRONTAL CIRCULATION.
   
   WHILE SOME STRONGER STORMS COULD EVOLVE LATE IN THE NIGHT IN
   OHIO/ERN INDIANA AS THE NOCTURNAL BOUNDARY LAYER MARGINALLY MOISTENS
   IN ADVANCE OF THE DEEPER FRONT...CINH SHOULD BE TOO LARGE FOR ANY
   SUBSTANTIAL SVR THREAT. AS SUCH...TORNADO WATCH 127 MAY BE CANCELLED
   EARLY...AND ADDITIONAL WW ISSUANCE WILL BE UNLIKELY DURING THE NEXT
   SEVERAL HOURS.
   
   ..COHEN.. 04/18/2013
   
   
   ATTN...WFO...CLE...ILN...LMK...IWX...IND...
   
   LAT...LON   41608330 41358273 39968286 39098363 38408510 38528693
               38948745 40098680 41228521 41618419 41608330