MESOSCALE DISCUSSION 0504
   NWS STORM PREDICTION CENTER NORMAN OK
   0646 PM CDT WED APR 17 2013
   
   AREAS AFFECTED...PORTIONS OF CENTRAL/NRN IL...PORTIONS OF NRN IL
   
   CONCERNING...TORNADO WATCH 118...
   
   VALID 172346Z - 180115Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 118 CONTINUES.
   
   SUMMARY...THE THREAT FOR SVR TSTMS AND PERHAPS A TORNADO CONTINUES
   ACROSS MAINLY EAST-CENTRAL IL/WEST-CENTRAL IN PORTION OF WW.
   ELSEWHERE...CONVECTIVE OUTFLOW WILL INCREASINGLY STABILIZE BOUNDARY
   LAYER RESULTING IN MAINLY A LARGE HAIL THREAT THROUGH 05Z.
   
   DISCUSSION...A COMPLEX SURFACE PATTERN EXISTS ACROSS WW AREA AS
   CONVECTIVE OUTFLOWS HAVE MASKED THE WARM FRONT RESULTING IN A
   REDUCED TORNADO THREAT OVER MUCH OF THE WW AREA. AT 23Z SURFACE
   OBSERVATIONS AND RADAR TRENDS SHOW A NWWD-MOVING OUTFLOW BOUNDARY
   FROM JUST SOUTH OF GUS TO HUF. FARTHER WEST...CONVECTIVE OUTFLOW HAD
   SPREAD EAST TO ROUGHLY FROM NEAR TAZ TO 25 S OF SBN. TSTMS WITHIN A
   SMALL CORRIDOR BETWEEN THESE TWO OUTFLOWS MAY BRIEFLY POSE A RISK
   FOR LOW-LEVEL ROTATION BEFORE BEING UNDERCUT BY OUTFLOW BY 0030Z.
   AFTERWARD...EFFECTIVE SHEAR VALUES AVERAGING 45-55KT AND MUCAPES
   FROM 500 J/KG OVER NRN PORTIONS OF WW AND TO AROUND 2000 J/KG OVER
   SRN PORTIONS WOULD FAVOR MAINLY LARGE HAIL. AN ISOLATED DAMAGING
   WIND GUST CANNOT BE RULED OUT WHERE STRONG WINDS CAN PENETRATE THE
   SHALLOW CONVECTIVE OUTFLOW OVER SRN PORTIONS OF WW AREA.
   
   ..BUNTING/THOMPSON.. 04/17/2013
   
   
   ATTN...WFO...IWX...IND...LOT...ILX...LSX...DVN...
   
   LAT...LON   41418559 40058601 39658713 39338911 39508980 39699057
               40499068 41138742 41418559