Storm Prediction Center Mesoscale Discussion 1167

   Mesoscale Discussion 1167
   NWS Storm Prediction Center Norman OK
   0400 PM CDT Wed Jun 17 2026

   Areas affected...eastern Missouri...central Illinois...western
   Indiana

   Concerning...Tornado Watch 342...

   Valid 172100Z - 172200Z

   The severe weather threat for Tornado Watch 342 continues.

   SUMMARY...Tornado threat continues within WW342. A corridor of
   increasing tornado potential may emerge across central Illinois
   during the next couple of hours.

   DISCUSSION...Air mass recovery is ongoing across central Illinois in
   the wake of morning convection south of a boundary of strong
   differential heating. Dew points in the upper 60s to 70s are
   shifting northward back into central Illinois with temperatures
   warming in the 80s. Pressure falls are maximized across this region,
   with strong low-level southerly flow with the strong mass response.
   North of the boundary, elevated supercell structures have developed.
   Within this region STP is approaching 3-5 with effective SRH around
   700 m2/s2 in the 20z RAOB from ILX. Should a supercell be able to
   become surface based tornado potential will rapidly increase.

   Additional watches will need to extend downstream into portions of
   central/southern Indiana in the next hour.

   ..Thornton.. 06/17/2026

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...IND...LOT...ILX...LSX...DVN...

   LAT...LON   39589214 40129157 40369097 40519013 40528888 40388739
               40078709 39768696 39278709 38738725 38678744 38658852
               38578977 38479092 38499143 38669172 38869191 39119207
               39589214 

   MOST PROBABLE PEAK TORNADO INTENSITY...140-170 MPH
   MOST PROBABLE PEAK WIND GUST...65-80 MPH
   MOST PROBABLE PEAK HAIL SIZE...2.00-3.50 IN