Mesoscale Discussion 1036
   NWS Storm Prediction Center Norman OK
   0325 PM CDT Sun Jun 20 2021

   Areas affected...Portions of eastern Illinois and northern Indiana

   Concerning...Severe potential...Watch possible 

   Valid 202025Z - 202230Z

   Probability of Watch Issuance...60 percent

   SUMMARY...There is an increasing severe weather threat late this
   afternoon and into the evening from east-central Illinois into
   northern Indiana.

   DISCUSSION...An MCV has traversed northern Missouri and western
   Illinois through the morning and early afternoon today. The
   convection has been mostly weak, likely due to the stable, capped
   downstream airmass from the overnight MCS in the region. In fact,
   almost all lightning has now ended within this cluster. However, a
   remnant MCV can still be seen in radar imagery from the KILX
   WSR-88D. 

   The 19Z RAOB from KILX shows the stable airmass with MLCIN near -200
   J/kg. However, the hodograph does show decent clockwise curvature
   within the lowest 3 km and moderate mid-level flow. This is likely a
   good proximity hodograph for later storms which are expected to form
   near this MCV later this afternoon/early evening. 

   Despite the lackluster storm development thus far, this is expected
   to change in the next 1 to 2 hours as this MCV moves into east
   central Illinois where the airmass was not worked over by overnight
   convection. In this region dewpoints are in the low 70s with
   temperatures in the mid 80s with the SPC mesoanalysis suggesting
   2000 J/kg MLCAPE. This instability, combined with 45 to 50 knots of
   effective shear per 19Z ILX RAOB and SPC mesoanalysis should be
   sufficient for supercell development. Any supercells which develop
   may have a risk of all hazards including a couple of tornadoes. The
   tornado threat will likely be greatest in a narrow corridor where
   winds are backed to southerly near the MCV and near the warm front
   where low-level vorticity should be enhanced.

   ..Bentley/Hart.. 06/20/2021

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

   ATTN...WFO...IWX...IND...LOT...ILX...

   LAT...LON   39828860 40048872 40738869 41348849 41618788 41638701
               41768622 41718552 41488527 40798527 40108660 40048723
               39728838 39828860