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