Supercell thunderstorms produce tornadoes, large hail and damaging winds across northern/central Illinois and northwestern Indiana
1-minute Mesoscale Domain Sector GOES-19 (GOES-East) Visible and Infrared Window images (above) included time-matched plots of SPC Storm Reports — which showed supercell thunderstorms that produced several tornadoes, hail as large as 2.50″ in diameter and wind gusts as high as 85 mph across parts of northern/central Illinois and far northwestern Indiana on 11 June 2026. Of the 20 confirmed tornadoes so far across the NWS Chicago forecast area, initial storm surveys have found EF3 damage in Streator, Illinois and Kouts, Indiana.
1-minute GOES-19 Visible and Infrared Window images that included plots of GLM Flash Points (below) highlighted the abundant lightning activity associated with these thunderstorms. Surface observations also supported the satellite depiction of a relatively cloud-free cold pool (created by outflow from a decaying convective complex across northeastern Illinois earlier in the day) — and the upscale growth and tornado production of discrete supercell thunderstorms appeared to increase as they moved eastward and interacted with that residual boundary.
Plots of rawinsonde data from Lincoln, Illinois (location) at 1800 UTC and 2100 UTC (below) displayed a marked increase in the atmosphere’s instability and shear parameters during that 3-hour period — and an elevated mixed layer became well-defined. At the surface, Lincoln was located within the warm, moist air that was surging northward toward the aforementioned residual convective outflow boundary.
