Monday’s muggy, moisture-saturated atmosphere destabilized explosively as temperatures surged. Destabilization is the term applied by meteorologists when temperatures decline more rapidly than usual with height. It encourages air to ascend vigorously, a process which on Monday converted the 1.5”-2” of water which permeated the lower 3.5 miles of the steamy Memorial Day atmosphere in vapor form into banks of towering thunderstorms—some up to altitudes of 55,000 feet. At that height (though it was hot at ground level) readings dropped below -80° F. Much of the day’s t-storm clouds were below freezing, fostering the growth of huge hailstones—some as large as 1”—which crashed to Earth in driving downpours and wind gusts to 75 m.p.h. like those in Crete, Ill., and Schererville, Ind.
Kankakee County was the epicenter of the area’s heaviest rain. Doppler radar estimates topped 4” in parts of the county. Water stood 2-3 feet deep in Bourbonnais.
--Tom Skilling, WGN-TV Meteorologist
WGN-TV Chief Meteorologist Tom Skilling and the WGN Weather Center staff provide daily coverage of weather in the Chicago area.
