The muggy, haze-filled atmosphere which greets Chicagoans Thursday is the most humid here in nearly two weeks. It is literally dripping with tropical moisture and has been swept north off the Gulf of Mexico by well-organized southerly winds blowing over nearly 2,000 miles of terrain—from the Gulf north to Canada’s James Bay. Computer moisture profiles Thursday indicate a deep layer of the air mass is in a state of near saturation—i.e. holding nearly all the moisture it can—extending from the ground to heights of more than 19,000 ft. Showers erupt with regularity in this sort of environment and any breaks for even modest spells of passing sun are likely to produce enough heating to encourage t-storm development.
Late Wednesday’s spotty but gusty t-storms towered to 31,000 ft. tall and produced brief downpours and 40+ m.p.h. winds. Better organized thunderstorms arrive Friday.
--By Tom Skilling, WGN-TV Chief Meteorologist
WGN-TV Chief Meteorologist Tom Skilling and the WGN Weather Center staff provide daily coverage of weather in the Chicago area.
