Powerful N/NE winds, which roared into Chicago at more than 30 m.p.h. after a 320-mile trek over the length of Lake Michigan, kept precipitation here in liquid form Wednesday. The "warming" effect of 46-degree lake waters on the lower atmosphere is difficult for most storms to overcome. Not until well after sunset did an injection of colder air begin the transition from rain to snow in the far northwest suburbs. Rain changed to snow at Rockford at 6 p.m., and by 8 p.m. had begun accumulating on colder outdoor surfaces near Arlington Heights, Oak Brook and Mundelein. When snow develops at marginally cold temperatures, flakes often stick together. That process in parts of the metro area Wednesday led to reports of 1-inch diameter snowflakes at a few locations. Wind-driven rains Wednesday totaled more than 2" in parts of the city, including 2.20" at Whitney Young High School. The 1.32" (through 8 p.m.) at Midway was the heaviest since Aug. 22 -- three months ago.
--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.
