Dear Tom,
I realize Chicago is not in a location conducive to epic lake-effect snowstorms. Cold air moving across Lake Michigan usually happens from the northwest and the opposite side of the lake is favored. What is Chicago’s largest lake-effect snowfall and what conditions need to be in place?
Evan Pollock, Chicago
Dear Evan,
Chicago’s heaviest lake-effect snows occur when very cold air slowly traverses the full length of Lake Michigan from northeast to southwest, and when that situation persists for many hours.
In addition, cold air must be in place across Chicago so that relatively warmer but snow-bearing winds coming in from the northeast ride up and over the ground-level cold air. On Dec. 19, 1973, lake-effect snow accumulated 5-12″ over Chicago proper and 12-25″ across Lake Co. (Ill.) north to Green Bay, Wisc.
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Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN-TV News at noon and 9 p.m.
Write to: ASK TOM WHY, 2501 Bradley Pl., Chicago, IL 60618 or asktomwhy@wgntv.com (Mail volume precludes personal response.)
WGN-TV meteorologists Steve Kahn, Richard Koeneman and Paul Dailey plus weather producer Bill Snyder contribute to this page.
