Dear Tom,
Lake Michigan can cause snow, but can it also cause lake-effect rain?
Tim Browning
Dear Tim,
The same processes that generate lake-effect snow can also produce rain, except that air temperatures must be mild enough to bring rain rather than snow.
Lake-effect precipitation develops when lake water temperatures are at least 20(degrees) warmer than air traversing the lake, a temperature differential sufficient to destabilize the air and generate precipitation–usually snow. Lake-effect rain occurs mainly during the autumn season’s first strong cold outbreaks in October and November.
Case in point: yesterday and today. So cold is the air now that a temperature differential of nearly 50(degrees) exists between Lake Michigan’s surface water and the air a mile up–instability sufficient to produce thunderstorms!
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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.
