The jet stream roaring into the U.S. off the Pacific splits into two distinct branches over the Rockies–one arching north into Canada; the other taking a southern route across Texas and the Gulf and Mexico. It’s a development with significant ramifications for our Midwest weather. By diverting these important bands of steering winds around the Midwest, the movement of the region’s major large-scale weather features has slowed to a crawl. That is to keep some form of easterly wind blowing here well into the weekend — though these winds will tend to “back” more southeasterly in time. That’s especially true over the coming weekend. This shift in direction reduces the time the incoming flow spends over Lake Michigan’s chilly water and permits less penetration of the cool air inland. By late Sunday night, winds here appear likely to shift southerly, cutting off access to lake-cooled air while offering warm, humid Gulf air unfettered access to the Midwest. The result is likely to be this area’s longest string of warm, humid days of 2007 to date next week.
NOAA-NCEP, NWS-Chicago, Frank Wachowski
WGN-TV/Brad Holz, Thomas Valle
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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.
WGN-TV meteorologists Steve Kahn, Richard Koeneman and Paul Dailey plus weather producer Bill Snyder contribute to this page.
