Early Fall Snow Across Minnesota and Wisconsin
By Christopher Dickson on September 20, 2012, 8:00pm
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The first snowfall of the season may occur for parts of Minnesota and Wisconsin Friday night into early Saturday morning. A cold front, currently over Eastern Michigan, will introduce cold air into the upper Midwest and a small storm system will follow behind. The storm system will be caused by a shortwave, a low pressure trough within a larger low pressure trough. Temperatures will be marginally suitable for snow across much of the area, but the areas shown in dark blue have a more favorable forecast for snow and could see a coating.
This is the most recent, 18z, run of the GFS weather model which show snow accumulation over an inch. This is most likely overdone, and the track will likely be slightly north of this.
The area of snow shown in the Upper Panhandle of Michigan is due to a potential for lake-effect snow Saturday night. Lake-effect precipitation is caused by cold air moving over a warm lake. This causes moisture to rise into the atmosphere and cause precipitation in a manner similar to how thunderstorms behave (in fact thundersnow occasionally occurs in more intense bands or squalls).
GFS snowfall map: [http://www.twisterdata.com/]
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