December 4-5, 2007 Snow/Lake Effect Snow Map and Summary...Updated 12/06

An Alberta-Clipper low pressure tracked from South Dakota, to Iowa, to southern Illinois, to southern Indiana from the morning of Tuesday, December 4 to the early morning on Wednesday, December 5.  Widespread moderate snow to the north of this storm track produced a general 3 to 6 inches across the southwestern two thirds of Wisconsin, with locally higher amounts across southern Wisconsin.  Less than an inch of snow fell across northeast Wisconsin. 

As the system passed south of Wisconsin, cold north and northeast winds over lakes Michigan and Superior produced additional lake effect snows, across northwest Wisconsin, along the Bay of Green Bay, and southeast Wisconsin Tuesday night and Wednesday morning.   Across southeast Wisconsin, additional snow amounts of 2 to 4 inches resulted from the quick-hitting, very heavy lake bands.  Milwaukee’s morning rush hour on the 5th was significantly impacted, and Milwaukee’s General Mitchell International Airport was even closed for a time during the heaviest lake effect snows.  Storm totals near Lake Michigan ranged from 7 to over 11 inches, with the highest amounts in Kenosha County.  In northwest Wisconsin, snowfall totals ranged from 9 inches in Superior (Douglas County) to 17 inches in the western part of the city of Duluth, Minnesota!  Near the city of Ashland, 13.2 inches was measured.  Four inches of snow was measured Dyckesville in far northwestern Kewaunee County on the shore of the Bay of Green Bay.

Below is a map of snowfall from December 4th through the early afternoon of December 5th.

Dec 4-5 Wisconsin Snowfall

It is unusual to see lake-effect snow occuring within an 18-hour period in northwestern Wisconsin, in the Bay of Green Bay, and along the western shore of Lake Michigan because it is difficult to get a sustained onshore northeast wind in those areas with cold air aloft and relatively warm water temperatures.  Usually there is enought variation in wind direction such that the lake-effect machine is turned on in only one or two of the four locations.  It is somwhat rare to see lake-effect snow in the Bay of Green Bay.  Below are radar images of the storm from the WSR-88D Doppler radar sites at Milwaukee, Duluth, and Green Bay NWS offices. 

The radar image below shows the widespread system snow and lake-effect snow (green band just off-shore) over the NWS Milwaukee forecast area at 11:01 P.M. December 4th:

Milwaukee radar system snow

Below is the radar image from the NWS Milwaukee office of the heavy lake-effect snow squalls affecting the far eastern parts of Racine and Kenosha Counties at 8:56 A.M Dec 5th:

Milwaukee radar image of the lake effect snow

Below is the NWS Duluth radar image of the lake-effect  snow  band (green colors) affecting Superior and Duluth at 3:29 P.M Dec 4th.  If you look more to the east near Ashland you can see some specks of darker blue extending out over Chequamegon Bay.  These blue specks are the tops of another lake-effect snow band that was affecting the Ashland area.  Otherwise, the Alberta-clipper system snow was widespread over the remainder of Minnesota and Wisconsin, as shown by the other blue and green colors:

Duluth radar image of lake effect snow

Finally, below is the NWS Green Bay radar image of the very unusual lake-effect snow moving inland from the Bay of Green Bay at 12:51 P.M. Dec 4th.  Snowfall in the Green Bay to Dyckesville are ranged from 2 to 4 inches.

Green Bay radar image of bay effect snow



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