Midwest Weekly Highlights - December 15-21, 2003

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The third week of December was generally dry and mild across the Midwest.  The heaviest precipitation was found in western Minnesota and northwestern Iowa, where the prevailing storm track favored precipitation. Precipitation across most of the Midwest for the week was less than 50 percent of normal (Figure 1), and much of what did fall was snow. Snow was heaviest in Minnesota and in the typical lake-effect areas of Michigan and Wisconsin (Figure 2). Temperatures this week were generally above normal, ranging from 1F to 2F above in the central Midwest to as much as 8F to 10F above normal in northwestern Minnesota (Figure 3). The only cooler than normal portion of the Midwest was southern Indiana, most of Ohio, and Kentucky, where temperatures averaged one -1F to -4F.

A fast-moving low pressure system moved through the Midwest on December 15-16 producing a wide area of 2-6 inch snowfall across Iowa, Minnesota, and Wisconsin (Figure 4). Precipitation to the south was sparse as moisture available to this system was limited, with some light rain in Missouri, Illinois and Indiana.  On December 18-19 an “Alberta Clipper” system raced southeastward out of Canada and deposited a band of 1 to 3 inches of snow from western Minnesota through Iowa, Illinois, and central Indiana (Figure 5). At the same time strong northwesterly flow over the upper Midwest brought more lake-effect snow to the eastern shores of Lake Michigan.