Midwest Weekly Highlights - December 22-31, 2003

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2003 ends with mild weather

Mild weather overspread the Midwest the last 10 days of December. Two major weather systems moved through the region, dropping snow on northern portions of the Midwest and heavy rain in a swath through the central portion of the region.

Temperatures for the period December 22-31 were much above normal, ranging from 14F above normal in northern Minnesota to 4F above normal in southeastern Ohio (Figure 1).  The temperature departure pattern for the month of December was much the same, with departures 8F above normal in northwestern Minnesota to near normal in southeastern Ohio (Figure 2).

Precipitation during the period varied greatly across the region. Southern Minnesota and Iowa, which have been in drought for much of the last six months, continued to miss out on the precipitation with less the 25 percent of normal precipitation for the 10-day period (Figure 3).   The picture is a little better when looking at the entire month, with much of Iowa receiving 75 percent or more of normal precipitation. However, a large portion of northeastern Minnesota received less than half the normal December precipitation (Figure 4).  The heaviest precipitation December 22-31 fell from southwest Missouri through central Illinois, much of Indiana, northwest Ohio and southeast lower Michigan.  Precipitation averaged 200 percent of normal or more for the period.  Snowfall for the month was well below normal across northern Minnesota, much of Wisconsin, Illinois, Indiana, and lower Michigan (Figure 5).  

Prospects for a White Christmas rapidly disappeared as an upper level trough developed over the nation’s midsection, keeping most of the Midwest under the influence of southwesterly flow aloft (Figure 6, HPC/NCEP ). This pattern helped draw mild air well northward into the Midwest ahead of a developing low pressure system.  The storm moved through the region on December 22-23, producing heavy rain in a band from southwestern Missouri through central Illinois into central Indiana (Figure 7). One to two inches of rain fell in this region, and caused lowland flooding along the Wabash River in Illinois and Indiana.  As the storm departed, cold air traversing the relatively warm waters of the Great Lakes resulted in some lake effect snows in northern Indiana and western Michigan on Christmas Eve, while more general but lighter snow fell across lower Michigan, central Indiana, and Ohio (Figure 8). 

Another cold front entered the Midwest on December 28, very similar to the system on December 22.  A strong flow of moisture into this system from the Gulf of Mexico fueled more rain ahead and along the front.  This system produced a band of 1.00 to 1.50 inch rainfall from southeastern Missouri into central Illinois and northwestern Indiana, many of the same areas which received heavy rain a week earlier (Figure 9).  The rain resulted in continued lowland flooding along the Wabash and White Rivers in Indiana, and some flooding along the Kaskaskia River in south-central Illinois.