Midwest Weekly Highlights - December 25-31, 2006
The month ended with unseasonably mild weather continuing through the last week. The largest departures were found in the upper Midwest, from northwestern Minnesota through central Illinois, where temperatures ranged from 14°F to 20°F above normal (Figure 1). Temperatures across the southern and eastern half of the region ranged from 6°F to 12°F above normal. On most days this week actual minimum temperatures were well above what the normal maximum temperatures are for this time of year. The only portions of the Midwest with overnight temperatures consistently below freezing this week were northern Minnesota, northwestern Wisconsin, and the Michigan UP.
Precipitation this week was plentiful for most of the region except for the northeastern quarter. Precipitation was more than four times normal in western Minnesota south through western Iowa, and normal to well above through the Ohio Valley (Figure 2). Much of the precipitation in western Minnesota across the northern Midwest was snow (Figure 3), but everywhere else it was rain. A number of smaller rivers in Illinois, Indiana, and Ohio remained near or at flood stage this week with the continuation of abundant precipitation. The precipitation in the upper Midwest helped to prevent dry conditions from getting any worse, but there will be little inroads to alleviating the Extreme Drought across the upper Midwest without continued above normal precipitation into spring (Figure 4).
Christmas Day Rain
A storm system moving out of the southern United States affected southeastern portions of the Midwest on Christmas Day. Rain fell across southern Illinois, Indiana, and much of Ohio (Figure 5). Rainfall amounts ranged from 0.50 to 1.00 inch in southern Illinois, Indiana, and eastern Ohio, and 1.00 to 1.50 inches in western Kentucky. As cold air was pulled in behind the storm, a few flurries flew over Illinois and western Indiana, while snow accumulated one to two inches over parts of eastern Indiana and western Ohio. In addition this this small area, only the northern quarter of Minnesota eastward into the Michigan UP enjoyed a white Christmas this year (Figure 6).
Large Storm Closes Out 2006
The middle portion of the week was uneventful for most of the region as high pressure drifted through the Midwest. Some snow fell across southern Minnesota and central Wisconsin along a stationary front on December 27, with amounts of 1.5 to 2.0 inches in the heaviest parts of the band (Figure 7). Clouds began to spread back over the Midwest late on December 28 as yet another storm system began to spin up over the southwestern United States. As it moved toward the Midwest, this system produced more heavy snow and blizzard conditions over the Central Plains. On December 31 the storm was centered over southwestern Iowa, with snow and blowing snow causing travel problems from western Minnesota south through western Iowa (Figure 8). Rain fell south and east of the storm center (Figure 9). As the upper level low pressure system rotated through the Midwest late in the day, thunderstorms broke out across central Illinois (Figure 10), producing some end-of-the-year "fireworks", gusty winds, and pea-sized hail. A band of 4 to 8 inches of new snow covered parts of Iowa and Minnesota in the wake of the storm (Figure 11)