Midwest Weekly Highlights - December 18-24, 2006
Very mild weather retained a hold on the Midwest this week. Temperatures for the region ranged from 8°F above normal in southwestern Missouri to15°F above normal in northwestern Minnesota, with most of the Midwest falling in the range of 10°F to 12°F above normal (Figure 1). It was also a very wet week for most of the Midwest, with much of the region receiving normal to well above normal precipitation. The heaviest precipitation, reaching 300 percent of normal or more for the week, fell in a wide band from northern Missouri through southern Minnesota, and east through Wisconsin (Figure 2). Northern Minnesota, where Extreme drought has been persistent (Figure 3), was on of two areas to reviled well below normal precipitation this week. The other dry area was southwestern Kentucky, where precipitation was generally around 60 percent of normal. Significant snowfall this week was limited to north-central Wisconsin and the western Michigan Upper Peninsula (Figure 4).
Quiet Start, Stormy End
As the week began high pressure was building into the Midwest behind a slow-moving cold front pushing south of the Ohio River. A few scattered showers accompanied the front from southwestern Missouri through southern Illinois, but most of the region was enjoying sunny weather. By December 19 the center of the high pressure system hade moved into the eastern U.S. and mild air began its return on southwesterly winds. High temperatures on December 19 were generally in the 40s throughout the Midwest, with a few readings in the low to mid 50s south of the Ohio River. Hibbing, MN reached a new record high of 42°F, breaking the old record of 35°F set in 1988. A number of locations in Minnesota tied record highs for December 19, including International Falls, MN with a high of 38°F (first set in 1953).
On the morning of December 20 a new storm system was developing over Oklahoma, and rain was spreading northeastward through Missouri into Illinois. The storm center lifted northward into Kansas by December 21, and by midday winter weather-related watches and advisories were in place from central Colorado into northeastern Minnesota (Figure 5). A mix of rain, sleet, freezing rain, and snow affected northwestern Iowa and southwestern Minnesota causing some travel problems. (This is the same storm system to drop 2 to 3 feet of snow on Denver). To the south of the wintry mix, temperatures soared into the mid 50s and rain was widespread.. The storm center moved east into northern Illinois on December 22 (Figure 6, Unisys). By the morning of December 22, a swath of precipitation greater than one inch had fallen across much of eastern Illinois and western Indiana, and also across eastern Iowa (Figure 7). This round of heavy rain caused levels to rise on a number of smaller rivers in Illinois and Indiana, and flood warnings were issued for the Little Wabash in Illinois and Indiana and for the Sangamon in central Illinois. The lower Illinois River remained above flood stage from the snow melt from early in the month and subsequent rainfall.
As the storm slowly moved northeast through the Midwest to a position over eastern Lake Superior by the morning of December 23, winter storm warnings and advisories were posted across much of Minnesota and the northern half of Wisconsin (Figure 8 ). A heavy, wet snow began falling on the night of December 22 and continued until the morning of December 23. The accumulation of 6 to 8 inches of heavy, wet snow snapped trees limbs and power lines. Up to 30,000 customers of Wisconsin Public Service Corp. lost power, about half in the cities of Wausau (Marathon County) and Stevens Point (Portage County). By Saturday power had been restored to almost half of those customers as more that 100 crews worked to repair the damage. Heavy snow also fell in the western Michigan U.P., where up to 12 inches of snow accumulated (Figure 9).
Weak high pressure centered over the Ohio Valley produced seasonably mild weather across the Midwest on Christmas Eve. A white Christmas was out of the question for most of the region, with snow on the ground only over far northern and southern Minnesota, central Wisconsin and the Michigan U.P. (Figure 10).