Midwest Weekly Highlights - January 1-7, 2009

A Mild Start to the Year

Temperatures across the Midwest the first week of January were generally colder than normal north, and warmer than normal south. Normal to below normal temperatures occurred across Minnesota, Wisconsin and Michigan, ranging from near normal at the southern edge of this region to as much as 10°F below normal in northwestern Minnesota (Figure 1). In the southern half of the Midwest temperatures ranged from near normal north to 5°F above normal from southern Missouri eastward through southern Kentucky.

A significant portion of the Midwest was dry much of the first week of January. The only areas with above normal precipitation this week were northern Minnesota and the southeastern half of Kentucky (Figure 2). The precipitation was especially welcome in Kentucky where up to 4 inches of rain put a dent in the drought conditions there. The US. Drought Monitor for January 6 (Figure 3) still depicts Moderate drought in Kentucky, but does not reflect the significant rain at the end of the week. There was little change in the extent of the drought conditions in north-central Wisconsin.

Snowfall this week was limited to the northern quarter of the region, with the heaviest in northern Minnesota and the Michigan U.P. Snow cover at the end of the week was 12 inches or more from south central Minnesota across central Wisconsin and the northern half of lower Michigan (Figure 4).
 

Freezing Rain and Drizzle Pester Central Midwest

Although temperatures were mild by January standards, the weather was still cold enough to produce wintry precipitation. A number of generally weak weather systems moved through the Midwest this week accompanied by snow and freezing rain and/or drizzle.

The first of these systems moved through the upper Midwest on January 1-2 (Figure 5). This brought snow to northern Minnesota, Wisconsin, and Michigan. Two to four inches fell in a band north of the low (Figure 6), with a few higher lake-enhanced amounts. Snow amounts of an inch or less fell in central and southern Wisconsin.

The second and more troublesome system began its March through the Midwest on January 3 (Figure 7). The path of this low was considerably further south than the previous system and produced light freezing rain north of its path through the central Midwest. By late on January 3 freezing rain was falling across Iowa eastward into northern Illinois and southern Wisconsin just north of a warm front. The freezing rain turned highways into skating rinks and there were numerous accidents. One fatality was reported in Dodge County, Wisconsin as a result of the icy conditions. South of the front, temperatures soared into the low 70s as far north as central Missouri and into the 60s in the Ohio Valley (Figure 8). By the morning of January 4 the low pressure system was located over the southern end of lake Michigan and colder air was pouring into the western half of the region. Rain continued ahead of the front in Ohio and Kentucky during the day. By early evening the front had moved through the entire region bringing most of the rain to an end.
 

Some Ice and Heavy Rain in Ohio Valley

The third system to affect the Midwest this week was already taking shape as the previous system exited the region. On the morning of January 6 a wave of low pressure developed along the cold front, and that combined with an upper level disturbance produced a large shield of precipitation in the southern Midwest. As moisture was pulled northward into the cold air, freezing drizzle and freezing rain developed from central Illinois eastward through Ohio, while light snow fell across northern Illinois, northern Indiana, and southern Michigan. Ice-covered roads led to numerous accidents, including one resulting in a fatality in Indiana. In Kentucky, moderate to heavy rain fell much of the day in the eastern portions of the state, putting a further dent in the drought that has existed there since August (Figure 9). Rainfall in western and central Kentucky ranged from 0.25 to almost 2.00 inches, while in eastern Kentucky rainfall from this storm ranged from 2.00 to more than 4.00 inches at some locations.

SDH