Midwest Weekly Highlights - February 15-21, 2009
The third week of February was cold across the entire Midwest, with dry weather in the southern half of the region and wetter than normal weather in the northern half. Most of the precipitation in the northern half of the region was from snow.
Temperatures this week ranged from 3°F to 14°F below normal across the Midwest (Figure 1). The coldest weather was found in the northern half of Minnesota where temperatures were 8°F to 14°F below normal. Another core of colder temperatures was centered over southeastern Iowa, where departures were 8°F to 9°F below normal.
Precipitation across the region was well below normal this week with a few exceptions (Figure 2). Precipitation was normal to three times normal from northwestern Minnesota to central Wisconsin and then into the Michigan U. P. Precipitation was also normal for the week in northwestern Indiana and in far southeastern Kentucky. Very little, if any, precipitation fell from western Missouri across the the southern half of Illinois. Snowfall was normal to well above normal across the northeastern half of the region, and accounted for most of the precipitation this week (Figure 3). At the end of the week four or more inches of snow covered the ground across much of Minnesota, Wisconsin, extreme northern Illinois, parts of northern Indiana, and northern lower Michigan (Figure 4).
Moderate to severe drought continued to be depicted across the northern two-thirds of Wisconsin this week on the U.S. Drought Monitor (Figure 5). There was little change from the previous week as precipitation occurred across most of the affected area.
High pressure drifted across the Midwest the first few days of the period bringing cold and dry weather to the region. On the morning of February 17 the high pressure system had drifted to the east coast and low pressure was strengthening over the Central Plains. On the morning of February 18 the low was located in western Illinois just north of St. Louis (Figure 6) and was producing a broad swath of precipitation across the northern half of the region. Most of this was snow, with some sleet reported in Illinois and central Indiana. The heaviest snow fell across Wisconsin, northeastern Illinois, in northern lower Michigan, and downwind of Lake Michigan in northern Indiana where 3 to 5 inches of snow was common (Figure 7). The low continued moving to the northeast into southern Quebec the next 24 hours, but strong northwestern winds streaming across the Great Lakes produced more lake-effect snow in Michigan, Indiana, and Ohio (Figure 8). Snowfall for the storm exceeded 8 inches in some areas, especially in the lee of the lakes.
Clipper Brings More Snow
An Alberta clipper racing across the Midwest late on February 20 and on February 21 brought more now to much of the northern Midwest (Figure 9). Thunder was reported with the snow in parts of north-central Illinois with snow falling at more than 2 inches per hour. Two to four inches of snow fell from Minnesota into northern Illinois by the morning of February 21 (Figure 10). Snow continued during the day across Michigan, northern Indiana, and Ohio, with light snow reported as far south as central Kentucky. The heaviest snow was in lower Michigan where 3 to 8 inches of snow accumulated.
Ice Jams Cause Flooding
Ice jams continued to pose a flooding threat on rivers in Michigan and northern Illinois at the end of the week.