Midwest Weekly Highlights - November 15-21, 2003

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Warm and Wet in the Midwest

The week of November 15-21 was warm over the entire Midwest, and wet over a large swath from southern Missouri to central Michigan. Precipitation for the week reached 3-5 inches in the southeastern half of Missouri and southern Illinois, with the same band continuing northeastward with totals of 1-2 inches (Figure 1). Almost all of Missouri, Illinois, Indiana, and Lower Michigan received more than 200% of normal precipitation for the week (Figure 2). Temperatures were more than 5°F above normal in the entire Midwest, reaching more than 10°F above normal in western Iowa (Figure 3). A lesser band of precipitation brought 0.5-1.0 of rain to some of the drier areas of Midwest in Iowa and Wisconsin, but did not appreciably change the drought status in the region (Figure 4).

One major storm affected the region on the 17th and 18th. As the low pressure approached, a strong influx of warm and humid air brought about a widespread heavy fog on the morning of the 17th (Figure 5, College of DuPage). Flights were delayed for several hours at Chicago's O'Hare Airport, many school districts delayed the start of school in the eastern Midwest, and at least one traffic death in Indiana was ascribed to low visibility. An initial line of precipitation brought a band of rain to Missouri, central Iowa, southeastern Minnesota (Figure 6, COD), but this initial line died out due to a lack of upper air support. When a strong low pressure center approached from Kansas, and the upper trough moved into a favorable position, the line of storms re-formed on the afternoon of the 17th, and brought heavy precipitation to a broad band from southwestern Missouri north to Lower Michigan (Figure 7, COD). This precipitation band shifted eastward through the night, leaving a moist unstable environment in the southern Midwest. Late in the afternoon on the 18th, the low pressure center arrived and triggered an outbreak of severe weather in southwestern Missouri, accompanied by more heavy rain (Figure 8, COD). Total precipitation for both days exceeded 6 inches in some locations in south central-Missouri (Figure 9a, NWS), and 5 inches near St. Louis (Figure 9b, NWS). While severe winds and hail were reported on the 17th in Iowa and St. Louis (Figure 10a, Storm Prediction Center), the worst of the severe weather was on the 18th in southern Missouri (Figure 10b, SPC). The St. Louis area alone had more the 13,000 electricity customers without power. Winds of up to 70 mph were recorded in southwestern Missouri, and light damage occurred due to high winds throughout Missouri. Flash flood warnings were common in Missouri, Illinois, Indiana, and Michigan, but serious or widespread damage was not reported. The week ended with continued warm weather, including some record high temperatures in the mid-60s in Madison, Oshkosh, Appleton, and Manitowec, WI, on the 20th.