Midwest Overview - December 8-14, 2002

The week of December 8-14 was exceedingly dry in most of the Midwest, even in many of the Lake Effect belts. Only the Ohio Valley and Kentucky received precipitation totals beyond one inch of liquid water equivalent for the period (Figure 1). The rest of the Midwest received either well below normal amounts of precipitation, or none at all (Figure 1a). Snow belts generally received less than 5 inches during the week, lower than some locations on the north edge of the storm track (Figure 2). A portion of the southern Midwest snow occurred in the wrap-around trailing a system passing through the southeastern Midwest on the 10th and 11th, while the rest fell on the northern edge of a stronger low following the same path on the 13th and 14th. This second low was responsible for most of the 1-2 inch rain totals in the Ohio Valley and Kentucky. In between, on the 12th and 13th, there was widespread dense fog as the warmer and more humid air moved northward into the region. Temperatures for the week were more than 10°F above normal in the northwestern Midwest, but a few degrees below normal in the southeastern Midwest (Figure 3). International Falls, MN, and Marquette, MI, set new maximum temperature records on both the 10th and 11th. The combination of a complete lack of precipitation and warmer than normal temperatures caused drought conditions to intensify across northern Illinois and parts of Wisconsin, Minnesota, Iowa, and Missouri (Figure 4, National Drought Mitigation Center). The conditions were so dry for the last 60 days in the Upper Mississippi, Illinois, and Missouri basins that the Mississippi River south of St. Louis reached its lowest 10th percentile for river discharge at this time of year. The low river levels impacted navigation severely when dredging became necessary for this stretch of river to continue to be fully navigable.