April 18-30, 2001:

The period from April 18-30 was wet in the northwestern Midwest, especially in the Upper Basin of the Mississippi River. Considerable amounts of rain fell during this time (Figure 21) on areas already in full flood from earlier rains and the recent melting of a heavy snow pack. At the same time, the southern and southeastern portions of the Midwest received well below normal amounts of rain (Figure 22), and drought conditions rapidly intensified. The percentage comparison to normal shows the extremity of the pattern, with large areas of Minnesota and northwestern Wisconsin receiving 300-400% of normal rainfall for the period, while large areas of Missouri, Illinois, Indiana, and Kentucky received less than 25% of normal (Figure 23). For the most part, temperature levels were seasonable to mild; one brief cold period on April 22-24 coincided with a Great Plains spring snow storm that brought up to 6-12 inches to portions of northwestern Minnesota (Figure 24). However, the northwestern two-thirds of the region remained above normal for the period due to frequent influxes of warm, humid air with the strong low pressure centers that brought the recent rains (Figure 25). Only the southeastern Midwest was a bit below normal in temperature during this period.

Just as the period began, the Mississippi River reached its first peak in Winona, MN, on April 17. The flood crest continued down the river to Dubuque, IA, on April 21; Bellevue, IA, on April 22; Fulton, IL, on April 24; Davenport, and Muscatine, IA, on April 25; and Burlington and Keokuk, IA on April 26. More than 300 miles of Mississippi River length was flooding at higher than 5 feet above flood stage at the end of the month (Figure 26, NWS). The Davenport flood stage was especially important due to the city's dependence on temporary earthen and sand bag dikes in place of a permanent flood wall. While considerable flooding occurred along the river, including the inundation of the local minor league baseball park, temporary dikes held at a crest of 22.32 feet, just a few inches shy of the 1993 record of 22.6 feet (Figure 27, U.S. Army Corp of Engineers). Since the sand-bag dikes were raised to only 23 feet, it was indeed very good fortune that the rain stopped when it did. However, there were lingering high water stands through the end of April, and the upper Mississippi has experienced a secondary flood crest almost as high as the first after rains on April 21-22. For example, at St. Paul, MN, the Mississippi River returned to the previous high water mark at the end of the month. In some places, sand-bag dikes did fail, or flooding took place around barriers or under barriers through local storm water systems. The event continues into May, as long as high water remains and the possibility for more rain continues.

The drought growing in the southern and southeastern Midwest may also have long term consequences for agriculture, especially as it appears to be spreading to the north and south from the axis of the Ohio River Valley. The May 1 U.S. Drought Monitor (Figure 28, National Drought Mitigation Center) showed the increasing area that is under D0 (abnormally dry) and D1 (moderate drought) status. Parts of eastern and western Kentucky are even drier, with stream flow reaching record lows on some rivers (Figure 29, USGS) and Climate Prediction Center soil moisture model estimates below the 5th percentile (Figure 30, CPC). Corn germination has been delayed in much of western Kentucky by a total lack of topsoil moisture, according to the Agricultural Extension service at the University of Kentucky. Recent heavy storms that have caused flooding in the Mississippi Basin have not brought any rains to the drought area, only days with strong, warm winds that accelerate soil drying. Without significantly above normal rains in the coming weeks, the drought will rapidly intensify.