Midwest Overview - April 17-23, 2003

The week of April 17-23 marked a welcome return to normal to above normal precipitation in most of the Midwest. Drought stricken areas of northwestern Missouri and central Minnesota and Wisconsin received 1.50 to 3.00 inches of rain (Figure 1). Precipitation exceeded 200% of normal for the week in all of Minnesota, the northern two-thirds of Wisconsin, the northern half of Michigan, northwest Missouri, and parts of Kentucky and the Ohio River Valley (Figure 2). Unfortunately, some of the dry areas in the eastern Corn Belt, in northern Illinois and Indiana, received as little as 50% of normal rain. The temperatures in the region varied widely over the course of the week, with warm air penetrating the southern half of the region on several days but generally staying out of the northern Midwest. The coldest temperatures, 3-7°F below normal, were found in the northwestern states of the region, while the warmest temperatures, 1-4°F above normal, were found in the southeastern portion of the Midwest (Figure 3). The was substantial drought relief this week in much of Minnesota, Wisconsin, and Michigan, and parts of Iowa, Missouri, and Illinois. Unfortunately, drought severity increased in northern Illinois and Indiana, and southern Wisconsin (Figure 4, National Drought Mitigation Center); these dry areas missed the heavier rains.

During the first 4 days of the period, heavy rains affected at least some part of the Midwest every day. The week began with a very slow moving occluded low pressure system crossed the Ohio Valley for two days. On April 19, a large area of more intense low pressure developed over the Great Plains, with its strongest center in Oklahoma (Figure 5, U of Illinois Department of Atmospheric Science). This low moved more rapidly than the previous one, reaching the upper Midwest by the middle of the next day (Figure 6, UI DAS). This placed the central and eastern Midwest in an ideal situation for frontally triggered thunderstorms and strong winds on the 20th. The storms started to break out in late morning, and by early afternoon, there were a number of severe storms visible on radar from southern Illinois and western Kentucky, through Indiana and Ohio, into southern Michigan (Figure 7, NWS). Small lines of severe thunderstorms with some embedded supercells developed, with the largest number of these in Indiana (Figure 8, NWS). More than 100 severe weather reports were made in the Midwest on the 20th (Figure 9, Storm Prediction Center), including one tornado in each of Indiana and Kentucky that did little damage in rural areas.

Kentucky was hardest hit in terms of power outages, with more the 27,000 customers in the north central part of the state losing electrical service due to high straight line winds. Many locations in Indiana and Ohio reported 60-70 mph winds and large hail. The Columbus, Ohio, suburb of Hilliard had six inches of hail accumulated on the ground, with significant damage to cars and roof shingles. A 109 mph wind gust was measured just north of Springfield, Ohio; about 2,500 lost power in that area. Further north, in Michigan, high winds downed trees in the Detroit Metro area, cutting off power to more than 10,000 customers, including some whom had power off for a week earlier in the month due to an ice storm. The most significant single damage report was the loss of a 272-foot electrical tower on the Canadian side of the St. Clair River that flows between Ontario and Michigan. Shipping traffic was closed for about 24 hours due to two of the large power lines falling into the water and one other dangling at about 50 feet off the river. At least 12 commercial freight vessels were held up on the transit from Lake Huron to Lake Erie, and power imports from Canada to the Midwest needed to be rerouted.

The last few days of the week, the Midwest was under the influence of cool, dry conditions associated with a Canadian high pressure center. Youngstown, Ohio, set a low temperature record on the morning of the 23rd, reaching 26°F that morning. Several other locations, including Cleveland, tied their low temperature records that morning, and frosts and freezes were widespread. During the evening on the 23rd, precipitation from another southern Plains low pressure system entered western Missouri; this will be examined in the next update.