Midwest Overview - June 8-14, 2003

The week of June 8-14 marked a return to an active weather pattern, with substantial rains in the southern Midwest. A large area from St. Louis to western Kentucky received more than 3.5 inches of rain during the week (Figure 1). Northern Wisconsin and much of Michigan also received above normal amounts of rain, leaving only a band from eastern Iowa, through northern Illinois, to southwestern Michigan at less than 75% of normal for the week (Figure 2). The Arrowhead of Minnesota also lacked for precipitation during the week. Unfortunately, these areas were already quite dry. Temperatures were still cool in most of the Midwest during the week, but averaged only 2-5°F below normal in most of the region (Figure 3), as temperatures warmed at the end of the week. Very little change in dryness status was noted for the Midwest in the weekly U.S. Drought Monitor map (Figure 4, National Drought Mitigation Center). The main concern for crop development in the Corn Belt at this time is still the lack of growing degree days to accelerate crop growth.

On June 8th, the remains of a formerly strong low pressure system brought a cold pool of upper air through the northern Midwest, creating enough instability to form strong thunderstorms and accompanying severe hail, wind, and tornado events (Figure 5, Storm Prediction Center). The most severe weather occurred in southern Michigan (Figure 6, College of Du Page), including several short lines of severe cells that spawned 5 tornado touchdowns. While several tornadoes caused damage, including extensive home damage in a neighborhood near Flint, MI, no one was killed in the outbreak. Considerable tree damage was observed, and about 7,000 lost power in Michigan. Storms in Cleveland, OH, disrupted an outdoor art fair, injuring 3, and 15-20 people received minor injuries when a tent collapsed at a Sparta, KY, outdoor concert.

Just 2 days later, on the 10th, a strong low pressure center located in southern Minnesota and Wisconsin brought both a warm and a cold front through the central and southern Midwest. During the morning, a great deal of convective activity and heavy rain fell as the warm front moved through the eastern Missouri and southern Illinois (Figure 7, National Weather Service). A mass of warm and humid unstable air was drawn northward ahead of the front, and a special radiosonde taken at 1 PM in Springfield, MO, displayed highly unstable conditions, including more than 2400 J of CAPE and a Lifted Index of -8.3 (Figure 8, COD). By mid-afternoon, a large mesoscale convective system (MCS) was crossing Missouri (Figure 9, NWS); this cluster of strong thunderstorms continued all the way across to Indiana, as can be seen in the severe weather reports map for the day (Figure 10, SPC). The St. Louis area was especially hard hit, with more than 110,000 homes and businesses without power, and many downed trees. A blue-green cast to the late afternoon light was noted as the storms arrived, and lightning strikes were frequent. Straight-line winds were estimated to have reached up to 100 mph at Scott Air Force Base as the MCS moved through the area. About 13,000 lost power in Belleville, IL, and many smaller outages also took place in rural areas. Building damage was spotty, but included an apartment complex with two roofs torn off. A second wave of strong thunderstorms formed with the cold front during the evening of the 10th, bringing more storms and heavy rain to Missouri and Illinois (Figure 11, NWS).

During the last four days of the week and into the next, a stationary boundary set up and moved very slowly from central Illinois to the Ohio Valley. On each day, a different region was affected by a narrow band of nearly stationary convection. On the 11th, the storms not only rained copiously, but were also associated with weak tornadoes across central Illinois (Figure 12, NWS). More than 3,000 people attending a fair near Springfield, IL, had to take cover during the threat of even weak tornadoes, but fortunately, little damage occurred. The zones of convergence moved into central Indiana, then southeastern Indiana, then the Ohio River Valley proper by the end of the period. Some locations in the Midwest received enormous amounts of rainfall this week, including Missouri (Figure 13, NWS) and southern Illinois (Figure 14, NWS). At the end of the period, precipitation accumulations in Indiana, Ohio, and Kentucky (Figure 15, NWS) were initiating flooding along rivers as well as flash flooding. This will be discussed in the next weekly report.