Midwest Overview - May 15-21, 2003

Compared to the first two weeks of May, the third week was rather benign except for a dam failure in the Upper Peninsula of Michigan triggered by rain during the previous period. Precipitation was widespread but fairly light during May 15-21 (Figure 1), with most locations reporting 0.75 inches or more. The heaviest rains occurred near Minneapolis and in the southern third of the Midwest, where 1-3 inches of rain fell. However, in much of Iowa, northern Missouri, central Wisconsin, and northern Michigan, precipitation was below 50% of normal (Figure 2). Since temperatures were below normal by 2-4°F (Figure 3), there was no immediate concern for intensification of drought in these areas. Drought status in the Midwest changed very little from the previous week (Figure 4, National Drought Mitigation Center).

The winter snowfall in the U.P. of Michigan was quite substantial in places this winter, with nearly 200 inches of snow falling around Marquette, MI (Figure 5, NWS-Marquette). Snow melt had just finished for the spring and much of the surface soil was still frozen, so that when 3.62 inches of rain fell on Marquette on May 11 and 12, reservoirs filled with runoff and dams were put under great stress. On May 14, an earthen dam at Silver Lake gave way, releasing an enormous amount of water downstream into the Dead River. The initial surge of water caused the Tourist Park dam to fail at about 3 PM on May 15, sending even more water downstream. Tremendous erosion and damage to land infrastructure and natural ecosystems took place. Many bridges and roads were washed away, and parts of County Road 550 were closed, causing long detours for rural residents working in Marquette (Figure 6, US Army Corp of Engineers). About 1800 people were evacuated downstream of the next dam, the Hoist Dam, but fortunately, this dam held despite being overtopped with water. Still, the excess water continued its destruction all the way to the harbor in Marquette where the river meets Lake Superior. Fortunately, no one was killed in the event, but more than $10 M in damage has already been identified, and one of the major power plants for the U.P. of Michigan was flooded and knocked out of commission in northern Marquette. Residents were being asked to conserve electricity in the meantime, as the amount of power that can be transmitted through power lines into the region is limited. The governor of Michigan has asked the federal government for a disaster declaration.

An upper level low pressure system moved through the lower Mississippi Valley on May 16-17, bringing rain to the extreme southern portions of the Midwest including southern Missouri, southern Illinois, southern Indiana, southern Ohio, and much of Kentucky. An inch of rain was common in this band, with heavier amounts in eastern Kentucky (Figure 7). The recent abundant rainfall in the Midwest did result in some minor flooding of streams and rivers, and ponding of water in fields. The wet fields delayed planting progress in parts of the Midwest, and corn planting is running behind the 5-year average in some areas after a strong early start. A strong cold front moved through the Midwest on May 19-20 accompanied by some showers and thunderstorms, but rainfall was generally light. The exception was south-central Minnesota, which received 1.00 to 1.50 inches of rain. Much cooler and drier weather followed at the end of the period. On the morning of the 21st, low temperatures were below freezing in parts of northern Minnesota, Wisconsin, and Michigan, a larger area was below 35°F, and even Iowa was dominated by minimums below 40°F (Figure 8). The minimum temperature sank to 29°F at Rhinelander, WI.