Midwest Weekly Highlights - July 11-17, 2003

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A stormy, wet weather pattern continued over much of the Midwest this period.

High pressure dominated Midwest weather the first few days of the period, although there were scattered thunderstorms in northern Wisconsin, the Upper Peninsula, and northern Michigan. Some thunderstorms also moved through eastern Kentucky as a cold front exited the region.  The latter half of the period featured a line of thunderstorms moving across the already waterlogged central Midwest, while the far western portions of the region remained dry.

Precipitation for the week was well above normal from northwestern Wisconsin through northeastern Illinois to southern Indiana to the eastern half of Kentucky (Figure 1).  Rainfall was also plentiful across the northern half of Michigan.  In sharp contrast, much of Iowa, northern Missouri, and western Illinois remained very dry during the week.  For the first 17 days of July, rainfall is above normal for most of the Midwest except for much of Missouri, far southern Illinois and western Kentucky, and northeastern Wisconsin. (Figure 2).  Much of central Indiana has received more than 6 inches of rain so far this month (Figure 3), with a number of locations in northern Indiana totaling more than 10 inches of rain.  Through July 17 Kokomo, IN has received 15.76 inches of rain, and Young America 14.69 inches.  The flooding caused by the rain has caused an estimated 5 percent loss corn and soybean crops in Indiana, and 40 counties have received federal disaster declarations. Temperatures during the week averaged one to three degrees below normal (Figure 4), with southwestern Missouri being the only area slightly above normal

Developing low pressure in the Dakotas on July 14 triggered a line of thunderstorms that rolled through Minnesota southwestward into Iowa during the afternoon and evening. Tornado watches were in effect for much of Minnesota and Iowa. Severe weather was reported throughout Minnesota (Figure 5), with 1.00 to 1.25 inch hail reported in a number of locations.  At least four tornadoes were sighted in the southern part of the state.  An F2 tornado caused extensive damage near St. Clair, MN. Another F2, two F1, and one F0 tornadoes were confirmed by the National Weather Service.  This squall line continued east during the night, and during the early morning hours of July 15 it plowed through Illinois and Indiana (Figure 6).  The storms knocked out power to 52,000 ComEd customers in Chicago area.  Non-thunderstorm wind gusts of 50-60 mph developed in the early morning hours in eastern Iowa and western Illinois as rapid pressure falls producing a strong pressure gradient ahead of a developing line of storms.

The weather was relatively quiet across the Midwest on July 16.  Thunderstorms erupted across central and northern Missouri during the early morning hours of July 17 (Figure 7), dropping a much needed 0.50 to 1.00 inch of rain.