Midwest Weekly Highlights - September 8-14, 2005

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Wild Weather in Parts of the Western Midwest

The dominate high pressure ridge over the Midwest shifted eastward during the week of September 7-14, allowing upper level southwesterly flow over the western Midwest at times. Severe weather outbreaks occurred through Minnesota / Iowa / Illinois on the 8th, Minnesota on the 12th, and Wisconsin / Illinois / Michigan and Missouri / Iowa on the 13th. Some portion of Minnesota was subject to heavy rains on 5 days of this week, leaving large areas within and adjacent to the state with 2-4 inches of rain for the week (Figure 1). The precipitation total exceeded 200% of normal over most of this area, and only parts of southern Missouri were as rainy. Most the Ohio Valley received less than 25% of normal precipitation (Figure 2). Because of the dominate ridge and southwesterly flow, temperatures were above normal throughout the Midwest. While the western Midwest was only 4-7°F above normal where the rain fell, the central Midwest and Great Lakes were 7-12°F above normal for the week (Figure 3), setting daily temperature records in a few places and rapidly drying in areas that missed recent rains. The combined heat and lack of precipitation caused drought to intensify once again in and around the core drought areas in Illinois through the morning of September 13 (Figure 4, National Drought Mitigation Center). Western parts of the extreme drought area did receive some beneficial rains between the 13th and 14th, but not enough yet to change the long-term drought status.

Severe Weather Rakes Iowa

A strong squall line traveled across Iowa from 9 AM to 3 PM on September 8. Wind reports above 60 mph were common all the way across Iowa (Figure 5, Storm Prediction Center - SPC), along with some tremendous hail early in the storm life cycle. In Everly, IA (just west of Spencer in Figure 6, National Weather Service - NWS), large amounts of hail fell prior to 10 AM, leaving 1-2 ft drifts and blocking the main road through town for most of the day. Some stones were reported to be the size of baseballs, and, combined with 70 mph winds, caused damage to 26 houses and even destroying some garages. Wind and hail also caused power outages and pounded crops along the storm path.

Further west, a small tornado touched down in Ames, Iowa, at Iowa State University (about 30 minutes before the radar shown in (Figure 7, NWS). Eight people were injured, and one required hospitalization. A peak wind gust of 83 mph was recorded in Ames. At least $100K in damage occurred to buildings and grounds on campus. The storms exited Iowa around 3 PM and continued southeastward all the way to central Illinois and near St. Louis (Figure 8, NWS). Even in Illinois, a tornado was spotted in Mount Sterling, and several other severe events were reported before the storms finally dissipated.