Midwest Weekly Highlights - August 18-24, 2010

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Temperatures Slightly Warmer Than Normal

Midwest temperatures ranged from around normal to a few degrees above normal in the third week of August. Maximum temperatures (Figure 1) were in the low 70s in northern Michigan and in the mid 90s in southwest Missouri. Minimum temperatures (Figure 2) were in the 50s and 60s across the region. Departures from normal (Figure 3) ranged up to 4° to 5°F above normal in southern Missouri, eastern Ohio, and from the Iowa-Minnesota border eastward into Lower Michigan. Daily temperature records were limited to a few dozen for the week.
 

Precipitation Varies

Precipitation, shown as a percentage of normal, varied across the region (Figure 4). Two swaths, one from southwest Minnesota to northern Lower Michigan and the other from western Iowa to southern Kentucky, showed above normal precipitation totals. Very dry conditions were reported from southeast Minnesota and northeast Iowa eastward and southeastward to include the southern two-thirds of both Wisconsin and Lower Michigan, northern Illinois, Indiana, northern Kentucky, and most of Ohio. Northwest Minnesota and southwest Missouri were also dry. Nearly 200 daily precipitation records were set, some of which were also all-time or monthly records as well.
 

Midwest Drought

In the upper Midwest, drought conditions (Figure 5) eased slightly as heavy rains helped to restore streamflows and lake levels. To the south however, drought conditions expanded and worsened as agricultural impacts mounted due to hot, dry conditions.
 

Flooding Eases

The persistent flooding in Iowa eased during the week with most gauges falling below flood stage. A few locations on the Des Moines River and the South Skunk River in southeast Iowa (Figure 6) and (Figure 7) and further south along the Mississippi River (Figure 8) remained above flood stage. A brief, but intense, downpour in Ottumwa, Iowa (Wapello County) of more than 4" briefly pushed the Des Moines River levels up on the 20th, but then the falling river levels quickly resumed (Figure 9).
 

Severe Weather

Despite the quiet week for severe weather, there were tornadoes, large hail, and damaging winds mostly on the 19th and 20th. Two tornadoes touched down in Michigan (Macomb County) and one in Wisconsin (Brown County) and a possible tornado was reported near Linn, Missouri (Osage County). Hail, 1" or greater, was reported in Minnesota (Wilkin County), Wisconsin (Rusk, Price, Iron, and Brown Counties), and Michigan (Saginaw, Macomb, Schoolcraft, and Alger Counties). Damaging winds were reported in Minnesota and Michigan on the 19th (Figure 10) and from Missouri to Wisconsin on the 20th (Figure 11). More than 80,000 lost power in southeast Michigan (Macomb and Oakland Counties) on the 19th. In Wisconsin on the 20th, 20,000+ lost power with the outages spread across several counties (Washington, Jefferson, Dodge, and Brown Counties).
 

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