Midwest Weekly Highlights - August 11-17, 2014

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Pockets of Above and Below Normal Precipitation

Precipitation in the Midwest during the second week of August ranged from some areas experiencing significantly above normal precipitation to others experiencing significantly below normal precipitation (Figure 1). Areas with precipitation ranging from 200% to 500% of normal include eastern Michigan, much of Ohio, a swath from southern Iowa through western Kentucky/Indiana, central Minnesota and northeast Wisconsin. On the other hand, a large area including southeast Minnesota, southern Wisconsin, northern Iowa, northwest Illinois received 0% to 25% of normal precipitation. Southern Missouri and northern Minnesota also experienced significantly below normal precipitation.

Weekly precipitation totals ranged from 0" in portions of Iowa and northern Minnesota to 3" to 4" in southern Iowa, northern Missouri, and northeast Michigan (Figure 2). The precipitation patterns this spring and summer has resulted in a fairly drought-free Midwest. Currently, only 2% of the region is experiencing Moderate Drought (D1), while an additional 10% is abnormally dry (Figure 3).

Below Normal Temperatures Continue

Below normal temperatures continued throughout the second week of August in the Midwest, with temperatures anywhere from -1°F to -8°F below normal (Figure 4). Upper Michigan experienced the greatest departures of -6°F to -8°F below normal. On the coolest days during the week, minimum temperatures dipped down to 35°F to 40°F in northern Wisconsin and Upper Michigan (Figure 5). The only areas that experienced near or above normal temperatures during the week were in Minnesota. Temperatures were slightly above normal in northwest Minnesota, but only by +1°F to 3°F.

Widespread below normal temperatures have been the story this summer in the Midwest. June has been the only month to experience weeks where above normal temperatures dominated the region.
 

Minimal Severe Weather

Similar to last week, severe weather was minimal across the Midwest during the second week of August (Figure 6). The severe weather occurred in the eastern half of the region on August 11th and 12th, while the remaining tornado reports in Iowa came on August 17th. All reports were minor and produced minimal damage.

Flash Flooding in Detroit

On August 11th, 4" to 6" of rain fell on the Detroit Metro area in an 8 hour period, with the heaviest during rush hour which impacted up to 1,000 cars. The rain set up directly over the city center, so most of the rain fell on concrete and led to significant run off. The interstate system was greatly affected, with widespread roads flooding and some interstate ramps washed out. Embankments along many freeways were also washed away, leaving piles of mud on the road. The interstates in the area remained closed for several days as the water receded and debris was cleaned up. Crews were also forced to check the safety of area bridges after sinkholes opened up near roadways and powerful rain caused structural damage to some overpasses. The 4.57" that was recorded for the day at Detroit Airport was the second highest amount in 140 years of record keeping. The record is 4.74" from July 31, 1925. In addition, two hydro gages went to record stage during the event.

-MW-
Extension Climatologist for Illinois-Indiana Sea Grant and the Midwestern Regional Climate Center