Midwest Weekly Highlights - September 17-23, 2011

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A Quiet Week

The third week of September was uneventful across the Midwest with cool, dry fall weather for much of the region.

A series of cold front passing through the Midwest reinforced cool air over the region. Temperatures this week were near normal from Indiana eastward, and from 1°F to 4°F below normal from Illinois westward (Figure 1). The largest departures were found in western Iowa and southern Missouri. The coldest period was the first two days of the period, and record minimum and record low maximum temperatures were set in the western and northern portions of the region. The were only a small handful of records set from September 19-23.

The cold fronts that moved through the region this week tended to stall out along the Ohio River, and provided a focus for the rain that fell this week. Rainfall was 200 to 300 percent of normal from southwestern Missouri through the southern two-thirds of Indiana and into eastern Ohio (Figure 2). Rainfall was also well above normal in extreme northwestern Minnesota. Rainfall was less than 50 percent of normal across eastern Iowa, northern Missouri, western, Iowa, and southern Minnesota. As of September 20th Extreme Drought was still present from eastern Iowa through central Illinois and into southwestern Indiana (Figure 3). However, rain that fell in the latter part of this period will likely alleviate some of the dryness over southwestern Missouri and southern Indiana. More rain was expected over the Midwest as a strong upper level low become established over the Great Lakes on September 23rd (Figure 4).

The lone severe weather report in the Midwest this week occurred in southwestern Missouri, where thunderstorm winds toppled trees in Barry County, MO.
 

Strong Winds in Minnesota

A strong surface low pressure system and accompanying cold front crossed through Minnesota on September 20-21 and produced very strong winds. Winds gusts over 30 mph were common, and a gust to 50 mph was recorded in Canby, MN (Yellow Medicine County).
 

Troubles on the Mississippi River

After major flooding in the spring and again in the summer, the upper Mississippi River has receded to low water levels. On September 18th the river was shut to commercial traffic after barges hit bottom south of the Quad Cities. The U.S. Army Corps of Engineers assigned two dredges to clear sandbars and to reopen the channel.

-SDH-