Midwest Weekly Highlights - August 8-14, 2006

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Heat Backs Off, Rain Comes to Drought Areas

Temperatures this week moderated considerably from the previous week. Most of the region experienced temperatures at or below seasonal normals (Figure 1). Temperatures ranged from normal to 3°F below normal north of a line from Cincinnatti, OH to Des Moines, IA, and as much as 4°F below normal in northeastern lower Michigan. In contrast, the heat was tenacious in much of  Missouri, where temperatures averaged 5°F to 7°F above normal.

The coolest portions of the Midwest were also the driest this week. Rainfall was less than 25 percent of normal from northern Ohio northwestward to the Michigan UP (Figure 2). Rainfall was abundant from western Minnesota through Iowa, northern Missouri, the southern two-thirds of Illinois and into Kentucky, averaging 200 to 300 percent of normal for the week. The August 8 U.S Drought Monitor (Figure 3) continued to depict Extreme drought in the northern half of Minnesota, but there was some improvement in southern Minnesota and Iowa from the previous week. Further improvement is likely with this week's rain which will be reflected in the August 15th U.S. Drought Monitor. Rainfall for August through the first two weeks of the month has been well above normal from southern Minnesota south to northern Missouri, and near to above normal from there into Kentucky (Figure 4). This pattern reflects the southern extent of cold front passages in the Midwest the past two weeks.


Missouri Bakes

While most of the region enjoyed seasonable temperatures this week, Missouri residents continued to cope with temperatures in the mid to upper 90s and humid conditions. Although cooler and less humid air masses pushed through the Midwest during the week, the cool air often stopped short of making it through most of  the Show Me state. On August 9 high temperatures across central Missouri soared past the 100°F mark, reaching 103°F in Kansas City; 102°F in Joplin, tying the record set in 1980; 100°F in Vichy/Rolla, breaking the previous record of 99°F also set in 1980;  and 100°F in St. Louis (Figure 5).  By August 12 high pressure over the Great Lakes brought some relief from the heat, knocking temperatures back into the upper 80s and lower 90s.  On August 13, however, the heat was already creeping back into western and central Missouri as highs reached the upper 90s, and a high of 101°F occurred in Kansas City. Another cold front accompanied by showers and thunderstorms brought more substantial relief on August 14, when the high in Kansas City was only 82°F (Figure 6). The ongoing drought, combined with the extreme heat, has produced an extreme danger of wildfire in portions of central Missouri and a high danger in the Missouri Ozarks.


 Heavy Rain, Severe Weather

A number of areas in the Midwest were affected by heavy thunderstorms this week as a series of weather systems pushed through the region.

In Illinois, persistent training thunderstorms the morning of August 9 (Figure 7) dumped up to 7.50 inches of rain over Clay County in a four to six hour period. The observer five miles northwest of Flora reported 7.00 inches, the highest daily total since records began there in 1893. Other observers around Flora, IL reported from 7.00 to 7.50 inches of rain. The excessive rain pushed the Little Wabash River to crest almost four feet above flood stage causing flooding to adjacent farmland.

During the morning of August 10 a complex of severe thunderstorms moved from Iowa through northern Illinois. The storms produced some considerable wind damage in northern Illinois and northern Indiana. Later in the day, thunderstorms again developed across Iowa, northern Illinois, and southern Illinois and Kentucky. A tornado was reported in west-central Iowa, but there were no reports of significant damage. Heavy rain from these storms produced urban and street flooding throughout the Chicago metropolitan area. Torrential rains with the storms in western Kentucky also produced widespread flash flooding, with water reported as much as three feet deep over some roads.

There were scattered reports of severe weather on August 11 in Missouri and on August 13 in Missouri and Iowa. More severe weather occurred on August 14 from southern Missouri into southern Indiana and Kentucky ahead of the cold front pushing through the Midwest. Most of the reports were of damage caused by high winds, although there was a brief tornado touchdown in Carlisle County, KY.

SDH