July 11-17, 2011
Midwest Weekly Highlights - July 11-17, 2011
Heat Mostly Stays at Bay
While the far southwestern portion of the region did have to cope with much warmer than normal temperatures, most of the region had typical summer weather this week. Temperatures across Minnesota, in fact, were near normal and about 1F to 2F above normal across Wisconsin and Michigan (Figure 1). Temperatures were also near normal across southern Ohio and eastern Kentucky. Western and southwestern Missouri felt the brunt of the heat this week with temperatures averaging 5F to 7F above normal. Afternoon high temperatures were well into the 90s, and often accompanied by dew points in the mid to upper 70s (Figure 2). Temperatures in southwestern Missouri topped 100F July 11th and July 12th (Figure 3), but then cooled off into the 80s to low 90s the rest of the week. There were numerous temperature records this week, largely record high minimum temperatures. Surprisingly, scattered locations, mostly in Kentucky and Ohio, record low and record low maximum temperatures during the first half of the week.
A Mix of Wet and Dry
Most of the Midwest received much below normal rainfall for the week with one notable exception. Rainfall over the southern half of Minnesota, western Wisconsin, and northern Iowa was more than twice normal, reaching 500 percent of normal in south central Minnesota (Figure 4). A portion of southern Illinois and eastern Kentucky also received above normal rainfall this week, Elsewhere, rainfall was spotty. Through this week the driest portion of the region for July extends from eastern Iowa across northern Illinois into central Indiana with less than 50 percent of normal rainfall. The July 12th Drought Monitor indicated abnormal dryness only across Missouri (Figure 5), but that is likely to be expanded into the aforementioned areas in the next week without substantial rain.
Thunderstorms Roll Across the Midwest
Although the rain was hit and miss in many locations, there were several significant thunderstorm events that produced substantial rain and/or severe weather (Figure 6). The first and most significant of these was on July 11th. A derecho moved across northern Illinois, southern Wisconsin, and southern Michigan. Thunderstorms generating straight-line winds in excess of 70 mph raced across this area, causing widespread damage (Figure 7). The storms hit during the morning rush hour, disrupting commuter trains and travel on roads in the metropolitan area due to the numerous downed trees and power lines. O'Hare and Midway airports were shut down for close to an hour, Commonwealth Edison reported that 852,000 customers throughout northern Illinois were affected, the worst storm since 1998. 463,000 customers were still without power on the evening of July 11th, and it was another four days before power had been restored to all customers. The derecho also caused a seiche on Lake Michigan. City of Chicago officials were working to prevent heat-related illnesses as many residents were without air conditioning due to the power outages. Fortunately, a cold front moved through northern Illinois on July 13th lowering temperatures and humidity. Farmers in northern Illinois reported significant lodging of the corn from the winds. In southern Wisconsin, Monroe County was hard hit. Roofs were ripped off houses and businesses, and several semi trailers were overturned.
Severe storms in Kansas City, MO on July 12th left 30,000 residents without power. Kansas City Power & Light distributed dry ice to residents to help with refrigeration of food.
Thunderstorms with torrential rains moved through southern Minnesota and northern Iowa on July 15th, prompting flash flood warnings for a number of counties. More than three inches of rain fell from the Twin Cities south into northern Iowa (Figure 8). Four to almost six inches of rain were recorded by CoCoRaHS observers in southern Anoka and Ramsey Counties in Minnesota (Figure 9). Dozens of cars were totaled in Minneapolis-St.Paul because of flooding, and part of Interstate 35W was still closed on the morning of July 16th due to water on the road.
Missouri River Flooding
The Missouri River in Iowa and Missouri remained at Moderate to Major flood stage at most gauging stations. Kansas City residents reported that mosquitoes were an increasing nuisance because of the high flood waters, forcing many to stay indoors. While the flood plain mosquitoes are a nuisance, they are not a health threat.
The flooding has caused significant delays and problems for Amtrak over the last six weeks. The Empire Builder, which runs from Chicago to the Pacific Northwest, has only been able to travel as far west as Minneapolis. More than 1,000 miles of track has been closed between Minneapolis and north central Montana. The route resumed full service on July 17th after more than a month of disruptions. The California Zephyr, which runs from Chicago to San Francisco, has had to be routed around Omaha. Travelers stopping in Omaha board a bus in Lincoln, NE for the final leg to Omaha. The Missouri River flooding has affected Amtrak routes in Missouri, Iowa, Minnesota, Nebraska, North Dakota, and Montana.
-SDH-