July 18-24, 2011
Midwest Weekly Highlights - July 18-24, 2011
Turning Up the Heat
An upper level ridge of high pressure established itself over the central U.S. this week, and the result was widespread heat and humidity across the eastern two-thirds of the nation. Average daily temperatures across the Midwest this week ranged from 5°F to 10°F above normal, with the greatest departures in a band from western and northern Missouri eastward across Illinois, Indiana, and into western Ohio (Figure 1). Average daily minimum temperatures, in particular, were much above normal, ranging from 8°F to 12°F above normal across most of the region (Figure 2). The high daytime temperatures, high dewpoints in the mid 70s to low 80s, and high minimum temperatures all combined to produce an extended heat wave this week. Excessive Heat Warnings were in effect for all or portions of the nine Midwestern states most of the week as heat indices rose to as high as 118°F. Outside of the warning area Heat Advisories were in effect (Figure 3).
The very humid air did help to keep maximum temperatures below records in many locations, but also served to keep overnight temperatures in the 70s to low 80s. High minimum temperature records far outnumbered the high maximum temperature records this week. There were 994 record high minimum temperatures set or tied this week, compared to only 318 record high maximum temperatures. Akeny, IA (Polk County) had three consecutive days of record highs above 100°F, with 104°F on July 19th, 105°F on July 20th, and 103°F on July 21st. Temperatures over 100°F also reached into southern Wisconsin and Michigan on July 21st (Figure 4). Fort Atkinson, WI (Jefferson County) set a new daily record of 103°F on July 21st, and a new record of 100°F was set in Detroit, MI.
There have been a number of deaths in the Midwest as a result of the heat wave. An estimated 20 people succumbed to the heat in Illinois, with 15 of those in the Chicago area. Officials in Wisconsin report three deaths due to the heat, and an there have been estimated 17 heat-related deaths so far this summer in Kansas City.
The heat also had impacts on agriculture. The corn crop was beginning pollination in many areas during the week, and the heat, lack of rain, and high overnight temperatures were stressing the crop. The Iowa Cattlemen’s Association estimated that up to 4,000 head of cattle died this week because of the heat, the majority of those in eastern Iowa.
Storms Bring Localized Relief from Heat, Flooding, and Damage
Severe thunderstorms were reported throughout the region this week, with the greatest concentration of storms on the periphery of the upper level ridge (Figure 5). Precipitation this week was concentrated across Minnesota, Wisconsin, northern Illinois, Ohio, and eastern Kentucky (Figure 6). Early in the week heavy rain fell in Wisconsin and in northern Ohio, causing widespread flash flooding. Communities in northern Ohio were particularly hard hit. 4.84 inches of rain were recorded at the Akron-Canton Airport (Summit County) on the morning of July 19th. The heavy rain closed roads and shut down the airport for several hours when six feet of water flooded the terminal building basement. Severe weather was also reported, with winds gusts to 73 mph. Summit and Stark Counties suffered the worst of the damage from these storms. Summit County officials declared a state of emergency on July 20th because flood waters were not receding, and 400 Akron residents reported flooding in their homes. 43,000 customers of FirstEnergy Corp. lost power, most from a flooded substation.
A weak push of cooler and drier air brought relief to the upper Midwest on July 22nd, but then stalled out across central Iowa, northern Illinois, northern Indiana, and northern Ohio on July 23rd (Figure 7). This boundary, combined with the very warm and humid air mass to the south, set the stage for a major heavy rain event. Thunderstorms on July 22nd into the morning of July 23rd produced three to five inches of rain across northern Illinois (Figure 8), with an excess of seven inches of rain in northern Cook County (Figure 9). 6.86 inches of rain was recorded at O'Hare International Airport, establishing July 23rd as the wettest calendar day on record for Chicago. The storms also were accompanied by damaging winds, and ComEd reported that 87,000 customers lost power due to the storms. The heavy rain resulted in many flooded roads and basements. Major flooding resulted on the Des Plaines River which flows through the northwest suburbs.
Severe storms along the front also pounded northern Ohio for a second time this week. Severe storms with intense lighting, high winds, and heavy rain toppled trees and power lines in the Cleveland area (Cuyahoga County), One fatality was reported when trees and power lines fell on a car, killing the driver. In Ottawa, OH (Putnam County) winds from a thunderstorm knocked over most sections of a 10,000 pound, 288-foot long granite Vietnam Veterans Memorial Wall being displayed for a weekend festival.
On July 24th severe storms moved through southern Ohio, knocking out power for 14,000 customers in the Dayton (Montgomery County) area and bringing a premature end to a major air show.
MIssouri River Flooding Update
Moderate to minor flooding continued along the Missouri River this week from Brownville in northwest Missouri to St. Charles in eastern Missouri. Wednesday, July 20th marked a record 50th consecutive day that the river has been above flood stage in Council Bluffs, IA (Pottawattamie County).
-SDH-