July 1-10, 2008
Midwest Weekly Highlights - July 1-10, 2008
More Heavy Rain in Central Midwest
The central portions of the region continued to deal with bouts of heavy rain the first ten days of the month. Rainfall from central Missouri eastward through Ohio was 150 percent to as much as 300 percent of normal, with the greatest departures in southern lower Michigan and in extreme southern Missouri (Figure 1). Heavy rain also fell across much of Kentucky where it has been dry. Precipitation in southern Kentucky has been running 60 to 75 percent of normal over the past 90 days, so the rain this week was helpful. Although thunderstorms occurred in Minnesota, rainfall for the start of July was well below normal. Less than 25 percent of normal rainfall for the first ten days of July fell from southwestern Minnesota into northeastern Minnesota and northwestern Wisconsin.
Temperatures across the Midwest ranged from well below normal to slightly above normal. The portions of the central al Midwest which received the heavy rain were also the coolest, with temperatures as much as 4°F below normal (Figure 2). The warmest areas in the upper Midwest were only near normal to 2°F above normal.
Nature's Fireworks
A cold front entered the northern Midwest on July 1 and progressed slowly to the central Midwest by July 3 (Figure 3). Low pressure developed along the front in the southern Plains and moved along the front, setting off thunderstorms from Missouri through Ohio. Late on July 2 two to six inches of rain fell in western Missouri northwest of Kansas City (Figure 4). The rain caused flash flooding in Parkville, MO (Platte County). The lower levels of 20 homes were flooded in one subdivision when debris blocked drainage tubes at a bridge. In central Missouri, three to four inches of rain fell in Moniteau, Cole, and Osage. Some of the storms were severe producing wind damage, and golf ball to baseball size hail was reported near Norborne, MO (Carroll County).
The storms continued on through the afternoon and evening of July 2 and the early morning hours of July 33 eastward through Ohio. The thunderstorms dumped three to six inches of rain in northwest Ohio and southeastern Michigan (Figure 5). Many roads were impassable due to high water, and a portion of I-475 in Toledo, OH (Lucas County) was closed during the morning rush hour on July 3. The storms knocked out power to more than 184,000 customers in Michigan and Ohio, and it was expected that some rural areas would not get power back until July 5.
Fortunately, high pressure building in behind the front brought cooler and less humid weather to much of the Midwest for the Fourth of July. The exception was along the Ohio River, where cloudiness and some rain lingered as the front slowed to a crawl as it entered Kentucky.
Next Round
The frontal boundary stalled south of the Ohio River began to return northward on July 6, and warmer, more humid air once again was streaming back into the Midwest. Another cold front dropping south out of Canada clashed with the unstable air mass and thunderstorms developed across the western Midwest. There were scattered severe storms, mostly in Iowa. Severe storms were numerous on July 7 in eastern Iowa, southeastern Minnesota, southern Wisconsin, and northern Illinois. A weak tornado touched down in Green Lake County, WI producing minor damage. These storms also produced more heavy rain across south-central Iowa. Two to more than four inches of rain accumulated in a 24-hour period (Figure 6) with the heaviest amounts of more than five inches inWarren County, IA (Figure 7). The severe weather and heavy shifted south into Missouri, central Illinois, Indiana, and Ohio on July 8.Reports of severe thunderstorm winds were most numerous in Ohio. Brief tornado touchdowns were reported in eastern Illinois and northeastern Indiana. In Hannibal, MO (Marion, Ralls Counties), three to four inches of rain was reported to fall in 40 minutes, causing creeks to overflow and flooding streets. Earlier in the day the city removed the flood gates from the riverfront area in the wake of the Mississippi Rover flooding.
...and One More
This period ended with severe storms concentrated in a small area from southeastern Minnesota into northern Illinois. The storms developed in response a a strengthening low pressure system in the Northern Plains. There were Numerous reports of damage from thunderstorm winds, and reports of EF0 to EF1 tornadoes in Minnesota, Iowa, and Wisconsin. Hail to 3.00 inches was reported near Winstead, MN (McLeod County), and 2.00 inch hail fell near Lake City, MN (Wabasha County) and Monticello, IA (Jones County). In Illinois, the severe storms knocked out power to 24,000 ComEd customers and caused delays up to 90 minutes at O'Hare International and Midway airports in Chicago.
Flooding Footnotes
The Mississippi River was opened to navigation on July 5 after 300 miles of the river was closed for almost a month due to record and near record flooding. While water levels have been dropping, river levels were still above flood stage in some areas. The river was still 7.1 feet above flood stage in St. Louis. The Kaskaskia Lock on the Kaskaskia River near Chester, IL (Randolph County) remained closed.
On July 7, the Iowa River at Iowa City (Johnson County) dropped below flood stage and was at 20.6 feet.
The record flooding in May and June shortened the Wabash River, the longest stretch of free-flowing river in the eastern United States. The floodwaters cut a new channel across a portion of Posey County, IN known as Mackey Bend. Authorities estimate that the river course has been shortened by at least six miles. The new channel created a new island which has cut off farmers in southwestern Indiana from between an estimated 1,700 to 2,700 acres of cropland, and left behind an oxbow.
SDH