September 15-21, 2010
Midwest Weekly Highlights - September 15-21, 2010
Cold North, Warm South
Two quasi-stationary frontal boundaries bisected the Midwest much of this week (Figure 1) resulting in a marked temperature contrast from north to south across the region (Figure 2). North of the mean position of the boundaries temperatures ranged from 1°F below normal across central Iowa into southern Michgian, to 5°F below normal in northern Minnesota. To the south of the boundary, temperatures ranged from 1°F above normal from northern Missouri across central Ohio to 7°F above normal in southwestern Missouri.
Maximum temperatures were 9°F to 11°F above normal in the Ohio River Valley, and 7°F to 8°F below normal in northern Minnesota (Figure 3). The mercury frequently soared to 90°F and above this week across the southern Midwest, with temperatures as high as 99°F in western Kentucky on September 21 (Figure 4).
Despite the marked and large contrast in temperatures, there were only a handful of temperature records set during most of the week, with record minimum and record low maximums in the north, and record high temperatures in the southern half of the region. On September 21, however, there were 40 record high temperatures set as unseasonably warm spread northward through the region.
Drought Expands in Ohio River Valley
With the stationary frontal boundary in the central Midwest and an upper level high pressure ridge nudging up from the south, significant rainfall was hard to find in the southerneastern Midwest this week. There was little to no measureable rain in extreme southeastern Illinois, southwestern Indiana, and western Kentucky (Figure 5). Rainfall was more than twice normal for the week from central Minnesota across northern Wisconsin, much of Iowa, and all but far southeastern Missouri. The heavy rain in Minnesota has caused harvest delays and unseasonably high river levels. In Otter Tail County high water has closed several county roads, and the persistent heavy rain forced construction projects to a halt. The September 21 U.S. Drought Monitor continuing improvement in Wisconsin, Minnesota, and Michigan, with severe drought only in the arrowhead of Minnesota (Figure 6). Dryness continued to worsen in the Ohio Valley, and severe drought was depicted this week in the Missouri bootheel and across southern Indiana and extreme southwestern Ohio.
Harvest Continues at A Good Pace
Corn and soybean harvest in the eastern half of the region continued well ahead of the 5-year average. Corn harvest was 37 percent ahead of the average in Kentucky, 26 percent ahead in Illinois, 22 percent ahead in Wisconsin, and 21 percent ahead of average in Indiana. In the wetter western portion of the region, corn harvest ranged from 4 percent ahead of average on Missouri to 1 percent behind in Minnesota. Soybean harvest ranged from 2 to 17 percent ahead of the 5-year average except in Minnesota, where it was 1 percent behind.
Severe Weather Pounds Ohio, Missouri
There was significant severe weather this week across the region, most of it concentrated along the mean frontal boundary position (Figure 7). The most damaging outbreak occurred on September 16, when 11 tornadoes touched down in central and southeastern Ohio (Figure 8). The storms developed as a cold front and strong upper level disturbance crossed the Midwest into Ohio. Thunderstorms began developing in the afternoon and continued into the evening hours. In Athens County, Ohio damage was extensive with 15 homes destroyed in Nelsonville. At least 200 people required temporary shelter and seven people were taken to the hoispital with injuries. One tornado crossed into West Virginia where one man died because of injuries from the storm. A total of at least 55 homes were destroyed in Athens, Perry, and Meigs counties
.
Another round of severe weather affected Iowa and Missouri on September 18 (Figure 9). The storms started on the afternoon of September 18 and continued into the early morning hours of September 19. The storms in Missouri produced extremely large hail, damaging winds, and heavy rain that caused flash flooding (Figure 10). A hail stone 5.5 inches in diameter was measured near Raytown, MO (Jackson County), and there were numerous reports of hail 2 inches or more in diameter. Hail reportedly fell for up to an hour at several locations along Interstate 70, causing extensive damage to vehicles. In southwestern Iowa, 1.75 to 2.50 inch hail was commonly reported, with one report of 3.00 inch hail near Cumberland, IA (Cass County).
Severe thunderstorm watches were posted from Iowa to lower Michigan on September 21 as unseasonably warm and humid air streamed northward and collided with the frontal boundary across the Midwest (Figure 11). Severe storms developed from eastern Iowa across northern Illinois into lower Michigan (Figure 12). There were numerous reports of hail 1 inch or larger. A wind gusts of 78 miles per hour reported in Roanoke, IL (Woodford County), and a gust of 75 mph near Muskegon, MI (Muskegon County). Several other locations in northern Illinois and Michgian reported winds gusts between 65 and 72 miles per hour. The storms knocked out power to over 100,000 customers in Michigan, and hail caused serious crop damage there.
-SDH-