July 1-10, 2011
Midwest Weekly Highlights - July 1-10, 2011
A Warm, Dry Start to July
A ridge of high pressure aloft spread across the southern half of the United States was the dominant weather feature for the first ten days of July (Figure 1). This brought typically warm and at times humid weather to the region. Several weak cold fronts pushed into the central Midwest during the period providing some relief from the humid weather and triggering occasional showers and thunderstorms.
Temperatures across the region were above normal this period (Figure 2). Temperatures were near to sightly above normal from wesern Iowa east-southeastward to Kentucky, but were 4°F to 5°F above normal in southwestern Missouri as well as in eastern Minnesota and western Wisconsin. Numerous record high maximum and minimum temperatures were set during the first few days of the month, and then again on July 10th as the heat became reestablished across the region.
Rainfall was below normal across most of the region, with less than five percent of normal rainfall in eastern Iowa and northwestern Illinois (Figure 3). Rainfall was heaviest in western Minnesota and from southern Missouri across southern Illinois, where the frontal systems tended to stall out. There is no drought currently depicted for the Midwest, although the July 5th U.S. Drought Monitor shows increasing dryness in southern Missouri, on the fringes of the southern Plains drought (Figure 4).
Severe Weather
There were reports of severe weather in all nine states this period (Figure 5), but most of the the severe weather was concentrated in two periods. A strong cold front moving through the Midwest on July 1-2 resulted in widespread severe storms across central and southwestern Minnesota and northwestern Wisconsin on July 1st (Figure 6) and central Iowa on July 2nd. Wind damage was widespread in Minnesota on July 1st, with wind estimates to 95 mph. Three EF-1 and one EF-0 tornadoes were confirmed by the National Weather Service office in Chanhassen, MN. An EF-2 tornado was confirmed in Douglas County, WI, destroying one house. Hail 4.25 inches in diameter was reported in Meeker County, MN, and hail stones 3.5 inches in diameter occurred in Pine County, MN. The widespread damage from the storms led Minnesota Mark Dayton to declare a state of emergency for 16 Minnesota counties (Figure 7).
The second significant severe weather period was on July 10 when storms erupted ahead of a weak cold front across Minnesota, central Iowa, and Wisconsin (Figure 8). There were multiple reports of a tornado near Grove City, MN (Kandiyohi County) and many reports of damaging winds.
Missouri River Flooding
Moderate to major flooding continued on the Missouri River from Kansas City to Columbia, MO. The flooding forced Amtrak to temporarily suspend train service between Kansas City and St. Louis. Officials were also watching a section of levee in western Missouri that had sloughed off into the river. In Watson, MO (Atchison County) additional flooding resulted from a levee that was more seriously damaged following a breach two weeks ago. In Iowa, an agriculture disaster declaration was approved for the counties of Fremont, Harrison, Mills, Monona, Pottawattamie, and Watson (Figure 9), and surrounding counties were named part of the contiguous disaster area allowing farmers to be considered for assistance. Many roads in Iowa and Missouri remain closed due to the flooding. The Iowa Department of Transportation awarded a contract of $1.18 million to add a foot of asphalt to elevate a 4,200 foot section of Interstate 29 in Monona County to prevent inundation of the road. High reservoir releases along the upper Missouri River by the Army Corps of Engineers are planned to continue through August.
-SDH-