Midwest Weekly Highlights - July 22-31, 2009
The pattern of cool July temperatures continued for the last ten days of the month (Figure 1). The entire Midwest was again below normal with departures ranging from 1°F in eastern Ohio to 5°F in Iowa and Missouri. Minimum temperatures were coolest (6°F below normal) in western Iowa (Figure 2) while the coolest maximum temperatures (6°F below normal) were along the northern and southern edges of the Midwest (Figure 3). The number of temperature records eased compared to the previous week, however there were still more than two hundred record lows posted in the final ten days of July.
Precipitation varied across the Midwest during the period (Figure 4). Rainfall exceeding 200% of covered Kentucky, most of Ohio, southern Indiana, and small parts of southeast Illinois and Missouri. Other areas receiving over 200% of normal were northeast Michigan, eastern Iowa, northwest Illinois, southwest Wisconsin, and small areas of northwest Minnesota. This period's drier areas extended from southwest Iowa to west central Minnesota and received less than 50% of normal rainfall. Near normal rainfall in northern Wisconsin did little to ease drought conditions as reflected in the US Drought Monitor product released July 28th (Figure 5).
July 23-25 Storms
A cold front moved south across the Midwest July 23-25 with thunderstorms ahead of the frontal boundary (Figure 6). The strongest storms occurred along a path from northwest Minnesota (July 23) to southwest Wisconsin and northwest Illinois (July 24) and then spread across extreme southern Indiana and eastern Kentucky (July 25).
July 23 reports indicated large hail fell in Polk County (2") and Marshall County (1.75") in Minnesota. Hail of at least an inch in diameter also fell in southeast Wisconsin, northeast Illinois, and numerous counties in northwest Minnesota. Thunderstorm winds in Randolph County, Illinois flattened corn and blew 40 rail cars over onto their sides.
July 24 had two swaths of storms move from southeast Minnesota into northwest Illinois. Tornadoes were reported in Lafayette County, Wisconsin and Bureau County, Illinois. As the storms moved south large hail was reported in numerous counties: 2" in Dodge County, Minnesota, 2" in Fayette County, Iowa, 2.50" in Delaware County, Iowa, 4.25" in Winneshiek County, Iowa, 2.50" in Jo Daviess County, Illinois, 2" in Stephenson County, Illinois and 2.75" in Lafayette County, Wisconsin. Reports from the USDA Farm Service Agency estimate 400,000 acres of crops were impacted by hail resulting in $200 million in damages in Iowa alone. Wind damage associated with these storms extended all the way into southern Indiana.
By July 25 the storm system was affecting extreme southern Indiana and eastern Kentucky. 1" hail fell in Magoffin County, Kentucky. Thunderstorm winds blew down trees and large limbs in Indiana and Kentucky. Later that night storms in southeast Missouri blew down large tree limbs (Pemiscot County). In neighboring Dunklin County, there were widespread power outages due to downed power lines and structural damage to homes.
July 27 Storms
After a quiet day on July 26, storms developed again on July 27 over southwest Wisconsin and northern Illinois. Tornadoes were reported in three Wisconsin counties (Marquette, Crawford, and Lafayette). In Crawford County, a barn roof was lifted off and crashed into the side of a hill. Hail up to 1" was reported in several Wisconsin counties and wind damage to trees was reported in both Wisconsin and Illinois. In Oregon, Illinois (Ogle County) a large limb fell onto a house causing minor damage.
Other Severe Weather
On July 22 hail 1" to 1.25" inches in diameter was reported in several Iowa counties and also in Polk County, Wisconsin. July 28 reports of hail in Illinois (1.5" Sangamon County), Indiana (1.5" La Porte County), and Ohio(1" Wood and Fulton counties) added to a few widely spaced reports of wind damage extending from Missouri to Ohio. Most of the wind damage was to trees except in Moniteau County, Missouri where siding was also blown off a home. Tornadoes were reported on July 30 in three states, Illinois (Boone County), Kentucky (Allen County), and Ohio (Wayne County). The Ohio tornado was responsible for significant structural damage to a barn near Wooster. July 31 saw large hail in western Minnesota and wind damage in northwest Iowa.