Damaging Wind in Iowa, August 8, 1994

Warm, humid, and very unstable air moved over Iowa during the afternoon of the 7th. A warm front moved northeast across the state during the day. During the late afternoon hours a cold front approached the northwest corner of the state. Very humid air was drawn north just ahead of the cold front. Dew point temperatures were in the lower to middle 70s over most of the state by evening. Northwest flow in the middle and upper levels brought in relatively cool air aloft over the area. As a result the lifted indices were in the -10 to -12. range. By early evening, convective available potential energy values reached 4000-6000 J-Kg-1 over much of the west half of Iowa. Thunderstorms fired in two areas initially. The first was over southern Minnesota. The second was over north central Nebraska. The two areas propagated south and grew toward each other with time. Though the storms were tornadic over Minnesota, the main severe weather event for Iowa was hail and high winds. The Minnesota convection dropped into north central and northeast Iowa. Dime-size hail was the result. There were sporadic reports of marble to dime-size hail for about 45 minutes over Winnebago County. Dime-size hail also fell over northwest Hancock County as the storms entered the Woden area. After this time, they weakened as they continued to move south-southeast. As the mesoscale convective system over Nebraska built into southeast South Dakota and northwest Iowa, high winds and hail resulted. Hail ranged in size from three quarter inch to golf ball in size. In Cherokee County, hail damage was reported to many cars in the city of Cherokee by hail 2 inches in diameter. Reports showed at least 150 cars and 100 homes were damaged by the hail. A tornado touched down northwest of Sibley, in Osceola County. One farmstead was hit with damage reported to several buildings, one was destroyed. A woman received minor injuries when she was cut on the hand by flying glass. Five hogs were killed when a concrete block building was collapsed. The building housed 300 hogs. A silo was destroyed on the farm and carried a mile to the south. At the same time one of the cars was lifted and thrown 50 feet. At about the same time, a farmhouse in rural Sibley was struck by lightning. The house was set on fire and was totally lost. Also in Osceola County, north of Sibley, a farmstead was hit by high winds in advance of the tornado. A concrete was destroyed and the end of the barn was completely removed. Woodbury and Monona Counties were hard hit by high winds. The first reports came from Danbury, where 60 to 65 MPH winds were reported. Numerous reports of trees and power lines being downed by high winds were received from Woodbury County. In Monona County, Mapleton and the area around it were hard hit. In the town of Mapleton, the roof was blown off of a car dealership, and the roof was caved in on one apartment building. In the downtown area, winds blew out a three quarter inch thick plate glass window. Several farmsteads were damaged by the winds as well. Two farms had significant structural damage. Another reported one grain bin blown off its foundation, and six others had the sides collapsed and bent over. Twelve hogs were killed when a quonset building was destroyed. One man was injured in Crawford County when high winds downed a large tree limb in front of the car that he was driving. The storms continued south, though they had weakened with winds around 50 MPH. Spotty damage occurred. High winds downed trees and limbs in Harrison County at Dunlap and Pottawattamie County at Council Bluffs. Several tents were blown down by the wind at the County Fair in Dunlap as well. There were also several lightning strikes. Lightning set a house on fire southwest of Sibley, destroying it. A barn was a total loss to fire northeast of Mapleton when lightning struck it. Another storm moved across Shelby County. Lightning struck two house in Harlan. Damage occurred to each, but actual dollar amount was not available.