Flash Flood in Iowa, June 22 to 23, 1997

Continuing from what occurred during the afternoon, thunderstorms expanded over northern Iowa. What occurred as the storms over the north central counties drifted north was a merger of two areas. Intense thunderstorms formed over southwest Minnesota and eastern South Dakota during the afternoon. These storms moved southeast, while the storms from Iowa moved north. When the two merged over south central Minnesota, a mesoscale vorticity maximum was formed. The storms then all drifted south into Iowa. Initially, the storms produced very large hail. Hail up to three and one half inches in diameter fell in and around Forests City in Winnebago County. Windows and mirrors were smashed on two to three dozen cars at the 3M packaging plant there. Paint was also stripped off of some of the cars. There were two cases in the Westgate Addition, also in Forest City, where hail went through the sceens, two thermopane windows, and the venetian blinds...then landed on the on the floor. In one case, the hailstone landed 7 feet away from the window inside the house, on a bed. Later reports from Forest City indicate that 450 roofs in the area were damaged to the point that they needed to be replaced. The storm that produced the large hail produced a VIL value of 96 Kg/m/m on the WSR-88D display. Hail was widespread from the storms, however there was not much in the way of wind reported. Considerable damage was done to crops in the area, though it will be harvest time before the extent of the damage is totally known. The storms also produced copious amounts of rainfall. In Butler County, three and one half inches of rain fell in 30 minutes from one of the storms. Flash flooding became a problem in a four county area extending from west of Mason City to west of Waterloo. The most widespread flash flooding was over central Franklin into southern Butler County. County officials reported water over many county roads with considerable debris over roadways. Thousands of acres of cropland were flooded.