Flash Flood and Flooding in Iowa, August 20, 1998

Iowa was covered by a very unstable and moist airmass. Precipitable water values were in excess of 2 inches with surface dew point temperatures in the mid 70s F. to the low 80s over all of the state. By afternoon, temperatures had risen into the low to mid 90s in most of the south two thirds of Iowa. This combination produced CAPE values in excess of 6000 J/Kg over the west half of Iowa. A cold front was located to the northwest of the state during the day. It sank southeast during the late afternoon and thunderstorms fired up in the rich environment ahead of the front. Initially, they moved quite slowly with a training line of thunderstorms developing over northern Iowa. During the late afternoon the storms dropped up to 2.2 inches of rainfall in an hours time over Butler and Bremer Counties. This caused some urban flooding in the area, however with soil conditions relatively dry major flooding did not occur. The situation was worse farther to the west. Very intense thunderstorms dropped 4 to 6 inches of rain on Hamilton County between Webster City and Williams. Four inches of rain fell in one hour in Webster City, with a total of 6.26 inches recorded there. Five inches fell in under two hours in Fort Dodge. Serious flash flooding occurred over the county in spite of the relatively dry conditions of the past few weeks. The town of Webster City was virtually under water for a time due to the intense rainfall rate, flooding most basements in the town. A freak lightning strike took place south of Carroll in Carroll County. Lightning struck a childs toy on a driveway there. The "Bigfoot" motorized power toy was completely destroyed by the strike. All that was left was a charred residue on the driveway. The younger daughter, about two years old, was pictured in the newspaper pointing at the charred remains and saying "Mommy, I don't want my Barbie car outside anymore."