On May 11, 2000, severe thunderstorms produced large hail and at least seven tornadoes across northeastern Iowa including one that killed one person and injured 25 others as it produced F3 damage near Dunkerton, Iowa. This would be affecting some of the same areas that would be struck by the EF5 Parkersburg tornado eight years later. The largest reported hail stones were the size of baseballs, falling near Dorchester in Allamakee County.
You can find more information regarding this event from the following sources:
http://www.silverliningtours.com/may-11th-2000-dunkerton-iowa-f3-tornado/
http://cbs2iowa.com/news/local/15-years-since-dunkerton-tornado