* WHAT...Flash flooding caused by excessive rainfall continues to be possible. * WHERE...Portions of central, north central, northeast, northwest, south central, southeast, southwest, and west central Iowa, including the following counties, in central Iowa, Boone, Dallas, Grundy, Hamilton, Hardin, Jasper, Marshall, Polk, Poweshiek, Story, Tama and Webster. In north central Iowa, Butler, Franklin, Humboldt and Wright. In northeast Iowa, Black Hawk and Bremer. In northwest Iowa, Pocahontas. In south central Iowa, Appanoose, Clarke, Decatur, Lucas, Madison, Mahaska, Marion, Monroe, Ringgold, Union, Warren and Wayne. In southeast Iowa, Davis and Wapello. In southwest Iowa, Adair, Adams, Cass and Taylor. In west central Iowa, Audubon, Calhoun, Carroll, Crawford, Greene, Guthrie and Sac. * WHEN...Through Saturday morning. * IMPACTS...Excessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations. Creeks and streams may rise out of their banks. Flooding may occur in poor drainage and urban areas. * ADDITIONAL DETAILS... - Several rounds of rain have brought 2 to 6 inches of rain to central Iowa this week. Additional rain this afternoon and evening will occur as storms push through. The combination of saturated soils and high rainfall rates may overwhelm capacity, which will increase flooding potential.