The Storm Prediction Center has issued a Severe Thunderstorm watch effective until 10pm for the following counties, Adair, Audubon, Black Hawk, Boone, Bremer, Butler, Calhoun, Carroll, Cass, Crawford, Dallas, Franklin, Greene, Grundy, Guthrie, Hamilton, Hardin, Humboldt, Jasper, Madison, Mahaska, Marion, Marshall, Pocahontas, Polk, Poweshiek, Sac, Story, Tama, Warren, Webster, Wright, Allamakee, Chickasaw, Clayton, Fayette, Floyd, Winneshiek, Benton, Buchanan, Cedar, Clinton, Delaware, Dubuque, Iowa, Jackson, Johnson, Jones and Linn. Thunderstorms are beginning to fire along the edge of last night and early this mornings storms that moved across the northern half of the state. Some of the storms will have the capability of producing large hail and damaging winds. Also an isolated tornado cannot be ruled out as well.