The Storm Prediction Center has issued a Severe Thunderstorm Watch effective until 4am for the following counties, Adair, Adams, Appanoose, Audubon, Boone, Carroll, Cass, Clarke, Crawwford, Dallas, Davis, Decatur, Fremont, Greene, Guthrie, Harrison, Jasper, Lucas, Madison, Mahaska, Marion, Marshall, Mills, Monroe, Montgomery, Page, Polk, Pottawattamie, Poweshiek, Ringgold, Shelby, Story, Tama, Taylor, Union, Van Buren, Wapello, Warren and Wayne. Thunderstorms continue to develop and move across the state. The main threats will be from large hail up to golf ball size and winds up to 60mph. A secondary threat will be from heavy rainfall that could cause some flash flooding as well.