Update 7:01 p.m. Wednesday, May 11:

The National Weather Service in Des Moines extended the Tornado Watch until 9 p.m. for 19 of the counties, including Story and Polk counties.

The Daily will continue monitoring the situation and post additional updates as they become available.

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The National Storm Prediction Center in Norman, Okla. issued a Tornado Watch for 39 of Iowa’s 99 counties, including Boone, Story and Polk counties, Wednesday afternoon. The watch remains in effect until 7 p.m.

The National Weather Service’s Hazardous Weather Outlook calls for scattered thunderstorms throughout the day and overnight. It indicates that some storms could be severe with “large hail and damaging winds being the main threat.”

A Tornado Watch is issued when conditions are favorable for the development of tornadoes. The National Weather Service issues them well in advance of actual severe weather, according to a posting on its website.

Information about the university’s tornado procedures are available on the Department of Environmental Health and Safety’s website.

The Iowa State Daily will continue to watch for updates from the National Weather Service and will post new information as it becomes available. Information will also be available on our Facebook and Twitter pages.