CEDAR RAPIDS, Iowa (KCRG) - UPDATE 10:04 p.m.: The Tornado Watch expired at 10 p.m. The threat for severe weather is less as the night goes on.
Tornado Watch #639, in effect until 10:00 p.m. on Monday, September 9, 2019 (KCRG)
The threat for some severe thunderstorms which could contain tornadoes exists this evening, according to forecasters, and clusters of storms have produced reports of wind damage.
The Storm Prediction Center in Norman, Oklahoma, has issued Tornado Watch #639, effective until 10:00 p.m. for the counties shaded in yellow on the map in this article. In the KCRG-TV9 viewing area, this includes Allamakee, Benton, Black Hawk, Bremer, Buchanan, Butler, Chickasaw, Clayton, Delaware, Dubuque, Fayette, Floyd, Franklin, Grundy, Hardin, Howard, Iowa, Johnson, Jones, Linn, Marshall, Poweshiek, Tama, and Winneshiek counties.
Storms are expected to develop in central Iowa and lift to the northeast. Due to favorable amounts of energy in the atmosphere and wind shear, or the change in speed in direction of winds as height increases in the atmosphere, severe storms will be possible. Large hail, damaging winds, and tornadoes will be possible.
"A warm front that is lifting north across the area will be the area to watch tonight," TV9 Chief Meteorologist Joe Winters said. "The area near that front would have the highest potential for a storm that could produce a tornado. Fortunately, the window for it to occur will be relatively narrow, with the earlier sunset times being to our benefit as far as severe storm chances."
More thunderstorms are possible this week, with the next best chance coming on Thursday as a cold front moves across the viewing area.