EF1 tornado in Shelby County, Iowa

This tornado entered Shelby County from Pottawattamie County from the southwest. The tornado impacted a total of 6 farmsteads in the county as it tracked to the north northeast. Damage at these farmsteads was confined to mainly outbuilding being damaged or destroyed, trees uprooted, and electrical power poles downed. The tornado tracked across the western side of the Harlan Airport without doing damage to the airport, but a wind gust associated with the rear-flank downdraft of the storm was measured at 76 mph at the automatic observing equipment on the east side of the airport. The tornado finally ended just to the southeast of the city of Harlan.

A powerful upper level low pressure system moved quickly across the central Plains during the day on November 11th. As low pressure moved from Kansas into eastern Nebraska during the day, warm and moist air was pushed northward into the region. This unseasonably warm and moist air led to increasing instability during the afternoon over western Iowa and southeast Nebraska. This combined with the strong wind field associated with the low produced an atmosphere ripe for severe weather. Thunderstorms developed along the cold front in eastern Nebraska by early afternoon, and then increased in coverage and intensity as they tracked east into western Iowa during the early afternoon. Large hail and isolated tornadoes were produced by these thunderstorms.