OMAHA, Neb.—One person died in Iowa as a powerful storm system swept across the Great Plains and Midwest amid unseasonably warm temperatures, bringing hurricane-force wind gusts and spawning reported tornadoes in Nebraska, Iowa, and Minnesota in a weather outbreak experts described as extremely unusual for December. The storm was shifting north of the Great Lakes into Canada on Thursday, with high winds, snow, and hazardous conditions continuing in the upper Great Lakes region, the National Weather Service said. More than 400,000 homes and businesses were without electricity Thursday morning in Michigan, Wisconsin, Iowa, and Kansas, according to poweroutage.us, which tracks utility reports. A tornado was reported in southern Minnesota on Wednesday and, if confirmed, would be the state’s first ever in December. The small community of Hartland, Minnesota, might have been the hardest hit, with a reported 35 to 40 homes sustaining minor damage while a few businesses were severely …