Millions in the Upper Midwest are bracing for a severe thunderstorm outbreak that could unleash damaging winds, large hail, and strong tornadoes. This extreme weather event marks the beginning of several days of hazardous conditions across the United States. Here's a breakdown of the current situation and what lies ahead.

The upper Midwest is bracing for severe thunderstorms with the potential for strong tornadoes. The National Weather Service says the highest risks Monday are in portions of southern Minnesota, northern Iowa and western Wisconsin.