Strong storms swept through the Pittsburgh area on Tuesday evening, prompting tornado and severe thunderstorm warnings. The storms left behind a trail of damage, knocking out power to tens of thousands of people.

ST. LOUIS — An elementary school south of St. Louis was damaged by a possible tornado as severe storms rolled through the region on Tuesday. The storm caused damage to Potosi Elementary School and left debris from a nearby building on the school’s parking lot.

Millions in the Upper Midwest face the possibility of a severe thunderstorm outbreak Monday—the start of several days of extreme weather threats across the country this week.

Both Minnesota and Wisconsin were hit by tornadoes during Monday night's severe storms, the National Weather Service confirmed.

Forecasters are warning that damaging winds, large hail, and even tornadoes could hammer the upper Midwest on Monday.

Monday had most of the ingredients needed for severe weather in southern Minnesota, but the absence of certain conditions kept it from becoming the worst-case scenario. Heavy rain, small hail and