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.

Tuesday is a KDKA First Alert Weather Day with large hail 1.5"-2" in diameter (ping-pong and golf ball-size) possible along with damaging winds up to 75 mph at times.  Sunset Tonight: 8:14 p.m.Average High: 68 Low: 46First Alert: Tuesday due to enhanced risk (3 out of 5) for severe weather in the afternoon and evening.

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.