Some 33 million people are under winter storm watches and 27 million others are under wind chill alerts ahead of an Arctic outbreak and a related major storm sweeping the country this week.
Threat level: Arctic air began to bite across the Northern Plains Monday, ahead of the blockbuster storm forming and hammering the Midwest and the Great Lakes later this week. Forecasters are warning of power outages and "extensive" holiday travel delays throughout the Midwest and East.
