Winter storm triggers nationwide disruption as states declare emergencies

A massive U.S. winter storm is causing widespread travel chaos, with more than 10,000 flights canceled across the weekend and tens of thousands more delayed; at least 17 states and Washington, D.C. have declared states of emergency and some National Guards have been activated as heavy snow, sleet, freezing rain and dangerous wind chills threaten about 200 million people. Widespread power outages are a concern, and authorities urge people to stay off the roads as airlines offer waivers and federal offices anticipate closures; the storm is expected to continue into Monday and bring frigid temperatures afterward.