As millions of Americans hunker down for a massive winter storm sweeping the country, new maps are offering updated forecasts of snow and ice accumulations.

Heavy snow, sleet and freezing rain are slamming large parts of the U.S. as the dangerously cold weather causes major power outages and travel disruptions.

Severe to catastrophic ice accumulation is possible and could lead to prolonged power outages, worsen the impacts of the cold weather and create hazardous travel conditions.