A winter storm that brought snow, sleet and freezing rain to a large swath of the Midwest swept into the mid-Atlantic and Northeast on Thursday, causing treacherous travel conditions, prompting school delays and closures and potential power outages for millions of Americans.

The National Weather Service says a mix of snow, sleet and freezing rain will continue to fall until Thursday evening.

Nearly half of the United States from the Midwest to Northeast will see snow or a freezing rain mix before the weekend arrives, weather forecasters say.