(Reuters) – A winter storm swept across much of the U.S. Midwest and East Coast on Wednesday, hampering air travel and prompting officials to close federal offices in Washington and several large public school systems.

The National Weather Service warned the storm could make travel very difficult, with snow, sleet and freezing rain potentially causing downed branches and power outages.

The storm reached from northern Minnesota down through Missouri and east into the Mid-Atlantic region and could bring as much as 6 inches (15 cm) of snow along with sleet and freezing rain, the National Weather Service said in an advisory.

The storm forced the closing of federal agencies in Washington as well as schools in Philadelphia, Baltimore and Washington.

Hundreds of flights were delayed or canceled in and out of major airports in Washington, Philadelphia and Chicago, according to Flightaware.com. Airports told passengers on social media to check their airlines for delays and cancellations.

(Reporting by Brendan O’Brien in Milwaukee; Editing by Jeffrey Benkoe)