WASHINGTON — With heavy snowfall predicted by the weekend from the Appalachians to Philadelphia and maybe farther north, people throughout the region readied themselves for blocked roads, power outages and canceled flights.

The National Weather Service said in a statement Wednesday that 12 to 16 inches of snow could come down between Friday night and Sunday morning around the Interstate 95 corridor. As much as a foot of snow is possible for Philadelphia’s northern suburbs.

Mitchell Gaines of the National Weather Service in Mount Holly, New Jersey, said people should be prepared for strong winds, heavy, wet snow and power outages.

The National Weather Service’s Weather Prediction Center warns of heavy, “perhaps crippling” snow across the northern mid-Atlantic region, including Baltimore, Washington and Philadelphia, probably beginning Friday.

In the District of Columbia, Mayor Muriel Bowser requested Humvees from the National Guard to reach isolated people and places if necessary.