Washington ? A major storm moving up the Atlantic Coast on the last shopping weekend before Christmas threatened to shut down much of the region as officials warned of up to 20 inches of snow and significant power outages.

People stocked up on groceries and other staples Friday after the National Weather Service issued winter storm warnings from the Carolinas to Rhode Island.

In Virginia, Gov. Tim Kaine declared a state of emergency ahead of the storm, placing the National Guard and other agencies on standby. Philadelphia officials also declared a state of emergency and the school district canceled all weekend activities. Washington, D.C., declared a snow emergency.

The Federal Aviation Administration said departing flights at Hartsfield-Jackson Atlanta International Airport were delayed by as much as an hour Friday because of rain and wind. United Airlines said it had already canceled more than 140 flights on the East Coast ahead of today’s weather.

Forecasters expected up to 20 inches of snow through late today from the Washington metro area to West Virginia. They said it could be the most snow in the nation’s capital since a February 2003 storm dumped nearly 27 inches at Baltimore-Washington International Airport.