The snow has been coming down hard for a few hours, and coupled with 40-plus mile an hour winds, area roads are "beyond treacherous," according to the State Highway Administration.
There are some vehicles moving on major highways, but in many cases, the roads are down to one lane and crews are having difficulty keeping those open, said David Buck, administration spokesman.
"This is a white-out, deteriorating condition," said Buck. "This is not a day to be outside."
Officials are encouraging people not to drive. Most governments, schools and businesses are closed, but essential workers have been heading out. There have been a smattering of crashes, Buck said, though no roads are yet officially closed.
Montgomery County and Washington have pulled snow crews off the roads, he said. For now, the state is leaving the decision to pull off the road to drivers, but in Baltimore, Mayor Stephanie C. Rawlings-Blake ordered Phase III of the snow plan to be instituted, meaning only city-authorized emergency vehicles were permitted on roads.
The snow got a slow start Wednesday morning, and Neil Pedersen, state highway administrator, said that gave crews a chance to plow and spread some salt. The state has about 180,000 tons and supplies have been shifted around to ensure that the Baltimore metro area, at the center of the storm, had enough.
The region is expecting 10-20 inches by this evening, according to weather forecasts.
"If people can stay home, we'd really like them to," Pedersen said.
There is no mail, trash or recycling pickup, flights from BWI Thurgood Marshall Airport are canceled and public transportation has become extremely limited.
The Maryland Transit Administration canceled local bus service as of 11 a.m., as well as above-ground subway service. Light rail is running on a limited schedule, though there is no connecting bus service.