Snow accumulations in the advisory area are expected to reach four inches at most, Mr. Staarmann said, and roads may become slippery. For Sunday, he projected a slight chance of snow showers, but “nothing significant.”

For areas around Boston, snow was expected to start Saturday afternoon and gradually turn to rain, Bill Simpson, a meteorologist for the National Weather Service in Norton, Mass., said on Saturday.

A winter storm warning is in effect for north-central Massachusetts and much of the western portion of the state from 2 p.m. Saturday through 7 a.m. Sunday, the agency said. Heavy snow is expected, with accumulations from four to eight inches.

Travel conditions will deteriorate once the snow starts, Mr. Simpson said. “It’s quick moving, so it will pretty much be over by daybreak.”

While snow gripped large expanses of the United States, it prompted a rare state of emergency in St. John’s, the capital of the Canadian province of Newfoundland and Labrador, where 30 inches of snow fell at the airport on Friday, smashing the previous record for snowfall in a single day. That record was set in 1999, when 26.9 inches fell at the airport in a single day. The city ordered businesses to close and banned cars other than emergency vehicles from local streets.

Videos posted on social media showed a snowboarder barreling down a steep city street, a man opening his garage door to find it almost completely blocked by a snowdrift and cars entombed in white.

The mayor of St. John’s, Danny Breen, said he had not been able to get his car out of his driveway, which was blocked by a six-foot snowbank.