Severe Weather Moves Across the South as the Northeast Braces for Heavy Rain

A storm system that battered parts of the South with heavy rain on Saturday was expected to reach the Northeast, bringing with it the potential for coastal flooding and powerful winds, forecasters said.

The city of Charleston, S.C., closed more than 20 roads in the downtown area as a result of heavy rain and high tides.

Some reports indicated that up to 3.5 inches of rain fell in the downtown area, said Marc Chenard, a forecaster with the Weather Prediction Center. An area near the waterfront reported getting nearly two inches of rainfall in an hour, he said.

In the Isle of Palms, a South Carolina city of 4,300 people that is about 15 miles east of Charleston, the police posted on social media urging residents to “not be driving right now if you do not absolutely need to be” as water levels continued to rise.

A tornado watch for portions of the Florida Panhandle as well as southeastern Georgia had been posted until 2 p.m., Mr. Chenard said. A few tornado warnings that were issued have since lapsed.

In Coffee County, Ga., high winds on Saturday damaged the roof of a mobile home and uprooted several trees, said Steve Carver, the Coffee County emergency management director and chief of the fire department. No injuries were reported.

The National Weather Service said that a subtropical jet stream, combined with moist air from the Gulf of Mexico, among other variables, would result in widespread severe weather across much of the eastern United States into Sunday.

Severe thunderstorms are possible, as well as hail.

As the storm intensifies, it is expected to move up the East Coast and reach southern New England by early Sunday morning, the Weather Service said.

Strong winds and wet snow are predicted for northern New England from Saturday night into Sunday morning, as lake-effect snows sweep across the lower Great Lakes into Monday morning.

Accumulations of six to 12 inches of snow in the Adirondacks in New York were possible starting late on Saturday afternoon, Mr. Chenard said.

“During the day tomorrow, it’s going to get cold behind the system and windy, and some snow showers will linger,” he added.

Forecasters said the New York City area could get up to two inches of rain into Sunday morning, with the highest totals expected in northeastern New Jersey. Peak rainfall is forecast from 8 p.m. Saturday and until early Sunday.

A steady rain will not last very long but will be “briefly heavy,” Mr. Chenard said, and will affect northern New Jersey, New York City and the Hudson Valley.

Minor to moderate flooding could come with high tides on Saturday evening and Sunday morning, along the western Long Island Sound, Jamaica and western Great South Bay, forecasters said.

Mr. Chenard added that it was possible for snow showers to move through New York City on Sunday evening, though any accumulation was unlikely.

“Expect heavy rain, coastal flooding and strong winds this weekend,” the National Weather Service of New York, N.Y., said on social media. “The potential for strong winds will linger behind the storm into Monday as well.”