BOSTON — Airlines, officials and residents braced Thursday for potentially widespread coastal flooding from a major Nor’easter bearing down on a large swath of the East Coast.

Heavy rain, intermittent snow and high winds with gusts exceeding 50 miles per hour are expected as the storm moves up the Eastern Seaboard, beginning in New York and Connecticut on Thursday evening.

Massachusetts Gov. Charlie Baker activated 200 National Guard members to help with the storm.

“We’re expecting to see more severe flooding issues here than we did in the Jan. 4 storm,” when a Nor’easter lashed the region with heavy snow and rain, he said.

Locals were taking matters into their own hands. In Duxbury, south of Boston, officials urged residents to evacuate as soon as possible, and the fire department was preparing to use a high water rescue vehicle for the first time to help any residents who wind up stuck in homes during high floodwaters.

Michelle Shaffer, 45, of the coastal Massachusetts town of Hull, lost her appliances under 5 feet of water during the last big storm.

“I have a new washer, and my boyfriend just built a wooden platform for it. We got a couple of sump pumps,” said Shaffer, who planned to evacuate to high ground Thursday night.

“This storm is going to be worse because it’s going over three high tides,” she said.

The Coast Guard advised boaters to exercise “vigilance and extreme caution.”

In New Jersey, officials worried that the storm could take a chunk out of beaches just south of Atlantic City that are still being repaired because of damage from previous storms.

Across the East Coast, authorities told residents of coastal communities to be prepared to evacuate if necessary in advance of Friday morning’s high tide.

The National Weather Service said all of Rhode Island was under flood and high wind watches from Friday through Sunday morning.

Airlines were making their own preparations. Delta, Southwest, JetBlue, and American Airlines were allowing travelers to change their Friday and Saturday flights ahead of time to avoid delays and cancellations at key airports across the Northeast.

Regional power utilities said they had extra crews on standby to deal with expected outages.