New York, Boston, and much of New England could face a weekend nor’easter storm with wind gusts of 70mph in places, and “significant” impacts including beach erosion, flooding, and power outages, forecasters warn.

Effects from the season’s first such storm since Tuesday’s official start of fall could last through the weekend, especially if the system sits swirling off the coast, a scenario experts say is looking increasingly likely.

“If the storm nearly stalls, several days of persistent onshore winds and pounding surf could take a significant toll on beaches and vulnerable coastal communities, especially with astronomical high tides coinciding,” said Alyssa Glenney, an AccuWeather meteorologist.

The online weather service predicted “a long-duration storm for many areas along the mid-Atlantic and New England coasts”, with impacts beginning late Wednesday, spreading to New England late Friday or Saturday, and lasting through Sunday in some places.

The Weather Channel said coastal flood alerts were in place across the mid-Atlantic, and winds were likely to bring sea rise up to 3ft above normal levels. But it said uncertainty remained about exactly where the system would be at the end of the week.

“Forecast models are picking up on the low, but two models show that the timing and duration of the storm could differ,” the Weather Channel said on its website, weather.com.

“The European model brings the low close to the coast as a strong storm, but it moves slower. It could even meander around the east coast until it fizzles. Under this scenario, there would be more time for strong winds to cause significant power outages, heavy rain-induced flooding, and coastal erosion.”

The GFS model, meanwhile, brings the storm in faster, and approaching New England by Saturday afternoon.

“A faster storm could mean winds, rain and coastal erosion would be less severe and lessen disruptions to travel and weekend plans,” the Weather Channel said. “However, this model calls for a stronger storm by the end of the weekend as it moves away from the north east, meaning some coastal areas could experience longer-lasting impacts.”

Nor’easters are more prevalent from September to April, the National Weather Service said. They usually develop within about 100 miles of the cost between Georgia and New Jersey, and progress steadily north eastward, typically attaining maximum intensity near New England and the maritime provinces of Canada.

AccuWeather’s forecasters agreed with the Weather Channel that the exact track of this weekend’s storm remained important for communities farther inland.

“A track closer to the coast could bring heavier rain, stronger wind gusts and travel disruptions from Washington DC and Philadelphia, to New York City and Boston, while a track farther offshore would limit inland rain and wind impacts,” the service said.