PORTLAND, Maine — The U.S. East Coast was beginning a whiplash-inducing stretch of weather on Wednesday that was rainy, windy and potentially dangerous, due in part to an atmospheric river and developing bomb cyclone.

Freezing Rain Gives Way to Deluge and High Winds

Parts of Maine experienced freezing rain that caused vehicles to slide off roads followed by a deluge of rain and unseasonably high temperatures — and the prospect of damaging winds — all in the same day, said Derek Schroeter, a forecaster with the National Weather Service. Some schools were closed across New England.

The heavy rain and fierce winds will last until Wednesday night, and flash flooding was a concern because of the deluge and melting snow, forecasters said. Utilities were also gearing up for potential power outages from damage caused by winds that could exceed 60 mph (97 kph).

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Atmospheric River and Bomb Cyclone Drive Extreme Weather

One of the key factors driving the weather is an atmospheric river, which is a long band of water vapor that can transport moisture from the tropics to more northern areas, said Schroeter, who’s based in Gray, Maine. New England was expected to bear the brunt as the storm tapped moisture from the Atlantic Ocean off the coast of the U.S. Southeast, and transported it to places like Maine, Schroeter said.

Forecasters also said the storm had the potential to include a process that meteorologists call bombogenesis, or a “bomb cyclone.” That is the rapid intensification of a cyclone in a short period of time, and it has the ability to bring severe rainfall.

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Treacherous Travel Conditions and Avalanche Warnings

The storm began with combination of fog and light freezing rain on Tuesday night into early Wednesday. Ice accumulated and travel became treacherous in parts of New England. A tractor-trailer carrying a load of oranges went off the Maine Turnpike in New Gloucester; the road was so treacherous that the oranges couldn’t be removed until a day later.

Parts of the Northeast were already preparing for bad weather.

In New Hampshire, the Mount Washington Avalanche Center issued a special bulletin Wednesday for the Presidential Range of mountains, which received significant snowfall over the last two weeks.

“Heavy rainfall could create dangerous and unpredictable avalanche conditions on steep snow-covered slopes,” it said, making for unsafe conditions on stream crossings, skiing and hiking trails and bridges.

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Flood Watches and Preparations Across the Region

A flood watch for Vermont runs from Wednesday afternoon to Thursday morning.

The city of Montpelier, Vermont, was advising residents to elevate items in basements and low areas that are prone to flooding. The city said Tuesday that it has been in contact with the National Weather Service and Vermont Dam Safety and “will be actively monitoring the river levels as this storm passes through.”

Ski resorts around the Northeast were preparing visitors for a potentially messy day on Wednesday. Stratton Mountain Resort, in southern Vermont, posted on its website that patrons “make sure to pack your Gore-Tex gear because it’s going to be a wet one.”