Metro

The coming storms could be just the beginning of a nasty stretch of weather

Is a string of storms ahead? A solitary walker during one of last year’s storms.
Lane Turner/Globe Staff
Is a string of storms ahead? A solitary walker during one of last year’s storms.

It’s the calm before the storm. So enjoy it.

A small storm slipping by the state Friday followed by a second storm that is expected to bring a mix of wintry weather for Saturday night and Sunday are expected to usher in an unpleasantly cold, stormy period. And, yes, the reason is, once again, that dreaded polar vortex.

When is the nasty weather really going to start?

After this weekend’s storm, the weather in the Northeast will be chilly for a week, with a possible warmup as a storm system passes through around the middle of the week. But behind that, things are going to get downright cold.

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“It looks like we’ll be in a deep freeze” around the weekend of Jan. 26 and 27, Accuweather.com senior meteorologist Dave Samuhel said.

How long is the cold weather going to last?

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“That last week of January is looking really cold,” Samuhel said. “It’s when things really kick in, it sounds like.”

And from there? “We’re going to be in that cold weather pattern a good chunk of the time through most of February,” he said.

What about storms?

Along with the cold comes an increased risk of storms, Samuhel said.

“We’ll have to keep up our guard for possible coastal storms,” he said. “We could see a much greater nor’easter threat through the month of February.”

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“We’re just starting to get things rolling,” he said.

Last winter, when conditions were similar, a string of nor’easters hit New England in rapid succession.

What’s that about the polar vortex?

The cold weather is on its way because the polar vortex, a pool of very cold air that typically sits over the North Pole, is breaking into pieces and drifting south, Samuhel said.

“We’ll be dislodging a lot of cold air off the North Pole,” he said.

Why do we keep hearing about the polar vortex?

Jennifer Francis, senior scientist at the Woods Hole Research Center in Falmouth, said this year’s polar vortex changes resemble other breakouts that have happened in recent years.

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Francis says scientists increasingly believe climate change is to blame. Here’s how they think it works: As the Arctic warms rapidly, the westerly winds of the jet stream are disrupted, which in turn affects the polar vortex, causing it to bulge in places. The cold air tends to end up invading the East, while the West sees heat and drought.

“Lately we’ve been noticing an increase in the frequency of the breakdowns” of the vortex, said Francis, whose research suggests New England is headed for stormier — and sometimes bitterly cold — winters.

The polar vortex is being “disrupted in a big way” again this winter, she said, and “when that happens, we see a rash of extreme winter weather all around the Northern Hemisphere.”