Weather

The pre-Christmas storm may shape up to be a bomb cyclone. Here’s what that means.

“Be careful if you’re out on the roads on Friday.”

Erin Clark / Boston Globe, File

December 20, 2022

A powerful storm system is expected to impact New England this week ahead of the holiday weekend.

What Boston meteorologists are saying about the timing and impacts of the storm

While the Arctic cold front is projected to bring heavy snow and blizzard conditions to much of the Midwest and Great Lakes and impact holiday travel plans, the Boston area is forecast to see rain Thursday night into Friday, though some higher elevations in Massachusetts could see snow.

Still, some forecasters are predicting the storm could become a bomb cyclone before it enters the Northeast and New England.

So what, exactly, is a bomb cyclone?

Kyle Pederson, a meteorologist with the National Weather Service Boston, said a bomb cyclone occurs when a low pressure system drops 24 millibars in 24 hours, or roughly one millibar (a measure of atmospheric pressure) an hour.

This meteorological change can also be called “bombogenesis,” he said.

“Usually that means the storm system is intensifying,” he told Boston.com of what happens when the pressure drops that quickly. “So you can expect the winds to be really ramping up and then also rain and [precipitation]. Our area won’t see any snow, but you could see, bomb cyclones can bring snow.”

According to the weather service, high terrains in northwest Massachusetts could see snow and ice if there is still enough cold air in place, but the precipitation we see from the powerful storm will likely just be rain.

As of Tuesday morning, Pederson said the weather service isn’t labeling this week’s storm a bomb cyclone, but he said it’s possible it could develop into one.

So far for the storm, which is predicted to arrive late Thursday and Friday, the weather service meteorologist said the biggest impact to the region will likely be the winds.

“[We] could see wind gusts Friday and Friday night up to 55, 60 mph, especially along the I-95 corridor,” Pederson said. “Another impact, especially coastal communities will want to keep an eye on, is coastal flooding. With this wind and also the high astronomical tides we could see some minor coastal flooding impacts. So those are the two biggest ones.”

The region could see up to 1 to 2 inches of rain from the storm, which could also result in some localized street flooding.

“Be careful if you’re out on the roads on Friday, especially with those high winds,” Pederson said. “You never know if a tree comes down or branches are coming down with these winds. I wouldn’t be too surprised if we have power outages on Friday, so just keep an eye out for those.”

Much colder and blustery, but dry, weather will follow on the heels of the storm for the rest of the holiday weekend, meaning most of the state won’t see a white Christmas. The weather service is predicting daytime high temperatures will struggle to reach the upper 20s to low 30s.