What is a 'bomb cyclone'? Powerful nor'easter slams East Coast with violent winds, rain and snow

Grab your snow boots and umbrellas! Brutal winter weather – strong winds, rain and heavy snow – has hit much of the eastern U.S. and is expected to continue through the weekend.

Heavy snow, rain and potentially "dangerous" winds developed overnight across the Northeast and northern Mid-Atlantic regions, the National Weather Service (NWS) reported Friday.

"The air along the immediate coast will be warmer so a rain event is expected while interior sections of the northeast could get big snow totals," Fox News’ Senior Meteorologist Janice Dean said. "There is also the possibility that enough cold air will be pulled southward once the snow intensifies so a burst of snow is possible for places like New York City."

Parts of New York have seen over a foot of snow – and more may be on the way, NWS New York reports. High wind watches and warnings are up all along the entire I-95 corridor from Boston to Washington D.C.

The storm, similar to the blizzard that hit the East Coast in January, has been dubbed a “bomb cyclone” or "bombogenesis" by meteorologists as it is expected to rapidly intensify.

What is a “bombogenesis”?

The term "bombogenesis" is used by meteorologists to refer to a rapidly intensifying area of low pressure, Dean said.

“The central pressure of an area of low pressure [winter storm] must drop at least 24 millibars in 24 hours to qualify,” Dean explained. "Several major impacts will include strong winds, beach erosion and coastal flooding especially with high tide."

A millibar is the measurement of atmospheric pressure, according to the National Oceanic and Atmospheric Administration.

"This can happen when a cold air mass collides with a warm air mass, such as air over warm ocean waters," the National Ocean Service explains on its website. "The formation of this rapidly strengthening weather system is a process called 'bombogenesis,' which creates what is known as a bomb cyclone."

What does that mean for this winter storm?

The Eastern Seaboard is expected to be buffeted by wind gusts exceeding 50 mph, with possible hurricane-strength winds of 80 to 90 mph on Cape Cod. 

Heavy snow is continuing to fall in Ohio and upstate New York as the storm spins eastward. Boston and south to Rhode Island is forecast to get 2 to 5 inches of snow from the late-winter storm. 

Across the East Coast, authorities told residents of coastal communities to be prepared to evacuate, if necessary, in advance of high tides. The weather service said all of Rhode Island was under flood and high wind watches through Sunday morning.

Southern New England – from New Jersey to eastern Massachusetts – is also preparing for major coastal flooding.

The heaviest snowfall totals are expected to be in parts of western and central New York and northern Pennsylvania, where 8 to 12 inches is possible, Dean said.

New York City and Long Island are being rocked with heavy winds, some gusts reaching up to 70 mph. 

"Surge approaching 2.5 feet at both #Boston & #Nantucket as we approach high tide towards noon," NWS Boston tweeted early Friday. "Gusts increasing w/ 60 mph being observed at #Nantucket."

The storm killed at least five people, including a 77-year-old woman struck by a branch outside her home near Baltimore. Fallen trees also killed a man and a 6-year-old boy in different parts of Virginia, an 11-year-old boy in New York state and a man in Newport, Rhode Island.

How is the storm impacting the East Coast?

More than 2,100 flights were canceled by airlines, most spread across airports in the Northeast.

Delta proactively canceled 750 flights to and from the Northeast and New England Thursday night and Friday, and encouraged customers to check their flight status.

“The snow and heavy winds are forecasted to taper off late Friday night and Saturday,” Delta said in a statement online. “Delta will aim to rebound its operations in the region Saturday.”

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

"Dulles Airport has now reported gusts over 50 mph for over 12 hours straight. This is a rare occurrence," NWS Baltimore/Washington tweeted Friday night.

The storm knocked out power to 1.6 million customers from North Carolina to Maine. In D.C. alone, more than 100,000 customers lost power. The Office of Personnel Management closed all federal offices in the D.C. area for the day.

Republican 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.

Is this storm unusual?

It’s not unusual to get at least one storm that is classified as a “bomb cyclone” a year, Bryan Jackson, a meteorologist with NOAA's Weather Prediction Center, told Fox News in January.

The problem with this storm, though, is that it is going to be "slow and lumbering," Dean said. "This storm hasn't even gotten itself wound up."

Heavy rain, strong winds and "incredible amounts of snow" will continue to hit the Northeast thoughout the weekend.

Parts of Pennsylvania to parts of upstate New York are under winter weather watches with flood warnings all along the coastlines.

"The winds are going to cause big problems," Dean said, with some areas expected to face "hurricane-force" winds.

The Associated Press contributed to this report.