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New York region digs out from bomb cyclone as polar vortex moves in

NEW YORK — The so-called "bomb cyclone" winter storm pounded parts of the New York area with over a foot of snow in areas, and is being replaced by the coldest air mass of the season that will see dangerous sub-zero wind chills for days.

States of emergency were declared in New York City, Westchester County and on Long Island, and in coastal New Jersey counties, according to the governors in New York and New Jersey.

Though the heavy snow has ended from west to east, powerful winds of up to 45 mph will continue through Friday, causing the blowing and drifting of snow and sending wind chills to as low as -10.

With the snow in place and not melting any time soon, and winds staying strong, serious risks to public safety remain. Dangers from downed power lines and trees, as well as snow-covered roads and sidewalks, will continue to pose a threat.

Sub-zero wind chills Friday through Sunday will increase risks of illnesses including frostbite and hypothermia,

In a sign of a quick return to normal, New York City Public Schools will be open on Friday, even as many school districts on Long Island, New Jersey and north and west are opting to close for a second day.

The snow started falling early Thursday and didn't relent until late afternoon.

Total Accumulations were as high as 15 inches for Long Island, coastal New Jersey and eastern Connecticut. Up to a foot fell on parts of New York City, with Queens taking the hardest hit. Other inland areas received a half a foot or more of snow, with lesser amounts the farther west and north you go.

Snow at its peak was falling at a rate of 2 to 3 inches an hour during the afternoon, with whiteout conditions common.

Blizzard conditions are marked by at least three straight hours of heavy or blowing snow, visibility less than a quarter mile and sustained winds of 35 mph or higher.

The snow was produced by a historic storm that resembled a hurricane and developed an eye-like feature. As cold air clashed with warm, pressure dropped in the storm, which brought dramatic strengthening.

This phenomenon is known as bombogenesis, and has led to this storm being dubbed the bomb cyclone. Bombogenesis is defined by a drop of at least 24 millibars in air pressure in 24 hours. This storm has dropped by 53 millibars in that time, Craig Allen points out. That means developed an intensity akin to Superstorm Sandy, but fortunately, the storm did not make landfall in he New York area.

The coldest air of the season is now moving in. Frigid temperatures will arrive on Friday with wind chill watches already being posted for the northern and western sections of the area. Wind chill temperatures will be as low as -15 for Saturday morning.

That'll keep the snow where it is at least through the weekend and the start of next week, according to the head of New York City's Department of Transportation.

"Once it falls, it is not going away," Commissioner Kathryn Garcia said. "We are going to see almost historically low temperatures this weekend" and a warm-up won't happen until Monday.

Daily highs haven't risen above 32 degrees since Christmas Day, according to the National Weather Service. There's a chance that the area could approach the record for most consecutive days with high temperatures being below freezing, the weather service said.

The longest stretch on record of below-freezing temperatures was 16 days, set back in 1961.