Forecasters are now predicting the northeast will plummet into a deep freeze.

The nation’s capital was at a standstill Tuesday evening as snow continued falling at a rate of about an inch an hour — while commuters across the Northeast struggled to get home through blizzard-like conditions and snow coming down harder and faster than many people expected.

The wintry wallop brought more than a foot of snow in some areas and another blast of arctic air, snarling traffic, closing schools and shutting down the federal government.

As the wind blows the snow around, it makes for very difficult visibility on Long Island. NBC News' Ron Mott reports from Syosset.

Initially forecast to be a modest blurt of cold weather, the system has intensified, unleashing wind-driven snow and frosty air on the Northeast Tuesday night into Wednesday.

The National Weather Service said Manalapan, N.J., got 15.5 inches of snow, Philadelphia got slightly more than a foot and Brookhaven, near Philadelphia's airport, got 15. It said parts of New York City had 10 inches.

In D.C., most offices of the government were shut down Tuesday — although the Supreme Court justices did show up for work — and officials were asking residents to stay off the roads.

"We've had about 80+ calls for personal injury collisions today," said Scott Graham, assistant chief of nearby Montgomery County, Md., Fire and Rescue, told NBCWashington. "Some of which have been very minor... turning out to be property damage; some more significant, with minor traumatic injuries, vehicles overturning."

The capital was set to see about a half-foot of snow and wind gusts of 30 mph, while Boston could see around 8 inches and wind gusts up to 40 mph.

Meanwhile, governors in Delaware, New Jersey and New York on Tuesday afternoon declared states of emergency as blizzard conditions hit along the heavily populated Interstate 95 corridor.

"This winter storm will bring a one-two punch of snow and extreme cold. I urge all those in the affected regions to exercise caution, and avoid travel if possible," New York Gov. Andrew Cuomo said.

New York broke three snowfall records Tuesday. And, for the first time since snow accumulation has been recorded in the 19th century, Philadelphia has had three 6-inch-or-greater snow events before Feb. 1.

NBC News' Al Roker has the latest forecast as the storm continues to deepen, creating blizzard-like conditions. As the arctic air tunnels in, the snow will eventually end, but it will still be blowing and drifting.

“Every once in a while these little winter storms go bananas, and we think this might be the one,” said Kevin Roth, a lead meteorologist with the Weather Channel.

The storm could bring up to 14 inches of snow to Philadelphia and southern New England and up to a foot in New York City through the night, to be followed by bitter cold as arctic air from Canada streams in. Washington was expecting 4 to 8 inches.

In Maryland, 11 inches had accumulated in Northeast Heights.

Up and down the East Coast, area schools and city and state governments hunkered down, but with more than 3,000 flights cancelled, many airports were virtual ghost towns as well.

More than 6,600 flights were delayed and another 3,342 were canceled by 11:30 p.m., according to FlightAware.com. More than 1,000 flights for Wednesday had already been nixed.

A winter storm warning was in effect for New York City and the surrounding areas by the National Weather Service from noon Tuesday through Wednesday morning, and Mayor Bill de Blasio said the city has activated all of its emergency preparation systems, according to NBC New York.

The heaviest snow was expected in the later afternoon into the evening. Overnight lows could reach the single digits with the wind chill making it feel like 5 below.

A shortage of propane gas in the Midwest and Northeast is impacting millions of homes and businesses in rural areas beyond the reach of utilities.

The storm has already led some school districts in Pennsylvania, New Jersey, Connecticut, Virginia, West Virginia and Kentucky to send students home early Tuesday or cancel classes ahead of time.

It has also forced New Jersey Gov. Chris Christie to scrap a party Tuesday night on Ellis Island in celebration of his second inauguration.

In Philadelphia, a Tuesday night game between the Philadelphia Flyers and Carolina Hurricanes was postponed due to the snow emergency declared in the city.

With federal workers in D.C. told to stay home, Tom Ripley, who works at a Washington hardware store, said his morning commute was cut in half because “there was almost no one on the road.”

He said the store was jammed Monday as customers stocked up on ice melt and shovels.

“Nobody prepares because we never get any snow, so the slightest chance of it, everybody freaks out,” Ripley said.

Coupled with the snow is another bone-chilling winter blast, but it’s not the same as the polar vortex that plunged temperatures to record lows two weeks ago. With the wind chill, the air will feel 10 degrees below zero or worse in some parts.

Temperatures “have already dropped 30 to 40 degrees across the Dakotas, Iowa and Minnesota, and 35 in Chicago,” Roth said. “That cold air is going to drop into the South and then there’s another surge of cold air coming on Friday.”

Meanwhile, lake-effect snow is expected in parts of Michigan and Indiana, with as much as a foot likely throughout parts of northern Indiana on Tuesday.

The storm began hammering the upper Midwest early Tuesday. When all is over, Southern Ohio is expected to get 3 to 5 inches, while the Central Appalachians — through West Virginia and western Maryland — could pick up 5 inches to a foot of snow.

In anticipation of the storm, Ohio Gov. John Kasich followed the lead of officials in 17 other states — mostly in the Midwest and North — who declared energy emergencies and loosened rules for propane.

In many of these states, residents are also being urged to cut down on propane use as supplies become limited.

While the eastern U.S. struggles with the snow, the West Coast will remain high and dry, Roth said. The ongoing ddrought om California has created ideal conditions for wildfires.

“Perhaps next week we can talk about rain coming to California,” Roth added.

Brian Snyder / Reuters A pedestrian walks through the falling snow in Medford, Massachusetts.

NBC News' Becky Bratu and Elisha Fieldstadt and The Associated Press contributed to this report.

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