But it’s not just New York City that will take a hard hit.
Some areas, including Washington, DC, with slightly warmer temperatures, will instead see a wintry mix.
But Philadelphia and New York City could see up to 16 inches of snow, Javaheri added, while Boston could see up to 12 inches.
“These sort of early season snow accumulations are rather rare for a pre-Christmas time period,” Javaheri said. “If Boston records more than 12.5 (inches) of snow, it would place it as (a) top-five snowstorm for any date on record before December 25.”
“This will likely lead to very dangerous, is not impossible travel conditions and isolated power outages,” the service said.
Impacts in some areas could be extreme: with travel disruptions, widespread power outages and damage to homes from falling trees all likely across the Mid-Atlantic, southeastern New York state, and southern New England.
Heavy rainfall could also cause flooding in parts of the Mid-Atlantic, the service said.
By Thursday morning, the storm will be tracking into the Atlantic, while some snowfall may linger in parts of New England.
‘Be ready for a disruptive storm’
More than 70 million people, from Georgia to Maine, are under some sort of winter-weather advisory or warning.
In Pennsylvania, where Covid-19 vaccine delivery efforts are underway, Gov. Tom Wolf signed a winter weather emergency proclamation, adding power outages were a possibility.
“Models predict that the first significant winter storm in nearly a year will hit Pennsylvania tomorrow,” the governor said in a statement. “The commonwealth’s emergency preparedness teams have spent a great deal of time and energy over the last several months supporting efforts to mitigate the COVID-19 pandemic and help the commonwealth weather this public health emergency and ensure vaccines are delivered as planned.”
“This proclamation makes it easier for all of those involved in vaccine delivery and keeping people safe to do their jobs,” he added.”
De Blasio urged residents to take precautions ahead of the storm, saying the city could see blizzard-like conditions Thursday morning with “really bad visibility, intense wind, intense snow.”
“You need to be ready for a disruptive storm,” he said during a news conference Tuesday. “I want people to right now be thinking about the precautions you’re going to take, the ways you’re going to change your routine. Take this seriously.”
Connecticut Gov. Ned Lamont warned against unnecessary travel, and announced the State Emergency Operations Center, already working virtually throughout the pandemic, will remain activated to monitor storm conditions.
“With heavy and steady snowfall expected starting on Wednesday evening, the Department of Transportation is activated and prepared to clear and treat our roadways,” Connecticut Transportation Commissioner Joseph Giulietti said in a statement.
“Driving conditions will be treacherous at best and downright dangerous at worst. The best thing the public can do is sit this one out and let our crews do their jobs,” Giulietti added.
CNN’s Rob Frehse and CNN Meteorologist Michel Guy contributed to this report.