A historic blizzard is about to shut down the Northeast with up to 2 feet of snow

Thundersnow is a rare, localized snowy thunderstorm that happens with a larger, very powerful winter storm or intense lake-effect snow.

Typical thunderstorms are fueled by atmospheric instability. Heat and moisture generate this instability, so that’s why thunderstorms are more common during warmer parts of the year.

But very powerful storms, like this budding nor’easter, can generate plenty of atmospheric instability on their own because they’re so energetic and chaotic.

Thundersnow’s lightning typically flashes within the storm itself, but some bolts have been known to strike the ground.

It also doesn’t quite have the same loud boom as a regular thunderstorm because heavy snowfall muffles the sound. Instead it sounds like a low, ominous rumble.

The 1 a.m. run of the American GFS model predicted it would be snowing in Washington, DC, by 7 a.m. As of around 11:30 a.m., it’s still raining there, which give us an indication the model was running much colder than reality. This means the GFS snow forecast is likely too high.

The Euro, on the other hand, predicts rain changes to snow in the late afternoon, early evening.

NYC Mayor Mamdani assists with salting operation ahead of historic blizzard

00:29 • Source: CNN

NYC Mayor Mamdani assists with salting operation ahead of historic blizzard

00:29

New York City Mayor Zohran Mamdani had an early start on Sunday preparing the city for a historic blizzard.

“NYC has over 100 step streets — many in the hills of the Bronx — and NYC DOT works hard to keep them safe,” Mamdani shared on X.

“Grateful to the crew at the DOT Brush Avenue Yard for walking me through their salting operation as the first snow starts to fall. Public service in action,” he said.

Mamdani also visited the New York City Department of Sanitation shed in Flushing, Queens, while they prepared their fleet of snowplows.

“New York’s Strongest adds snow chains to over 2,200 vehicles and loads over 700 salt spreaders to treat and clear our streets,” he said.

Boston Mayor Michelle Wu is urging residents to stay home and keep roads clear ahead of a significant winter storm set to begin tonight.

Wu said the city is declaring a snow emergency and is implementing a parking ban starting at 2 p.m. ET today. “Starting at that time, all vehicles parked along snow emergency arteries will be towed,” she said.

Workers are already out pretreating the roads, and the city will have “more than 900 spreaders, plows and other pieces of equipment on the roads for the storm,” the mayor said.

“Please make plans to stay inside. Stay warm. Do not be on the roads,” Wu said, citing potential whiteout conditions. “Let the plows do their work,” she said.

Wu also announced that all Boston Public Schools will be closed tomorrow, February 23. Central offices and all BPS extracurricular activities are canceled today and Monday, she added.

Boston City Hall and all municipal buildings will also be closed tomorrow, as well as Boston Library branches.

Westchester County in New York will institute a “complete road ban” overnight, officials announced on X.

“The road ban is being implemented due to hazardous winter weather conditions expected overnight, including heavy snowfall and wind,” reads the X post. “Roads are closed to all but essential travel (police, fire and ambulance).”

The ban will start at 9 p.m. ET tonight and end at 10 a.m. ET tomorrow morning.

Westchester County is in southeastern New York state, bordering Connecticut.

Temperatures closer to the ground will still be above freezing when rain changes to snow in the Washington, DC, area this afternoon.

Since those first snowflakes won’t accumulate, the local National Weather Service office described it as a “white rain.” All it will do is wet roads, just like rain would.

Wet roads can still be hazardous for drivers, but they won’t get slick from snow until temperatures turn colder tonight. About 2 to 5 inches of snow is possible in the metro area, which could slow the Monday morning commute.

Shoveling snow is hard and it’s even more difficult if the snow isn’t powdery or fluffy like with this storm.

Meteorologists describe how wet or dry snow is through its snow ratio. A higher snow ratio, say 20:1, means 20 inches of snow occurs for every inch of water. That snow is very dry and fluffy. A lower snow ratio of 6:1 means that the snow is quite wet and will only produce 6 inches of snow for every inch of water.

The last storm to rock the Mid-Atlantic and Northeast exactly four weeks ago dropped very fluffy snow because it was extremely cold at the time, which kept snow ratios high. Temperatures are going to be much closer to freezing during this storm, meaning snow ratios will be much lower.

Heavy, wet snow is called heart attack snow because cleaning it up puts a massive strain on the body — especially the heart. People with heart conditions or even high blood pressure could quickly run into issues while shoveling, especially if it’s cold.

Shoveling snow is responsible for as many as 100 deaths on average each year, according to the nonprofit National Safety Council.

The American and European models were at extreme odds Friday morning, just 48 hours before this storm was slated to start. The spread between the two forecasts was a paralyzing I-95 blizzard on the one hand (American model) and a largely forgettable bout of light snow on the other (European).

The models have converged since then. The American GFS was out to lunch in some of its wild predictions (30 inches in DC? Really?), but the Euro was likely way too light and has adjusted its snow forecast higher over the past two days.

The reason for the starkly divergent forecasts could be traced to subtle differences in how the models were resolving pieces of atmospheric energy diving south out of Canada and a high pressure area over the Rockies. What we don’t know is why they were seeing things so differently.

No matter the outcome, we know this will get some Monday-morning quarterbacking in the weather world. We also won’t be surprised if a few officials say some public things about what little time they had to prepare.

There will be bands of more intense snowfall rates within the storm’s large footprint Sunday evening into Monday morning.

Under those bands, snow could pile up at rates of an inch per hour beginning around 8 p.m. Sunday in the mid-Atlantic, then spreading as far north as southeast New England by 4 a.m. Monday. Even higher rates of 2 to 3 inches per hour are possible in spots.

The computer model forecast above shows there’s a 60% or better probability of snowfall rates hitting at least an inch per hour in the light green, yellow, orange and red shadings. That includes Philadelphia to New York City and Boston.

Wherever these intense bands set up will hit the snowfall jackpot, seeing the higher end of the predicted range — around 2 feet in most places.

As a blizzard approaches, power outages are a real possibility across the Northeast. Even moderate snow or ice can knock out electricity.

Here are some safety reminders:

Read the full story on mistakes to avoid during a winter storm here.

Not every snowstorm is a blizzard; it has a technical definition.

A blizzard needs:

These conditions need to last for at least three consecutive hours.

A blizzard can also happen if it’s not actively snowing but there’s plenty of snow on the ground — that’s called a ground blizzard. They occur when already-fallen snow is blown around in the same wind conditions and for the same duration as the above definition.

Snow falls at a subway station in New York, on Sunday.

Sunday: Rain and light snow will continue this morning in New York and the Mid-Atlantic. Places seeing rain will mix with and then change to snow as colder air arrives through the afternoon.

Sunday night: Conditions go downhill dramatically into the overnight hours as the storm intensifies quickly. Snowfall rates of 1 to 3 inches per hour expand from the Mid-Atlantic to southern New England. Whiteout conditions are possible given the heavy snow and intense wind.

Monday morning: Philadelphia to New York City and southern New England are getting hammered with snow and strong wind. Travel will be dangerous or impossible, with blizzard conditions ongoing.

Monday afternoon: The storm eases up from south to north and will largely be wrapping up by the evening, though parts of New England will still be seeing the last of its impacts.

The sun rose this morning on the early stages of what will become a blockbuster, potentially historic nor’easter.

The storm was centered just off the coast of North Carolina at sunrise. It’s going to explode in strength later today and become a bomb cyclone overnight.

The storm’s clouds stretch much farther than where its center is.

Notice the comma-shaped cloud pattern? The bulk of clouds appear from the Northeast to the Carolinas with a thinner line of clouds stretching all the way to the storm’s moisture source over the Gulf.

Over 35 million people across the Northeast are under blizzard warnings for the combination of intense snowfall rates and damaging winds from the incoming bomb cyclone.

Technically, for there to be a blizzard, you need sustained winds or frequent gusts of at least 35 mph and visibility to be a 1/4 mile or less for at least 3 consecutive hours.

These sorts of conditions are rare and only found in the most potent of winter storms, so blizzard warnings are also rare.

It’s been years since the Northeast has seen such widespread blizzard warnings, or warnings at all, according to the National Weather Service.

• New Jersey: The entire state is under a blizzard warning for the first time since January 1996.
• Delaware: The entire state is under a blizzard warning for the first time since Feb 10, 2010.
• Philadelphia: The city is under its first blizzard warning since January 2016.
• New York City: This is the first blizzard warning including Manhattan since 2017.
• Boston: The city is under its first blizzard warning since 2022.

New York City’s Department of Sanitation is rolling out new tactics as a second significant snowfall in less than a month bears down on the city.

In a Saturday advisory, the agency said it plans to hire more than 1,000 emergency snow shovelers after stepping up recruitment efforts in recent weeks. The temporary workers will support snow removal operations on both overnight and daytime shifts.

Walk-in registration will be available this weekend, with no appointment required, according to the advisory. Those interested in becoming paid emergency shovelers can check eligibility requirements and report to a local sanitation garage with the necessary paperwork by 1 p.m. ET Sunday.

Workers are paid to clear snow and ice from bus stops, crosswalks, fire hydrants and other public areas. Compensation starts at $19.14 per hour and rises to $28.71 per hour for any hours worked beyond 40 in a week. Applicants must be at least 18, eligible to work in the US and able to perform heavy physical labor, according to the sanitation department.

Philadelphia Mayor Cherelle Parker declared a snow emergency starting at 4 p.m. ET Sunday. Government offices and courts will close Monday, schools will shift to virtual learning, and trash and recycling collection will be delayed, Parker said in a Facebook post.

Officials plan to deploy more than 1,000 personnel at the storm’s peak, according to Parker, with crews focusing on sidewalks, pedestrian passages and accessible ramps.

“We will do whatever it takes, however long it takes to ensure that we have cleared our streets and we are keeping Philadelphians safe,” Parker said during a news conference Saturday.

Parker urged drivers to move their vehicles off snow emergency routes and help ensure roads are clear for plows.

The city’s equipment fleet includes front-end loaders, skid steers — commonly known as bobcats — and a range of plow trucks from pickups to heavy machinery, Carlton Williams, director of the Office of Clean and Green Initiatives, said Saturday.

Philadelphia has over 25,000 tons of salt on reserve, the mayor said.

Williams added the city has secured two snow melters that will be strategically placed in dense residential areas where snow cannot simply be plowed and instead must be removed.

School districts across the Northeast are canceling in-person classes ahead of the powerful blizzard expected to peak by Monday morning.

In Pennsylvania, Philadelphia Mayor Cherelle Parker said School District of Philadelphia buildings will be closed Monday, but students will shift to virtual learning.

Yonkers Public Schools — New York’s third-largest district — announced all schools and central office facilities will be closed Monday due to the blizzard warning.

A decision on remote learning for public schools in New York City will be announced by noon Sunday, according to Mayor Zohran Mamdani.

In New Jersey, Hillside Public Schools said all schools and administrative offices will be closed Monday following the governor’s declared state of emergency.

At least two districts in Connecticut — Meriden Public Schools and Tolland Public Schools — also announced closures for Monday as the storm approaches. CNN affiliate WBZ-TV is maintaining a running list of school cancellations across Massachusetts and southern New Hampshire, while WFSB is tracking additional closings in Connecticut.

Ahead of what could be New York City’s most significant winter storm in years, Mayor Zohran Mamdani has urged residents to start preparing immediately.

New York Gov. Kathy Hochul declared a state of emergency for 22 of the state’s 62 counties.

Meanwhile, New York City officials are bringing in outside snow-clearing equipment, and more than 40 warming centers will open across the five boroughs as outreach teams ramp up efforts to bring homeless New Yorkers indoors. This is the first blizzard warning issued for New York City proper since 2017.

On Saturday, Mamdani said the city is operating under an enhanced Code Blue and that its winter weather plan is fully activated. The Department of Sanitation has mobilized its full plow fleet and activated more than 2,200 emergency snow shovelers in advance of the storm, with more than 1,000 additional shovelers set to deploy Sunday night, he added.

The mayor said the city is mandating at least four feet of clearance on sidewalks to accommodate wheelchairs and expanding tracking of bus stops, pedestrian ramps and crosswalks.

He added snow-clearing crews for Citi Bike stations are being increased and urged property owners to salt their sidewalks and clear snow promptly.

A bomb cyclone is a rapidly strengthening storm that undergoes a significant drop in pressure – one measure of a storm’s strength – in a short time. They often unleash strong winds, heavy snow and rain, and the one developing off the Southeast coast right now is no different.

A storm’s pressure must drop at least 24 millibars (a unit of pressure) in 24 hours or less to undergo bombogenesis or “bomb out” and meet the bomb cyclone criteria. Technically, the exact millibar drop needed varies slightly based on the storm’s exact latitude, but 24 millibars in 24 hours is the accepted threshold.

This storm’s pressure is forecast to drop around 35 or more millibars in 24 hours from Sunday morning into Monday morning.

Bomb cyclones typically form over oceans where very cold air from land clashes with warmer air over the water, but they occasionally pop-up over land. They most commonly develop in late fall, winter and early spring.