A winter storm headed to the Northeast late Sunday and could continue into Tuesday, plastering the corridor from Philadelphia to Boston with heavy snow.
Snow totals in that span could be 18 inches or more, depending on an influx of relatively mild air from the Atlantic Ocean.
The storm system has brought eight inches of snow in Chicago and was expected to approach the Canadian border on Sunday.
The low-pressure area that will bring the heavy snow, strong winds and potential for coastal flooding to the Northeast will spend Sunday getting organized in the Mid-Atlantic region, where snow was falling in the nation’s capital. Washington was poised to receive more snow in one day than the city has seen in two winters.
The storm has brought wild weather across the Lower 48, first driving an atmospheric river ashore in California last week with extreme snow totals topping 100 inches in the Sierra Nevada. From there, it brought severe thunderstorms to the Southwest and tornado activity to Oklahoma, while a dust storm in its wake caused visibility to plummet Saturday in parts of Texas.
Now the main low-pressure area is transferring its energy offshore into a coastal system, also known as a nor’easter, that will intensify and move north up the coast.
Winter storm warnings for heavy snow were in effect from the mountains of North Carolina through southwestern Connecticut, while watches extend all the way to northern Maine.
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Snowfall rates increased rapidly in Philadelphia as the offshore low-pressure system strengthened Sunday. Computer models showed a band of heavy snow forming between Philadelphia and Rhode Island on Sunday night into Monday.
Forecasters said milder marine air drawn inland could bring mixed precipitation to Philadelphia, including sleet or freezing rain, early Monday before it changes to rain and temporarily ends. Snow will fall most heavily immediately before that changeover, with rates of at least an inch an hour.
In New York, heavy snow was expected early Monday. Uncertainty remained about a potential changeover to a wintry mix or rain about midday.
If that transition does occur, snowfall amounts would stack up to a bit more than a foot. If not, more significant accumulations would be probable – perhaps 18 inches or more.
The National Weather Service included New York in an “extreme impact” zone on its outlook map, citing the potential for “extreme disruptions to daily life.” Forecasters said most of the surrounding tri-state area can expect “major impacts” from the storm system.
In Boston, more than a foot of snow is expected.
President Joe Biden was briefed Sunday on the storm, according to the White House.
Some computer models suggest that cold air will remain entrenched in New York for the duration of the event, portending a historic snowstorm. Such heavy snowfall could shut down city streets and cancel flights at the region’s major airports.
“Despite the fact that we are forecasting up to 18 inches of snow, these numbers are conservative” if you trust some computer models, wrote the National Weather Service office in New York.
If New York were to pick up 19.8 inches or more in 48 hours, it would qualify as one of the 10 heaviest snowfalls on record in the city. The top spot of 27.5 inches is held by a Jan. 22 and 23 storm in 2016.
“This weather will be serious. If you can stay home, stay home,” Mayor Bill de Blasio, a Democrat, tweeted Sunday.
Snowfall amounts will vary significantly depending on where the narrow corridors of heaviest snowfall, known as snow bands, set up and stall. In the heaviest bands, rates of one to two inches per hour or more are likely. Eastern Pennsylvania is also likely to see heavy snow, including in places such as Harrisburg and Allentown.
Some areas in northern New Jersey could see more than two feet of snow as moisture from the Atlantic is drawn westward, directly into much colder air.
Snow will ease overnight Monday into Tuesday, but light snow is probable most of Tuesday morning into the afternoon.
The most snow could fall in New York City, while encompassing the southern Hudson Valley and most of central and eastern Pennsylvania.
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Hartford, Conn., could get a foot of snow or more.
Farther northeast, in the Providence-to-Boston corridor, meteorologists were grappling with predicting the finicky rain-snow line. Snow will arrive there Monday midmorning, with the steadiest and heaviest precipitation occurring overnight before winding down midmorning Tuesday.
During the storm, the rain-snow line may wiggle near Interstate 95, with mixing possible in Boston and Providence.
Storm totals of 12 to 18 inches are expected just west of Boston, with the biggest wild card being the amounts in Boston itself and along the coastline. With onshore winds of up to 60 mph, tall waves and coastal flooding will affect the New England shoreline, leading to the potential inundation of vulnerable areas.
The storm is expected to spread snow into northern New England, benefiting ski areas in Vermont, New Hampshire and Maine.
Conditions will clear later Wednesday before milder weather late in the week.