A winter storm taking aim at the Mid-Atlantic and Northeast from Wednesday night into Thursday is likely to dump more snow in about 24 hours than Philadelphia and New York City recorded all last season. It may also produce a significant snowstorm in Boston.
A foot to a foot and a half of snow is possible from this event in New York City as a strong low-pressure area moves along the New Jersey coast and drifts east-northeast, allowing an ample supply of cold, dry air to feed into the storm and keep precipitation in the form of snow. That would more than double the snowfall totals from last winter, when the city received just 4.8 inches in the entire season. The bulk of the snow is expected to fall Wednesday night into early Thursday.
The National Weather Service is predicting blockbuster snowfall totals to the northwest of Interstate 95 and south of Interstate 78 in Pennsylvania and northern New Jersey, including a stretch from Lancaster, Pa., to Harrisburg and northeastward to Caldwell, N.J. The Poconos may even see some snow totals approaching two feet, given the likelihood of snowfall rates in the most intense snow bands to exceed one to two inches per hour.
In a forecast discussion, the Weather Service forecast office in Philadelphia stated that “this area would currently be in the ‘sweet spot’ for heavy snow,” since it will be closest to the region of maximum rising motion in the atmosphere, along with a deep layer of cold air from the surface to several thousand feet in the air.
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For Philadelphia, the forecast is far trickier but also snowier than it is for Washington. As of Monday afternoon, the Weather Service was forecasting about six to eight inches of snow and sleet to accumulate in the city, with lower amounts to the east and greater amounts just to the west. Precipitation may begin in Philadelphia on Wednesday afternoon and end before dawn Thursday.
The latest update on the expected nor'easter Wednesday-Thursday. For many areas this will be the first significant snowfall of the season. If you must travel, please exercise extra caution, and review your winter driving safety procedures. pic.twitter.com/mnRJZALKYf
— NWS Eastern Region (@NWSEastern) December 14, 2020The precipitation transition zone between all snow and a wintry mess is expected to be draped across I-95, based on computer models and forecasts from Weather Service offices.
Forecasters are watching for the possibility of a “warm nose” of air aloft, a layer of relatively mild air flowing from east to west off the Atlantic at about 5,000 feet above the ground that can turn snow into sleet, freezing rain or rain, cutting down on snowfall totals. In other words, a warm nose is a snow lover’s nightmare.
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How far west that warm layer pushes will help determine the final snowfall totals, and there is still quite a bit of uncertainty about this in advance of the storm.
For New York City, the forecast is slightly more clear-cut, though not without a bust potential. Heavy snow and gusty winds are expected in the city and points north and west starting Wednesday afternoon and continuing into Thursday morning, with a foot or more possible in the city. Snow may mix with sleet and rain, and it may change over to rain for a time on Long Island, limiting accumulations there.
The last time the city picked up a foot or more of snow was in 2018, when 14.8 inches fell during a storm March 13 and 14.
The Weather Service is cautioning that there is some uncertainty about mixed precipitation making its way into the metro area, which would reduce snowfall totals somewhat.
[Monday Afternoon Update] Here's our initial thinking on how much snow we see in SNE Wed night-Thu. A Winter Storm Watch has been posted where we have the most confidence in seeing >6 inches of snow and may be expanded later. *Check back since these amounts will shift!* pic.twitter.com/3oOJb8170I
— NWS Boston (@NWSBoston) December 14, 2020The storm looks set to deliver significant snow throughout Connecticut, Rhode Island and much of Massachusetts, though questions remain about the northern extent of the heavy precipitation. Weather Service forecasts for Boston show about eight to 12 inches falling there, with higher amounts south of the city, in northern Rhode Island and much of Connecticut.
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Computer models have been consistently projecting a heavy band of snow forming along the southern coast of New England and meandering its way northward toward the Massachusetts Turnpike, enhancing snow totals along and south of there.
The snow in Massachusetts will be fluffier than what falls in the big cities to the south, because the air will be colder and drier here throughout the event.
Accumulating snow, most likely to begin Wednesday evening, could linger in eastern Massachusetts through much of the day Thursday as the low-pressure area slowly weakens and shifts to the east, away from land.
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