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Nor’easter could wallop New England with heavy snow and wind Saturday

Odds are increasing that a foot of snow could fall near the coastline, with possible blizzard conditions

The American (GFS) model shows a storm developing well offshore the Mid-Atlantic on Saturday morning, with snow along the coast from the Delmarva to New England. (PivotalWeather)
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New England is bracing for what could be a major winter storm on Saturday, with heavy snow, strong winds, blizzard conditions and coastal flooding all within the realm of possibilities. The Mid-Atlantic could be dealt a dose of light snowfall, too, though computer weather models are concentrating their ire farther northeast.

It’s worth emphasizing that at four days out from the incipient storm, a lot can change — but the stakes are high enough that it’s worth raising awareness for a potentially high-impact system. The zone from eastern Long Island to eastern Maine, including Providence and Boston, is particularly at risk.

A “significant winter storm is possible Friday night and Saturday,” the National Weather Service in Boston wrote Tuesday morning in an online forecast discussion but cautioned against taking early predictions as set in stone. “For now, what you can do is prepare for the potential of an impactful snowfall with accompanying strong winds.”

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Astronomical tides also will be high Saturday, making coastal flooding a greater concern even if the rapidly developing system shifts out to sea.

Computer model forecasts have generally nudged the storm track eastward, compared with Monday, somewhat reducing the chance of heavy snow outside eastern New England, but it will take another day or two for greater confidence in the exact track.

A more offshore track increases the likelihood that coastal locations in eastern New England see mostly snow rather than a switch to rain or sleet, while reducing potential snowfall farther west into western Massachusetts, Vermont and New Hampshire.

Tracking the ingredients

More than 72 hours remain before the storm begins to take shape off the southeast and Mid-Atlantic coast, but the ingredients are already beginning to materialize on weather maps.

Two atmospheric disturbances are soon to move ashore over extreme northwestern North America. The first was approaching the Seward Peninsula near Nome, Alaska, and the second had just slipped east of the Aleutians.

The former will scoot southeast over central Canada, while the other will dive farther south and pass over the Four Corners region Thursday. The development of a major storm is predicated on both systems overlapping over the Appalachians early Saturday. That will help intensify a storm developing off the Mid-Atlantic coast.

Meanwhile, high pressure will build over eastern Canada into Thursday and Friday, feeding the cold air instrumental for snow into the Northeast.

There are signs that the storm will become a “bomb cyclone,” or a storm that rapidly strengthens as it charges up the Northeast coast, triggering a dramatic drop in air pressure. Abnormally warm water in the Gulf of Maine could help energize the storm and increase its intensity.

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An early look at the forecast

It’s too early for the Weather Service to hoist winter storm watches or warnings, and forecasts offering specific numbers for snow totals are impossible in this time frame. That said, we can paint an early picture of what to expect based on the simulated odds of heavy snow from large numbers of computer model projections.

Washington and Baltimore:

Light snow may break out Friday afternoon. It could briefly become moderate, especially along and east of Interstate 95 on Friday evening. The storm will possibly develop too far offshore for significant accumulations of more than an inch or two; areas over the Delmarva Peninsula have the potential for more.

In the event that the merging of the two parent weather disturbances occurs earlier than currently anticipated, more substantial snow would be possible.

Chance of at least one inch: 40 percent | Chance of at least three inches: 20 percent | Chance of at least six inches: 10 percent

Philadelphia

Philadelphia, being farther northeast, could see a bit more snow than Baltimore and Washington but still may be too far west to see much before the system rapidly gains strength south of New England. Some light snow is possible Friday evening, potentially coinciding with the evening commute. If the storm develops quickly, snow could continue Friday night with a few inches of accumulation.

Chance of at least one inch: 50 percent | Chance of at least three inches: 30 percent | Chance of at least six inches: 15 percent

New York City

The Big Apple could be close to the zone where substantial snow starts and stops. The odds will increase just to its north and northeast, but a blitz of heavy snow and strong winds, gusting over 40 mph, cannot be ruled out. If heavy snow develops, it would be during the day Saturday; lighter snow will probably develop Friday night.

Chance of at least one inch: 60 percent | Chance of at least three inches: 35 percent | Chance of at least six inches: 25 percent

Providence, Boston and Portland, Maine

The greatest propensity for a higher-end winter storm will exist along the Interstate 95 corridor from Rhode Island through Boston and coastal New Hampshire and Maine. Patchy light snow may begin late Friday night expanding from south to north, and snowfall may become moderate to heavy by sunrise Saturday.

Significant accumulations of at least 6 to 12 inches are possible before the storm pulls away Saturday night. Blizzard conditions, with accompanying winds over 50 mph, could develop if the storm isn’t too far offshore.

Chance of at least one inch: 80 percent | Chance of at least three inches: 65 percent | Chance of at least six inches: 55 percent | Chance of at least 12 inches: 25 percent

Interior New England

While it will certainly be cold enough for snow, whether any precipitation ultimately falls will hinge on the track of the system. Locations from western Connecticut through the Berkshires, Vermont, New Hampshire and far-western areas of Maine may get brushed with light snow if the storm tracks far offshore but could see more substantial amounts if it comes closer to the coast. (The probabilities shown below are highest in eastern areas and lowest in western areas of interior New England.)

Chance of at least one inch: 45 to 75 percent | Chance of at least three inches: 35-60 percent | Chance of at least six inches: 25-50 percent

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