After basking in 70-degree temperatures in February, residents of the Mid-Atlantic and Northeast are in for one heck of a rude awakening early this week, as a powerful storm takes shape off the East Coast. In all, almost 50 million people could see a foot or more of snow from this storm.
While there is still some uncertainty in the details, it's clear that areas from Washington, D.C. to Boston are likely to be walloped by an intense winter storm bringing heavy snow, strong winds, coastal flooding and possibly, for a time anyway, a changeover to sleet or rain.
Computer model runs on Sunday have locked on to a scenario for this event that would bring blizzard conditions to areas from New York City to Boston. The storm track depicted by most of the more reliable computer models would also dump heavy snow in parts of Maryland, eastern Pennsylvania, New York state, Vermont, New Hampshire and Maine.
This storm is likely to bring several cities to a grinding halt on Tuesday, with flight cancellations and possibly even subway closures in New York and Boston, especially if blizzard conditions do materialize.
All of this snow will come courtesy of a storm that will rapidly intensify as it moves off the Mid-Atlantic coast on Monday night, to a position near or southeast of Nantucket, Mass. by Tuesday evening. This track should keep most areas along and west if I-95 all snow, with 6 inches or more a possibility in the nation's capital, which has had a nearly snowless winter so far.
Farther north, snowfall amounts will increase, with a foot to a foot-and-a-half projected from just northeast of Philadelphia northward into Boston.
The key ingredients for this event are already getting into place. First, an Arctic high pressure system is moving into position across southeastern Canada and northern New England, so the cold air will be in place for snow. Some cold temperature records have been set across New England this weekend as the air mass settled in from Canada.
Second, two atmospheric disturbances, one riding the northern jet stream out of Canada, and the other surfing the southern jet from the Gulf of Mexico, now appear destined to meet up and combine forces to form a single, strong storm.
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However, subtle shifts in this atmospheric mating ritual, known to meteorologists as "phasing," can make a big difference in where the surface low pressure area forms and where it moves. This can, in turn, affects snowfall totals.
For example, a more offshore track, as hinted by computer models on Saturday afternoon, could spare areas northwest of New York City and Boston from the heaviest snow. A track closer to the coast could introduce issues with precipitation type along coastal areas.
Blizzard watch for NYC, Boston
With the potential for a crippling snowstorm in the nation's biggest cities, the National Weather Service is not taking any chances. Winter storm watches have been issued for Monday night through Tuesday night from Washington north into New England, and a blizzard watch is in effect for New York City, coastal New Jersey, Long Island, coastal Connecticut and coastal Massachusetts all the way into the city of Boston.
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To qualify as a blizzard, a storm must bring a prolonged period of three hours or more in which falling and/or blowing snow reduces visibility to one-quarter mile or less, and sustained winds or frequent gusts reach at least 35 miles per hour.
The blizzard watch indicates that forecasters believe these conditions may be met in coastal areas of southeastern New York and Connecticut as the storm strengthens and passes nearby on Tuesday in particular.
If the center of the storm hugs the coast, then a mix with or change to rain could occur along the coast, lowering snowfall amounts and making blizzard conditions less likely. This scenario looks less likely, though, compared to a more offshore track that would keep most coastal areas all snow.
The period of greatest concern in New York and Philadelphia is from Monday evening through Tuesday evening, though the storm could last into early Wednesday in New England.
For areas that stay all snow, well over a foot is likely to accumulate in what would be the heaviest snowstorm of the season for many. In fact, 2 feet of snow is not out of the question in a few spots, particularly across Long Island, parts of New Jersey, and in Massachusetts, depending on the exact storm track.
The storm is likely to be accompanied by small-scale, intense bands of snowfall falling at up to 4 inches per hour, and areas that experience these heavy "mesoscale" bands will see the highest snowfall totals. In addition, winds may gust higher than 45 miles per hour from the Virginia coast northward to Maine, and minor to moderate coastal flooding at the time of high tide is likely in many spots.
One reason why the snow will not accumulate to much more than 1 to 2 feet, despite the intensity of this storm, is that the low pressure area will move quickly northeastward, rather than slowing its forward speed and prolonging precipitation.