Settle in: Paralyzing March blizzard set to slam Philly, New York and Boston


http://earth.nullschool.netComputer model projection of the blizzard on March 14, 2017.

So much for February’s spring-like temperatures.

A potent blizzard is gathering strength in the Midwest and Southeast, destined to combine into one major storm that will roar across the highly populated Washington to Boston corridor on Monday through early Wednesday.

The storm, unofficially named "Stella" by The Weather Channel, may dump a foot or more of snow on as many as 100 million people.

Winter storm and blizzard warnings are in effect in 13 states from Virginia to Maine, with the hardest-hit areas potentially picking up more than 2 feet of snow in less than 24 hours time.

By any standard, this storm is going to be the real deal. Strong winds? Check. Blinding, wind-driven snow? Yeah, it’ll have that. Coastal flooding? That too!

Image: weatherbell analytics

Forecast snowfall totals from the National Weather Service as of March 13, 2017.

The storm is likely to grind business in cities including Washington, D.C., Baltimore, Philadelphia, Newark, New York, Hartford, Providence and Boston to a halt on Tuesday, with virtually no air travel in or out of the region as well. Power outages are possible, and officials are urging people in affected areas to prepare for the storm ahead of time.

Wind gusts exceeding 50 miles per hour are expected from coastal New Jersey northward into Massachusetts, and this, combined with snowfall rates of 2 to 4 inches per hour, will lower visibility to near zero at times.

For this reason, blizzard warnings have been hoisted for areas from the New Jersey shore up to New York City and northeastward to Boston, including Providence.

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 warning indicates that forecasters believe these conditions will be met as the storm strengthens and passes nearby on Tuesday in particular.

Where will the jackpot be?

There are uncertainties in where exactly the heaviest snow will fall, but a foot or more is a good bet in Philadelphia, New York, and Boston, with blockbuster amounts of 2 or more feet to the northwest of these locations.

All of this snow will result from a rapidly intensifying low pressure area that will move off the Mid-Atlantic coast on Monday night, to a position near or southeast of Montauk, Long Island, by Tuesday evening.

The storm track is extremely important for where the heaviest bands of snow set up. If the low pressure area moves any closer to the coast than currently forecast, then snowfall totals in the big cities would be less than current estimates. Instead, there could be a mix with or changeover to sleet and rain for a time, as warmer air infiltrates the area from the Atlantic Ocean.

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 more of these heavy "mesoscale" bands will see the highest snowfall totals.

The most difficult place to forecast this event may be the Washington area, where marginally cold temperatures could keep the precipitation falling as rain, sleet or wet snow, rather than accumulating snow, and heavy bands of precipitation may or may not materialize.

The National Weather Service is calling for the season’s biggest snowfall event of the season there, but that’s not saying much, since the city’s received a measly 1.4 inches so far this season.

Jaded snow lovers in the nation’s capital are familiar with the so-called "D.C. snow hole," in which the city gets little-to-no snow while surrounding areas get clobbered. This may again happen this time around, in part because the storm will still be in its infancy as it passes near the city.

Image: weatherbell analytics

Simulation of satellite imagery on March 14, 2017, showing the major storm across the East Coast.

The key ingredients for this event include an Arctic high pressure system that is in position across southeastern Canada and northern New England. This will pump cold, dry air into the storm, helping to churn out the snow as Atlantic moisture flows into the area. Some cold temperature records were been set across New England this weekend as this 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, are now destined to meet up and combine forces to form a single, strong storm.

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.

One remarkable aspect of this storm will be its speed. This just isn’t your typical, lallygagging, lazy nor’easter. Blockbuster snowstorms in the Mid-Atlantic and Northeast tend to be long-lasting affairs, with snow falling for 30 hours or more. However, this one may feature a thump of heavy snow that falls during just 12 hours or less, with the ridiculously heavy snowfall rates more than making up for the time crunch.

3 terms to know

There are a few weather geek terms you’re likely to come across when following this blizzard on social media. First is bombogenesis, which is an actual meteorological term, and not a band name. It refers to a low-pressure area that sees an air pressure drop, or intensification rate, of more than 24 millibars in 24 hours. Typically, these "bombing out" storms are the most violent, and some of the biggest snow producers.

The second is a "dry slot," which sounds, well, a bit off-color, but refers to an area of dry air that gets entrained into a low pressure area at the mid-levels of the atmosphere. Forecasts call for such a phenomenon to affect eastern New England on Tuesday afternoon, which could limit snowfall amounts there since it would lead to lighter precipitation for a time.

And lastly, you’re likely to hear a lot about sleet. These are the little ice pellets that sting when they hit your face, and make a pinging sound on your windows. A mix with or changeover to sleet is anticipated for the immediate coast, possibly including New York City, on Tuesday as the storm center makes its closest pass. This will lead to slightly less snow there than in areas just outside the city.

Is this normal for March?

March snowstorms aren’t that unusual for the Mid-Atlantic and Northeast. In fact, Monday, March 13 is the anniversary of one of the most powerful storms to ever track up the East Coast, known as the "Superstorm of 1993." It dumped a foot or more of snow from Georgia to Maine, and knocked out power to tens of millions.

March blizzards have a history of hitting New York, too. A legendary blizzard struck the city on March 12, 1888, dumping 21 inches of snow.

The upcoming storm would come in as a top 10 snowstorm for New York if at least 18.1 inches accumulates in Central Park. In Boston, it’s been known to snow all the way into April.

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