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Snow, cold, strong winds possible this weekend

Forecast models have come into much better agreement on the eventual track and intensity of a powerful storm system, which will develop from the Great Lakes off the Northeast Coast on Sunday. The track of the storm is quite unusual, with the surface low tracking from Southeast Canada to a position off the New Jersey Coast and eventually into the Gulf of Maine. A powerhouse mid and upper level low will amplify eastward from the Great Lakes, underneath Long Island, and eventually to a position just south and east of Cape Cod, aiding the strengthen an already powerful storm system.

The result will be the potential for snow from Sunday into Monday, with moderate snowfall accumulations and the potential for higher amounts farther east. But in addition to the snow will come strong, damaging wind potential as the system deepens offshore. Finally, behind the storm, a polar airmass will move southward — possibly the coldest in many years — and the coldest air of the season will sink into the area on Monday when temperatures may struggle to get out of the single digits.

The origin of the incoming system can be traced to the polar regions and Northern Canada. As it moves southward late this week into this weekend, the system will amplify — with a closed mid level low dropping south into the Great Lakes. Forecast models are in good agreement that the system will have a lot of energy involved with it in the mid levels of the atmosphere. But as it shifts south and southeast, it will encounter some resistance and begin to elongate eastward. The closed mid and upper level low will shift southeast through the Northeast States, and eventually to a position near or south of Long Island and eventually underneath Southern New England.

At the surface, this will translate to a low pressure system moving from Southeast Canada to a position off the coast of New Jersey and Long Island. As the storm moves northeast from there, it will begin to encounter tremendous mid and upper level atmospheric dynamic support. All forecast models agree that the storm will then rapidly deepen near Cape Cod to the Gulf of Maine. As this occurs, rapid cyclogenesis is expected with the development of a cold conveyor belt over Southern New England. For our area, it becomes a question of timing at this point.

GFS Model showing an tremendous upper level system south of New England on Sunday.

GFS Model showing an tremendous upper level system south of New England on Sunday.

The heaviest snows in association with the mature cyclone are likely to stay east and northeast of our area — over Southern New England. This means that our area is likely to avoid a blizzard and crippling snowfall. However, we have a slew of other issues to deal with. While this low pressure deepens offshore, models are in good agreement that bursts of moderate snow will move through the area on Sunday, with the potential for continued snowfall from an inverted trough. An inverted trough, at the risk of getting too technical, is an area  supportive lift for precipitation that extends well west from a main surface low. But they’re very difficult to forecast and models will struggle to pin down their location.

Our confidence is currently highest in 2-4″ of wind driven snow (we’ll get to the “wind driven” part in a moment) over New Jersey and New York City, with 4-8″ of snow possible over Eastern Long Island, Connecticut and areas into Southern New England. Higher amounts are possible if the inverted trough does in fact set up over the area — but confidence in its location and intensity are quite low at this time. One of the main stories moving forward from the snowfall — and hazardous conditions as a result of it — will be winds.

Forecast models have trended farther southwest with the entire mid and upper level atmospheric setup, and as a result have shown stronger low level winds tracking over the region as the cyclone deepens and strengthens. The GFS and ECMWF both agree that 925mb winds will exceed 60 knots for a period of time Sunday afternoon. With good mixing through the atmospheric column, these winds could mix down to the surface. Northwesterly wind gusts over 50 miles per hour are possible Sunday afternoon. This could cause significant blowing and drifting of snow as well as ground blizzard conditions at times.

GFS model showing the potential for gusts over 50-60 miles per hour Sunday afternoon.

GFS model showing the potential for gusts over 50-60 miles per hour Sunday afternoon.

The airmass behind the storm system will be borderline historically cold. Models indicate a high likelihood of mid and low level temperatures dropping to their lowest of the winter so far. The Euro, for instance, shows 850mb temperatures of -27C near the area on Monday morning. The result of this, with the snow cover in place and strong northwesterly winds, will be the potential for record-breaking cold. Most models, at this point, take New York City’s low temperature below 0 F on Monday morning.

In the area suburbs, readings well below zero show up on almost all forecast models. These airmasses can be tricky. Achieving below zero temperatures is not exactly an easy thing to do — and requires a unique set of conditions. But the pressure gradient between the departing storm, the tremendously cold airmass building in, and the wind direction and components on Monday morning argue that this may be the best chance for below zero readings our area will see this season.

NAM showing surface temperatures near or below zero on Monday morning.

NAM showing surface temperatures near or below zero on Monday morning.

While below 0 F temperatures are hard to achieve nowadays in New York City, surrounding areas will see widespread readings near or below zero without much doubt. The northwesterly winds will produce wind chills that may drop 20 degrees below zero or more on Monday morning. This kind of cold, and wind, can be dangerous to the health of those who are not adequately prepared.

Over the next few days, we encourage you to stay tuned for updates on all hazards including the snow, wind, and cold. This will likely be one of the most wintry weekends of the year.

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