Arctic air arrives, multiple wintry chances late week
Lets face it, the term “Polar Vortex” has become overused and oversaturated over the past few years. This time, however, it is certainly applicable: A piece of the polar vortex will be swinging southwards this week through New England, bringing with it extremely cold temperatures and an arctic airmass which is decidedly unusual for this time of year.
We spoke a few weeks ago about how the intrusion of this type of air was likely, due to the presence of a large ridge building from Alaska to the North Pole. The time has finally come, and the airmass over the Northeast US by the end of this week will feature temperatures 20 to 30 degrees below normal averages for this time of year.
Height anomalies (departure from normal) in the mid levels of the atmosphere show extremely cold air moving into the Northeast US by late week.
Forecast models suggest temperatures will fall into the single digits even in the Northern Mid Atlantic from late Thursday Night into Friday. Readings below zero are likely throughout New England and in the higher elevations from New York State to Vermont and New Hampshire. With the cold will come wind, and wind chill values are likely to drop below zero over a large majority of the Northeast US as well.
There will be a few chances for wintry weather accompanying the intrusion of polar air as well. First, a weak disturbances slides through the Northeast states late Tuesday into Wednesday. The low pressure center of this storm will track very far south — off the coast of the Carolinas. This occurs because the polar vortex is bearing down on the pattern — essentially squashing any chance of a storm moving up the coast.
The weak disturbance passing by will allow an area of light snow over the Northern Mid Atlantic and possibly parts of Southern New England — with light accumulations possible in some areas. Still, the overall impact of the event will be quite small — and the main story will be the arctic air moving in behind it.
A more significant system arrives late this week with the potential for wintry precipitation before a change to rain in the Northeast US.
The more significant storm system arrives late Friday into Saturday as a low pressure area begins forming to the southwest of the Northeast US. Ironically, the very cold polar air will already be on its way out, and the storm is likely to feature another tricky transition from snow, to mixed precipitation and eventually rain. The depth of cold in place before the storm is likely to at least support more wintry precipitation than the storm earlier today throughout the interior.
High pressure eventually slides offshore, and the winds around the high pressure will allow temperatures to warm with southerly winds, especially along the coast. Interior locations, however, are likely looking at another impactful event as wintry precipitation takes hold from Friday PM into Saturday AM ahead of any transition to rain.
Stay tuned over the next few days as we obtain more data and confidence with the storm moving forward. An initial map of impacts is available and included below.
