Cold and mostly dry through Monday; light to moderate snow Tuesday through Tuesday night; snow, ice, and rain likely Friday and another system likely next Sunday; potentially mild for a short time after but highly uncertain

Plain-language summary:

 

Cold and dry air through Monday, except flurries Monday evening from eastern Ontario to northern Vermont, will be followed by light to moderate snow Tuesday into Tuesday night, except for northern Maine. It will temporarily turn colder Wednesday before a likely warmer system brings snow, ice, and rain depending on location late Thursday into Friday. Another system is likely next Sunday but considerable uncertainty remains. A short-lived milder weather pattern could occur around New Year's Day, but uncertainty is even higher then. 

 

Meteorological discussion: 

 

Cold and dry air today into Monday, then light to moderate snow Tuesday into Tuesday night 

 

The weather pattern full of arctic cold across eastern North America has shifted substantially, with the retrogression of the upper-level ridge in Alaska to the Bering Sea allowing for an upper-level trough over the North American West Coast (-PNA) and +AO promoting a stout and persistent upper-level ridge in the central U.S. But with the core of the upper-level ridge well to the southwest of the region, arctic air just to the north over Canada still in abundant supply, and -NAO associated with eastern Greenland blocking pushing the jet stream just far enough south into New England, winter is still alive in our region. A clipper passing to the north over central Quebec brought light snow and a snow squall along the cold front to northern areas last night into this morning, but this afternoon, it is just dry with a shot of cold (perhaps not arctic) air into the region, except lingering snow showers in the mountains. However, another relatively weak and elongated disturbance will already be approaching from the Rockies and diving east and then southeastward Monday into Tuesday. Systems like this coming from the west and northwest typically do not bring much precipitation with limited moisture from that direction, though the strong temperature gradient will enhance dynamics with the warm advection, and there is just a little moisture coming from southern U.S. After a few flurries from eastern Ontario to northern Vermont Monday evening, this will result in a stripe of light to at times moderate snow across the region, except northern Maine which will be too far northeast of the low-pressure track. Models have been in surprising disagreement on the evolution of this system until this afternoon.

 

Source: TropicalTidbits

 

Another likely warmer system Friday, but a lot of uncertainty remains 

 

Colder air returns behind the system, but it will not be as cold with less southward penetration due to the central U.S. upper-level ridge strengthening further. Another system coming from the Pacific will eject from the northern Rockies and move east or southeastward into our region on Friday, likely farther north than Monday-Tuesday's system. This increases the likelihood for mixed precipitation or even rain south of the Montreal to Bangor line, with snow and ice more likely to the north. However, it will be several more days before specific details will be known with any confidence. Any cold shot behind this system will be very limited due to the upper-level ridge that is still very strong in the central U.S. with another system ejecting from the Rockies promoting warm advection again next weekend. That system would likely arrive in our region next Sunday and appears to track north of our region (though not a certainty yet), promoting either the heaviest precipitation to go to the north of our region, precipitation type to be mainly ice or rain, or both.

 

Source: TropicalTidbits

 

 

Source: TropicalTidbits

 

 

Possible short-lived milder period around New Year's Day, but tremendous uncertainty on specifics and any possible storms 

 

Over time, the axis of the central U.S. upper-level ridge will likely push farther east into the eastern U.S. around New Year's Day, which could allow more of the warmth to enter our region after a few days of relatively dry weather, though the ridge will likely be weakening. If the ridge is a little weaker, it could allow for the more traditional southwest to northeast storm track bringing wintry precipitation to our region, but if the ridge is stronger, it could just flood the region with milder air with periodic rain. There is tremendous run-to-run inconsistency and uncertainty in the long-range, enough so that even mere chances of storminess are hard to pin down. There are some signs of the AO turning at least neutral around that time, which could allow more of the arctic air to penetrate farther into the U.S. and render the thaw short-lived, but long-range ensembles indicate that the arctic air will likely still retain its focus in western Canada, with a little bit of southeast U.S. ridge providing resistance to southward penetration of cold air in the eastern U.S., though that could promote a stormier weather pattern in our region with more access to Gulf of Mexico or western Atlantic moisture.

 

Source: TropicalTidbits

 

 

Source: Climate Prediction Center