Bizarre coastal storm to bring snow and ice pellets to Maine and prevent a torch; weakening storm to provide light rain, ice, or snow mid-week; wintry next 2 weeks with possible/likely snowstorm for many late week

Plain-language summary:

A bizarre offshore storm will being snow and ice pellets to Maine tonight through Monday night but keep areas farther west dry. After a cold night tonight northwest of the Appalachians, it will be rather mild for most of this upcoming week but without a real torch. Some light rain, ice, or snow is possible Tuesday night through Wednesday evening, especially in eastern Ontario. A more significant snowstorm is likely Thursday evening through Friday evening. Overall, the next 2 weeks will likely be stormy and it will gradually turn colder as well though not especially cold.

Meteorological discussion:

A bizarre storm offshore will obtain some subtropical characteristics as it meanders in the Gulf Stream, which is quite rare for January but a testament to the anomalously warm waters there. Due to very weak winds aloft, it will only slowly move east and then north, interacting with and rotating around a weaker low pressure to the northwest, leading to intermittent bursts of precipitation emanating from the storm which will mostly affect Maine. Only spotty light precipitation will occur farther west due to the storm moving far to the east into New Brunswick. The same upper-level pattern that led to weak winds aloft and producing the cut-off low also removed most of what little cold air there was aloft, which means that snow will turn to ice pellets over Maine late tonight, despite an otherwise perfect storm track for snow, before changing back to snow tomorrow night before ending as dynamic cooling from ascent and melting of snowflakes cools it down aloft. Up to 4" (10 cm) of a dense snow and ice pellets mixture is expected in Maine.

Source: TropicalTidbits

However, more persistent northerly winds at the low-levels have transported low-level cold air since Friday, and combined with new snow cover from Friday's storm, is leading to some of the coldest surface temperatures of the winter so far north and west of the Appalachians. It is warmer southeast of the Appalachians due to some downsloping flow and lack of snow cover. With temperatures warming aloft, weak sunshine in January, and snow cover, the low-level cold air is now trapped underneath a strong inversion and is pooling in the St. Lawrence and Champlain Valleys, where some locations where the skies remain clear will drop to 0F (-18C) or lower tonight.

 

Source: Aviation Weather Center

 

Source: PivotalWeather

 

 

The slowly-moving, bizarre coastal storm will maintain the northerly low-level winds that will be only briefly interrupted on Wednesday as a system moves in from the northern Great Lakes. This will prevent another big warmup that is occurring over the central and southern U.S. from pushing into northern New England on north, though it will still turn milder with above-average temperatures for January. The Great Lakes system will be weakening as it moves in, but could bring some intermittent light precipitation from Vermont on westward Tuesday night through Wednesday evening. The greatest precipitation will be over eastern Ontario. Precipitation type will be tricky as temperatures aloft will be just above freezing initially but any precipitation will cool down the atmospheric column through evaporative cooling and likely lead to a changeover to snow except for the southern Adirondacks and southern Vermont. However, low-level temperatures will warm during the day Wednesday as weak southerly or westerly winds mix out the inversion somewhat and could lead to a brief change to rain south of the U.S./Canada border, before modestly colder air moves back in with winds turning to the northwest again Wednesday night. Any lingering showers will change to snow showers and end overnight.

 

Source: PivotalWeather

A "cold" high pressure briefly approaches but stays to the north for Thursday. "Cold" high pressure is by this year's standards though -- the air mass up there will likely be warmer than average but cold enough to make the storm following right behind wintry. From Thursday night into Friday evening, there is decent multi-model and ensemble support for a significant snowstorm for northern New England, northern New York, eastern Ontario, and southern Quebec. Characteristic of this winter, temperatures will not be all that cold all the way up to 800 hPa but they appear to be just cold enough for snow barring a significant strengthening or northward shift of the storm. The storm will initially cut into the Great Lakes but a cold high pressure over central/northern Quebec should keep the cold air in and force coastal redevelopment, thwarting any warm surge. That said, it is still 4-5 days away, and I would not be surprised if it ends up tracking just a little farther north, especially compared to what the GFS model shows, given the lack of true arctic suppression and the way this winter has gone so far.

 

Source: PivotalWeather

 

 

Source: PivotalWeather

There appears to be another winter storm chance around the 23rd or 24th but the models are in such large disagreement on it that anything from a miss to a rainstorm is possible for now. However, it appears clear that the weather pattern over the next 2 weeks will be much more wintry than the period surrounding New Year's Day. With the Pacific jet stream weakening, Arctic air will finally be able to gradually engulf most of Canada likely by next weekend or so. The clash of Arctic air with the much warmer and more moist air to the southeast due to a resilient southeast U.S. ridge typical of La Niñas, it looks to be a stormy period, with a lot of all different precipitation types possible, but probably not predominantly rain like it has been so far this month south of the U.S./Canada border. It is also looking colder but still not especially cold with the core of the cold expected to stay to the northwest due to the southeast U.S. ridge holding some ground.

Source: TropicalTidbits