Plain-language summary:
After near-record high pressure brought the coldest night of the season so far last night, it will quickly warm up through Tuesday, with a little snow or mixed precipitation late tonight into early Monday morning from the Adirondacks into southern New Hampshire, and then a thaw and rain on Tuesday. It will gradually turn colder afterward, with a little snow at least at mid to higher elevations and perhaps mixed precipitation at lower elevations likely on Wednesday into Wednesday night and snow of uncertain magnitude next weekend. It will likely turn very cold immediately afterward before turning milder between Christmas and New Year's Day.
Meteorological discussion:
Last night was the coldest night of the season thus far with a very strong and cold high-pressure system (near record-high pressure) overhead. As the high pressure moves off to the east, the cold air will modify with wind switching to southeasterly. A weakening disturbance will bring a little snow (and possibly rain or freezing rain in a few spots) to the Adirondacks into southern New Hampshire late tonight into early Monday morning, but any accumulation will be light as most of the moisture stays to the southwest. A stronger storm will move into northern Quebec on Tuesday, bringing strong, warm southerly flow, a thaw, and rain to the entire region. Rainfall will be lighter in the Champlain Valley due to the downsloping southerly flow.
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| Source: TropicalTidbits |
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| Source: TropicalTidbits |
However, due to a building western North American ridge (+PNA), a trough will build over eastern North America later next week, so the thaw will not last. The storm's cold front will pass through and bring somewhat cooler, but still mild air for Wednesday. Meanwhile, a rather weak disturbance will eject out of the Rockies, though the timing is a little uncertain still. The disturbance will move quickly east-northeastward and strengthen slightly and likely will bring some snow at least at mid to high elevation areas, with rain possibly mixing in at lower elevations due to the lack of antecedent cold air. The lack of antecedent cold air and weakness of the disturbance will most likely preclude substantial snow accumulations. After that moves out on Thursday, an arctic air mass will bleed in to some degree, but will be halted by another disturbance. The disturbance will be accompanied by a digging upper-level trough that if oriented negatively tilted and can pull any more moisture-laden system in the southern U.S. northward, a big snowstorm would result over our region. However, models and their ensembles appear to show the trough not digging as much and too far east compared to a few days ago, with any southern disturbance too far away to interact with, leading to just a moisture-starved clipper with light snow over our region. It is still a week away, so things could still change.
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