Plain-language summary:
It will be quite mild and rainy through Monday, with most of the snow cover melting away. It will dry out but remain mild on Tuesday. A modest storm will bring rain changing to an elevation-sensitive snow Wednesday into Thursday, with the most snow at higher elevations and north of the U.S./Canada border. It then gradually turns colder but not extremely cold through next weekend, with some snow showers still possible, before a potential snowstorm early the following week. True arctic air dominates for the 2nd week of January, but it is uncertain if that will be accompanied by any snowstorm potential or if it will remain mostly dry.
Meteorological discussion:
Mild and rainy through Monday
North America is in the middle of an incredibly mild weather pattern with the strong, extended Pacific jet throwing mild, Pacific air into North America. Our region has escaped it for most of this week due to the remnants of the previous arctic air mass last week and a reinforcing shot of cold low-level air associated with a slow-moving surface high pressure in Quebec earlier this week. However, the surface high pressure has slowly moved eastward, and now a strengthening storm from the southwest is moving into the Great Lakes this evening, strengthening the southerly flow, with a band of rain in front of it moving from south to north across our region associated with the warm front. Once the last of the low-level cold pools have been mixed out, temperatures will reach 50F (10C) in most lower elevation locations by tonight or Monday morning, with most of the snow cover melting away. As the storm speeds into Quebec on Monday, a rather weak cold front will bring showers, though heavy rain appears unlikely due to the low-pressure center going well off to the north, taking the best dynamics with it, and areas like the Champlain Valley will get even less due to downsloping.
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| Source: TropicalTidbits |
Drier, but still mild for Tuesday, then rain changing to snow Wednesday into Thursday
By Monday night, the low-pressure system will have departed to the northeast, leaving drier and only slightly cooler conditions (still quite mild for this time of year). This lack of real cold air will be critical for the next storm poised to eject out of the Rockies on Monday, move rather slowly eastward through the Midwest U.S. and then eventually re-develop near Long Island on Wednesday. This is normally a rather favorable storm track for a snowstorm in our region, but temperatures in the lower 1000 m or so will be above freezing at the start of the storm, ensuring rain for everyone initially except the mountaintops. An initial band of heavier precipitation will advance from south to north, mostly rain south of the U.S./Canada border before turning to snow north of Montreal, especially over the Laurentians, early Wednesday morning. Then, as the storm slowly re-develops and strengthens along the New England coast, heavier rain will develop across New Hampshire and then move northward into Maine in the afternoon, with rain changing to snow in Maine. The storm
will manufacture its own cold air through upward motion and
precipitation, and cold air will also be gradually filtering in from the
west. Farther west, there will be only intermittent rain and snow showers until some more energy comes in from the west Wednesday evening, also coming with somewhat colder air. As such, rain will gradually change to snow generally from higher to lower elevations and from west to east until everyone changes over to snow by late Wednesday night. However, the storm will not be strengthening rapidly given the lack of strong temperature gradients, and the weather pattern is not blocked enough for the storm to stall out and produce snow for a long time. Instead, there may only be a 6-12 hour period for wet snow for lower elevations south of the U.S./Canada border, with the lowest elevations of the central and southern Champlain Valley perhaps not seeing any accumulation with warmer temperatures and downsloping off the Adirondacks. Northern Maine and southern Quebec are more likely to see substantial snow accumulations, with less rain at the start before a changeover to snow. Also, northwestern facing slopes of the Adirondacks, Green Mountains, and Quebec's Eastern Township hills will do quite well with upslope snow Monday night into Tuesday morning before the storm moves too far to the northeast later on Tuesday. The exact details and who gets how much snow will depend on the exact storm track and temperature profiles, which could still change a little as it is still 3-4 days out.
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| Source: TropicalTidbits |
Turning colder next weekend with a potential snowstorm early the following week
The storm will be strong and broad but slowly pull away on Wednesday and Thursday, leaving us with dry, colder northwesterly flow. This air mass from Canada is not especially cold since it takes time for the arctic air to filter back into North America after being scoured out this week. There may still be a subtle disturbance rotating around the storm in the northwesterly flow that could bring snow showers later next week, especially along and northwest of the Appalachians. Then, next weekend, a stronger system will eject out of the Rockies and move toward our region. With plenty of cold air in place, this could be a widespread snowstorm for our region for early the following week. The details are not known yet, and how much snow we see depends on if the system ends up being mostly in the polar jet stream, taking a farther north track that would imply less moisture and less snow, or if a disturbance in the southern jet stream can be strong enough in the southern U.S. to interact with the overall mid-latitude trough and energize the whole setup, bringing more moisture and forming a stronger storm farther south, tracking to perhaps near the mid-Atlantic U.S. or New England coastline, that would bring a bigger snowstorm, especially south of the U.S./Canada border. Another somewhat less likely but still possible scenario is everything being weak and suppressed to the south by a strong vertically stacked low across eastern Canada.
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