Plain-language summary:
Light to moderate snow will fall mostly along and northwest of the St. Lawrence River today, with the heaviest in the Laurentians. After a few snow showers along the cold front tonight, it will dry out and turn colder for Monday. A modest snowstorm will occur in southern areas, with less snow to the north, on Tuesday. Snow showers will occur along and northwest of the Appalachians Wednesday night before a snow squall ushers in very cold air Thursday into Friday. Snow is possible or likely next weekend, but how much is very uncertain. A fast-moving, cold weather pattern with frequent systems will likely continue into following week, though big storms appear less likely than originally thought.
Meteorological discussion:
Light to moderate snow along and northwest of St. Lawrence River today, heaviest in Laurentians, then brief shot of arctic air Monday
A low-pressure system located in the Great Lakes region today is bringing light to moderate snow to the region, mostly along and northwest of the St. Lawrence River, with the heaviest snow in the Laurentians (locally 6-8" or 15-20 cm possible) closer to the better dynamics and also with upslope enhancement. The storm is producing lighter precipitation than the widespread heavy snowfall in the Midwest U.S. yesterday, perhaps due to getting cut off from the Gulf of Mexico moisture. The system will quickly pass to the northeast tonight, with a brief shot of arctic air behind it for Monday and a few snow showers along the front before drying out, especially in the upslope areas of the northwestern Adirondacks and Eastern Townships of southeastern Quebec.
Moderate snow in southern areas, lighter snow to the north Tuesday
However, another broad but weak low-pressure system that is very elongated from north to south will already be approaching from the west. The strongest piece of energy will be near the southern end of this elongation, traveling through the lower Midwest U.S. and Ohio Valley by early Tuesday and eventually into southern New England by Tuesday night. The system will strengthen and consolidate as it moves offshore the U.S. East Coast, and with the cold air to the north of the storm, precipitation will fall as snow throughout the region. The heaviest snow will be from southern Vermont to southern Maine, where heavy snow of 6-10" (15-25 cm) is likely, with amounts tapering off to the north until almost nothing north of the U.S./Canada border. There is still some model disagreement, with ICON and GFS showing a stronger, snowier scenario and the CMC and ECMWF showing a weaker storm and almost nobody receiving >6" (15 cm). This is a missed opportunity for a widespread bigger snowstorm, like what occurred many times in December and January of last winter; if the disturbance had been a bit stronger and farther east, with a stronger northern disturbance and upper-level wave train to direct the storm more northward and allow it to strengthen more, there would be a widespread 10"+ (25+ cm) snowstorm that would extend farther north.
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| Source: TropicalTidbits |
Light snow along and northwest of Appalachians Wednesday night, very cold Thursday and Friday, another potential snow next weekend but uncertain how much
The fast-moving weather pattern will continue. An elongated Alberta clipper will produce snow showers Wednesday night along and northwest of the Appalachians, possibly enhanced by Lake Ontario in the St. Lawrence Valley and Laurentians, with a snow squall along its strong cold front ushering in a very cold arctic air mass on Thursday, by far the coldest of the season thus far, with the Laurentians going below 0F (-18C) Thursday night. Yet another system or two with a rather complicated setup will arrive next weekend, with at least one Alberta clipper as well as a southern, more moist system over the central or southern U.S. Depending on how the disturbances interact, we could just have an Alberta clipper with light snow, our region in a dry zone between the Alberta clipper to the north and the juicier southern system to the south, or the two could combine with a widespread bigger storm. This evolution will rinse and repeat to some degree the following week, but of course the details that can't be determined this far out will matter a lot in terms of sensible weather (e.g. whether we only see minor Alberta clippers or bigger storms).
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| Source: TropicalTidbits |
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| Source: TropicalTidbits |
Active weather pattern still likely afterward, but big storms perhaps less likely than earlier thought
The bigger storm scenarios appear less likely given the although the -EPO and -NAO is allowing a lot of arctic air to flood central and eastern North America over the next few weeks, the high-latitude blocking is not enough to allow for big meanders in the jet stream and a very amplified upper-level wave train. With the strong temperature gradient and jet stream, there will be many systems, but it might be more difficult for the northern polar jet (with the arctic air) and the southern jet (with the moisture) to combine and produce big snowstorms than originally thought a week ago. It appears that the upper-level trough might be a bit too flat and its axis centered right over our region instead of over the Midwest U.S., promoting systems to move more straight west to east instead of from southwest to northeast, in which case they could strengthen more and more importantly, gather Gulf of Mexico moisture. It is still way too early to rule anything out with such a volatile weather pattern, but ensembles do show below-average precipitation is more likely in the medium to long range. On the other hand, with the cold air and lack of Gulf of Mexico warmth and moisture, thaws are unlikely, allowing what precipitation that does occur fall as snow, often a dry, fluffy snow with cold temperatures associated with Alberta clippers occurring every 2 or 3 days. There are still a few model runs showing stronger upper-level troughs moving farther south into western North America in the long-range that would result in a storm ejecting into the Plains that can tap into at least some Gulf of Mexico moisture.
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| Source: TropicalTidbits |
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| Source: Climate Prediction Center |
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