Plain-language summary:
Snow showers and squalls today will
end tonight, with a colder air mass following it. Monday and Monday night will
be the coldest day of February so far with clear skies, before it turns milder
again while staying dry through Thursday, though it will turn cloudier by
Thursday. There is a potential for a snowstorm in interior New England on
Friday, but it is too early to tell, and marginal temperatures might limit snow
accumulations to interior areas and cause the snow to be wet. It will turn cold
next weekend, and then likely milder the following week, a big change from
previous long-range forecasts.
Meteorological discussion:
With snow and cold having returned
this week, we finally have a decent snow cover over most or all of our region. For
one of the few times this winter, a ridge has built in western North America
and extended all the way to Alaska, with a deep trough over eastern Canada and northern
New England. While characteristic of recent winters, the pieces still failed to
come together for a truly big Nor’easter, a clipper diving southeastward into
Quebec today will set off snow showers and squalls in northern New England tonight,
especially on western facing slopes. While it will temporarily turn slightly
milder with the southwesterly flow south of the clipper, it will still be cold
compared to the unseasonably warm Great Lakes, and a lake-effect snow band will
get going off Lake Ontario over northwestern New York due to the southwesterly
flow. Localized accumulations of 8” (20 cm) are possible, limited by the
movement of the band north and then south as the clipper passes to the north. In
northern New England, most areas will see <1” (2 cm) except in higher
terrain, as the best dynamics stay north of the U.S./Canada border. Eastern
Ontario and the Laurentians north of the St. Lawrence River will see steadier
snow with better dynamics with up to 2-4” (5-10 cm) total. The clipper’s cold
front could bring a final snow squall, though models are not indicating for it
to be particularly strong or penetrate southeast of the Appalachians, where
little or no snow will fall due to downsloping. Due to the cold temperatures, the snow will be fluffy, with higher snow to liquid ratios than the 10:1 indicated in the map below.
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| Source: TropicalTidbits |
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| Source: TropicalTidbits |
Cold surface high pressure will move
in from northern Ontario on Monday, with it being sunny and dry for most, and
clear skies Monday night will lead to the coldest night we have seen this month,
though it will not be that much colder than average. The high pressure will already
move east by Tuesday, allowing southerly flow to gradually warm the region up
through Thursday, with upper-level ridging quickly building over our region. It will stay dry, with daytime temperatures reaching well
above freezing for most of the region by Thursday, allowing some melting of the
snow cover. It will turn cloudier by Thursday as the next low pressure system
approaches from the west.
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| Source: TropicalTidbits |
By Thursday and Friday, a trough will dive
southward from central Canada into the eastern U.S., while a southern storm
with more moisture will eject into the central Plains. If the trough can dive
southwestward enough to capture the southern storm on the eastern side of the
trough, making the trough negatively tilted and causing the southern storm to
move northeastward and strengthen quickly, we would have a big snowstorm for
interior New England for Friday into early Saturday. However, latest models show the two features phasing too late and too far north for a significant snowstorm in our region, and given the lack of
such events in recent years, I am inclined to believe this solution. The cold air will also be scoured
out ahead of the storm, and we will have to rely on the deepening trough to
bring in cold air soon enough, as the storm comes in, which means temperatures
will likely be marginal, making snow less likely for coastal areas and any snow
that does fall to be wet. A rainier outcome is also possible if the northern
system is stronger and pulls more warm air in. It is too far out to tell what
outcome will occur, with it being sensitive to subtle differences in location
and intensity of the pieces. As is often the case in these types of setups, Maine is the most likely to get a snowstorm, since the systems would have more time to phase and strengthen by then, and there is more cold air there
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