Plain-language summary:
The current cold snap will be ending
tomorrow, with some snow accompanying the warming trend Tuesday evening into
Wednesday, before turning even milder with rain for most on Thursday and Friday,
except possible ice and wet snow in Quebec and northern Maine. It turns
slightly cooler next weekend but still mild by January standards. A potential
storm could bring snow next Sunday or the following Monday, with the relatively
mild air still being cold enough for snow, but it could also miss to the south.
It appears relatively dry afterward through February 5, without any
particularly warm or cold air masses.
Meteorological discussion:
The coldest air of the season, still
not exceptionally cold, is over us this weekend, with many locations reaching
near or below 0F (-18C) tonight with clearing skies, though winds might be a
bit too strong for it to get that cold in the wider St. Lawrence and Champlain
Valleys. The cold air will be retreating northeastward tomorrow as the cold
high pressure shifts from the Midwest U.S. to the western Atlantic, allowing winds
to shift to southwesterly. However, given the chill we just had and the now widespread
snow cover extending all the way down to the Ohio Valley and mid-Atlantic U.S.,
it will take some time for truly warm air to be able to reach our region. There
will be some resistance initially, with a weak backdoor cold front bringing
some snow showers Monday evening, especially in northwestern New York, which
will see upslope enhancement, and north of the U.S./Canada border. The front
will briefly push colder air back into the region for Tuesday. A weak disturbance,
not even a closed low-pressure system, moving east into the Great Lakes region
will induce warm advection snow over our region Tuesday night into Wednesday,
with up to 4” (10 cm) possible in some spots. For now, it appears that the most
snow will fall from eastern Ontario east-southeastward to southern Maine, with
it staying mostly dry in central Quebec and northern Maine.
After that disturbance goes by, warm
advection will continue, and one or two more weak disturbances, will move
northeastward into the Great Lakes and then into southern Quebec, farther north
than the first one. With the cold air already scoured out by this point, and
the storm tracking so far north, precipitation will be primarily rain, especially
south of the U.S./Canada border. There could be freezing rain and wet snow in
northern Maine and Quebec, where it will be a little colder, especially if the
low pressure ends up tracking a little farther south, which would allow slightly
colder air from a new high pressure in northern Quebec to come just in time for
the storm.
Slightly cooler air follows that
storm, but it will still be mild, with central Canadian ridging being quite
strong, cutting off true arctic air. However, this being late January, it will
probably be cold enough to snow if any storm from the southern U.S. were to
reach New England. There is a possibility of a Nor’easter next Sunday into the
following Monday that would bring a sizeable snowstorm in our region. Like the
entire winter so far, the lack of a deep, neutrally or negatively tilted trough
over the eastern U.S. will likely preclude a rapidly intensifying Nor’easter
that would bring feet of snow. The central Canadian ridge, with the associated
northwesterly flow in the eastern U.S., could also just suppress any storm to
the south, like most models currently show, but it is too early to tell for
sure.
After that, it still looks mostly mild, with
arctic air staying to the north due to the positive NAO and AO, though the trough over Atlantic Canada may
allow colder air to sneak southward into our region occasionally, unlike the
rest of the U.S. and southern Canada. The central Canadian ridging will promote
deep northwesterly flow in our area, cutting off Gulf of Mexico moisture, with
a lack of big storms. A couple of Alberta clippers could bring light snow to
areas west and northwest of the Appalachians, but any bigger storm will
probably have to wait until after February 5 or so.
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