Plain-language summary:
A big rainstorm is gradually winding down through tonight,
with rain changing to a bit of wet snow in the higher elevations of the
Adirondacks. It clears out on Monday with the first freeze outside of urban
areas and large bodies of water occurring Monday night. However, it will turn
breezy and much warmer later in the week, with relatively clear skies
dominating south of the U.S./Canada but clouds and showers dominating to the
north after Wednesday. Next weekend and beyond will likely be dominated with a
much more changeable temperature pattern, with a stronger and more seasonable
temperature gradient and a faster-moving weather pattern.
Meteorological discussion:
The second big storm of the month is slowly weakening and
moving eastward, with steady rain tapering off to intermittent showers. Already
1.2-4” (30-100 mm) has fallen in southeastern Quebec and northern New England, except
in northern Maine, with less to the west. This distribution is typical for a Nor’easter
like this storm, and if it were the middle of winter, it would be a classic big
snowstorm over a large area. As colder air pours in, rain will change to wet snow
at high elevations (>1000 ft or 300 m) in the Adirondacks, with little or no
accumulation, but it will be just rain elsewhere, as the air mass is not particularly
cold. As high pressure builds in later Monday, skies will clear, setting the stage
for the first freeze for most locations away from urban areas, Lake Champlain,
and the Atlantic Ocean. This will be the record latest first freeze for these
locations.
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| Source: CoCoRaHS |
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| Source: TropicalTidbits |
The high pressure will quickly move offshore later in the
week, with strong southwesterly flow bringing unseasonably warm air into our
region, perhaps with highs at or above 70F (21C) south of the U.S./Canada border. Skies will likely be rather
clear through Thursday south of the U.S./Canada border, while areas to the
north will be closer to the frontal/baroclinic zone in northwestern Quebec and turn
cloudier starting Wednesday with showers possible or likely. A cold front will likely pass through
on Friday or Saturday, but it is unclear if the cool air will last or will get quickly deflected to the northwest again. If the temperature gradient happens to settle in our region, then we
will get more storminess and rain. This shift is due to a classic -PNA pattern
with a trough and cold air in western North America and a ridge and warm air in
eastern North America. The -NAO prevalent since July will neutralize, so the jet
stream will strengthen and the weather pattern will no longer be blocked or
very slow-moving.
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| Source: TropicalTidbits |
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