If current trends continue, the eastern half of the US is in for one extraordinary winter.
Just last week, a strong late-fall Arctic warming flushed chill air out over the Great Lakes, setting off a lake effect snowstorm in Buffalo that buried the city in one year’s worth of snowfall in just two days.
This week’s extreme weather prelude brought a major warm snap that set off rainfall, sent temperatures surging to 62 degrees in Buffalo and pushed rivers in the area above flood stage. An odd northward hot air surge ahead of the next blow. One that will be fueled by a similar, out of the ordinary, Arctic heat-up that is predicted to fling a freakish Thanksgiving snowstorm at the US East Coast on Wednesday.
(Maximum snowfall potentials for the predicted Thanksgiving Snowstorm as provided by the National Weather Service.)
A storm that may dump more than a foot of snow along a swath from Virginia to Maine and set off blizzard-like conditions as a low pressure rapidly intensifies in a raging storm track torching away off the New England Coast.
Such major predicted and potential snowfall amounts are more reminiscent of a significant January event than what is typically seen for a Thanksgiving period which usually features cold placidity. But this Thanksgiving is predicted to be anything but placid as coastal gales and record-challenging snowfalls are likely to sock holidayers in and generate travel snarls throughout the Mid Atlantic and Northeast.
(Planetary wave pattern over Eastern US with intensified storm track in association with predicted strong winter storm for Thanksgiving in the Wednesday GFS model run. Image source: Climate Reanalyzer.)
The spurs to this most recent Arctic invasion are two high amplitude Jet Stream Waves — one over Alaska and one near Svalbard. Together, these upper level flows are pulling yet more warm air into an already warmer than normal Arctic. These invasions coincide with yet another form of upper level warming — Sudden Stratosphere Warming (SSW). A kind of warm air catapult up from the troposphere and into the Arctic from over the Asian Continent.
A combined set of conditions that is generating a baked atmospheric cake set of warming for the Arctic and driving the southern edge of the polar vortex southward over the Eastern US.
Overall, Arctic heat anomalies are expected to spike as high as 3.5 C above the already hotter than normal 1979 to 2000 average by the wee hours of Sunday morning this week. A very strong warm departure for November even in the current age of human-driven climate change and polar heat amplification.
(Very strong early season polar warming and amplification during late November shoves cold air out over North America and Eastern Asia in the GFS model run. Note that average temperatures in this measure are based on the already warmer than normal 1979-2000 period. Image source: Climate Reanalyzer.)
Last year, similar events drove cold air invasions through the Eastern half of the US and greatly intensified the North Atlantic storm track. As a result, the UK experienced its stormiest winter on record. This year, warm waters in the equatorial Pacific and off the US East Coast may well keep the storm track oriented along the Gulf Stream. This would result in much stronger events for the Eastern US and potentially quite powerful Nor’easter type coastal storms should the current pattern persist.