A Sudden Stratospheric Warming could spark a "collapse of polar circulation", forecasters have said in a warning of an imminent "unusual" phenomenon.
Forecasts show the collapse will lead to a cold snap in the latter half of November, with cold weather and snow expected across the United States and Canada, then potentially Europe.
The Polar Vortex is described as the "keeper" of cold and, when strong, usually locks freezing temperatures into the polar regions.
But when it becomes disrupted or collapses, cold air can escape and winter weather follows.
PICTURED: A 3D simulation of the polar vortex over the North Pole, Canada and Europe
|SEVERE-WEATHER.EU/RECRETOS
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Such changes are known for bringing extensive snow and cold temperatures.
The infamous Beast from the East phenomenon in 2018, which saw the UK experience severe cold temperatures and chaotic snowfall, was caused by a similar Sudden Stratospheric Warming event.
Across the country, schools were closed, thousands of homes lost power, and there was widespread travel chaos and trains and flights were affected.
Normally, sudden stratospheric warming happens in the mid-to-late winter but this year, some meteorologists are predicting a particularly early event.
Sudden Stratospheric Warmings are known for bringing extensive snow and cold temperatures
|PA
In the past 70 years, stratospheric events such as this have only happened early a handful of times, and this year could be the earliest.
The change in pressure during the 30 days following a stratospheric warming event means the jet stream, which flows from the eastern United States across the North Atlantic and into Europe, will be weakened.
As a result, cold air from the Arctic could be released across America, Canada and Europe.
In particular, forecasters are predicting a strong release of polar air into the northern, central and eastern United States at the beginning of December.
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The infamous Beast from the East phenomenon in 2018 was caused by a similar Sudden Stratospheric Warming event
|PA
In Europe, a cold air anomaly is expected over the northern parts of the continent, potentially down into the UK as well if the low-pressure area continues south.
As December continues, the cold air anomaly is expected to spread into northwestern Canada, suggesting the northerly flow will remain stable.
This means cold air will continue to be pulled from the deep polar region down into the US.
As a result, the chances of a white Christmas across much of the US seems likely.
The Beast from the East caused travel chaos across the UK
|PA
PICTURED: The Met Office's temperature forecast for Friday this week
|MET OFFICE
More urgently, the Met Office has issued its forecast for the next two weeks.
Between Sunday, November 16 and Tuesday, November 25, "central and northern parts of the UK will likely be in a colder but drier regime than of late with overnight frost", it says.
It adds that showers may turn wintry on high ground in the north.
From November 26, to December 10, northern parts of the UK are expected to be colder than normal with "an enhanced risk of overnight frost", Met Office forecasts say.