Arctic Blast Grips Canada as United States Experiences Most Unseasonably Mild Christmas Ever.
An intense cold spell has seized an intense and prolonged cold spell, with readings persisting between -20C and -40C for multiple weeks. On Tuesday, Braeburn in the Yukon recorded -55.7C, representing its most frigid December day since 1975.
Consecutive Nights of Extreme Cold
Similarly, the communities of Mayo and Dawson experienced 16 consecutive nights below -40C, with Mayo plunging to -50.4C on Monday. The capital, Whitehorse, likewise saw ten separate nights when readings fell to minus 30 degrees or lower.
This Arctic air mass pushed further southward over the festive period. Christmas night saw Edmonton's temperatures plummet below minus 28C.
Boxing Day was expected to bring minimum temperatures of at least minus 20C through a wide swath, including Edmonton, Montreal, Ottawa and Quebec.
Forecast to Persist Through Early January
The severe cold is forecast to persist through the start of January. Authorities have cautioned about potential power failures in the Yukon over the next several days, as its energy infrastructure faces unprecedented demand from record-high energy demand.
The prolonged chill has been caused by the polar vortex remaining anchored across the northern part of the continent this month, which funnels frigid northern air southward. Next week, the cold air mass is expected to retreat north allowing more temperate air from the Pacific to sweep across the United States and penetrate southern Canadian regions.
Pronounced Disparity with US Warmth
In stark contrast, parts of the US experienced historically high temperatures for Christmas as readings skyrocketed 15 to 30 degrees Celsius above normal. For numerous locations, the weather resembled a spring day in April or May than late December.
A number of states broke historical records for December 25th warmth. In Oklahoma, Oklahoma City hit 25C on Tuesday, exceeding the old record of 22C from 1982. Cities including Austin and Dallas, in Texas, and Charlotte, North Carolina similarly saw thermometers rise past the 25C mark.
Atmospheric Ridge Sustains High Temperatures
Above-average warmth is expected to continue through Boxing Day and the days ahead, with abnormal warmth projected to move into the south-eastern states later in the week.
The unseasonable temperatures are powered by a robust atmospheric ridge reaching from the arid southwest across the continent, establishing a classic heat-dome pattern. This pattern establishes a broad area of high pressure over a large portion of North America, trapping warm air near the surface. As air sinks through the atmosphere, it compresses and heats further, enabling abnormally high temperatures to develop.
