Prolonged Chill Tightens Hold on the Great White North as America Sees Most Unseasonably Mild Christmas on Record.
An intense cold spell has seized a severe and lengthy Arctic outbreak, with temperatures hovering between -20C and -40C for weeks. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, its coldest December temperature in nearly five decades.
Consecutive Nights of Extreme Cold
Similarly, the communities of Mayo and Dawson experienced 16 consecutive nights dipping under the minus 40 Celsius threshold, with Mayo experiencing a low of -50.4C at the start of the week. Whitehorse also recorded a series of ten nights when the cold dipped under -30 Celsius.
This Arctic air mass pushed further southward during the holiday season. On Christmas Day, overnight temperatures in Edmonton fell below -28C.
Boxing Day was expected to bring readings no higher than -20 Celsius through a wide swath, encompassing cities from Edmonton to Quebec.
Expected to Continue For Days to Come
This harsh winter weather is expected to continue through the start of January. Officials have warned that the Yukon could face electricity outages soon, as its energy infrastructure faces unprecedented demand from historically high electricity consumption.
The prolonged chill has been caused by the polar vortex remaining anchored above Canadian territory through December, which funnels frigid northern air southward. Next week, the cold air mass is expected to retreat north gradually, enabling milder Pacific air to move across America and reach into portions of southern Canada.
Dramatic Difference to American Heat
In stark contrast, parts of the US experienced the hottest December 25th in their history as temperatures soared about 15-30C above the seasonal average. Across wide regions, the atmosphere was more akin to late spring rather than the end of December.
A number of states broke historical records for December 25th warmth. The capital of Oklahoma soared to 25C on Christmas Day, topping the prior high mark of 22 degrees established over forty years ago. Urban centers like Austin, Dallas, and Charlotte, North Carolina similarly saw thermometers rise past the 25C mark.
High-Pressure System Sustains High Temperatures
Above-average warmth is expected to continue through Boxing Day and the days ahead, with abnormal warmth projected to move through the American Southeast soon.
The warmth has been fuelled by a robust atmospheric ridge stretching from the southwestern deserts northward and eastward, establishing a classic heat-dome pattern. Such a configuration results in a widespread high-pressure system over a large portion of North America, effectively capping warm air at lower altitudes. Descending air compresses and adiabatically warms, fostering the buildup of exceptional warmth.
