Prolonged Chill Tightens Hold on Canada as America Sees Hottest Christmas Ever.
A prolonged deep freeze has enveloped a severe and lengthy Arctic outbreak, with temperatures hovering from 20 to 40 degrees below zero for multiple weeks. This week, the Yukon community of Braeburn saw the mercury drop to -55.7C, its coldest December temperature since 1975.
Prolonged Freeze in the Deep Minus Forties
Similarly, the communities of Mayo and Dawson experienced sixteen nights in a row below -40C, with the temperature in Mayo bottoming out at -50.4 degrees Celsius at the start of the week. Whitehorse similarly reported ten separate nights when temperatures dropped below -30C.
The bitter chill extended its reach south over the festive period. In Edmonton, the Christmas overnight low dipped under -28 degrees Celsius.
The day after Christmas was forecast to deliver minimum temperatures of at least minus 20C in numerous areas, including Edmonton, Montreal, Ottawa and Quebec.
Expected to Continue into the New Year
The frigid conditions are predicted to linger through the start of January. Authorities have cautioned about potential power failures in the Yukon soon, as the system endures record-high pressure from historically high electricity consumption.
The prolonged chill has been caused by the polar vortex remaining anchored above Canadian territory through December, enabling a surge of icy Arctic winds to descend. Next week, the cold air mass is expected to retreat north gradually, enabling milder Pacific air to move across the United States and penetrate southern Canadian regions.
Dramatic Difference Compared to Stateside Temperatures
In stark contrast, parts of the US experienced their warmest Christmas Day on record 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. In Oklahoma, Oklahoma City hit 25C on Tuesday, surpassing the previous peak of 22C set in 1982. Urban centers like Austin, Dallas, and Charlotte, North Carolina were also among those that recorded temperatures above 25C.
High-Pressure System Drives the Heat
Warmer-than-normal conditions are forecast to last on December 26th and into the weekend, with unseasonable heat forecast to sweep across the southeastern US in the coming days.
The warmth has been fuelled by a powerful high-altitude ridge extending from the desert south-west towards the north and east, which generates a heat-dome phenomenon. This setup creates an extensive zone of high atmospheric pressure blanketing a significant part of the landmass, effectively capping warm air at lower altitudes. Descending air compresses and adiabatically warms, enabling abnormally high temperatures to develop.