Arctic Blast Tightens Hold on Canada as US Records Most Unseasonably Mild Christmas in History.
An intense cold spell has seized an intense and prolonged cold spell, with temperatures hovering in the minus 20 to minus 40 Celsius range for weeks. This week, the Yukon community of Braeburn saw the mercury drop to -55.7C, marking its chilliest December reading in nearly five decades.
Prolonged Freeze Below -40C
Meanwhile, Mayo and Dawson endured 16 consecutive nights below -40C, with the temperature in Mayo bottoming out at -50.4 degrees Celsius on Monday. Whitehorse also recorded a series of ten nights when readings fell to minus 30 degrees or lower.
The deep freeze spread farther south over the festive period. In Edmonton, the Christmas overnight low dipped under -28 degrees Celsius.
Boxing Day was expected to bring lows of at least -20C across many regions, from Edmonton in the west to Quebec in the east.
Forecast to Persist into the New Year
This harsh winter weather is expected to continue through the start of January. Authorities have cautioned about potential power failures in the Yukon in the coming days, as the system endures record-high pressure from peak power usage levels.
This extended freeze is the result of a stationary polar vortex over Canada for much of December, allowing bitter Arctic air to spill south. The frigid dome is projected to gradually withdraw north gradually, enabling milder Pacific air to move across the US and into parts of southern Canada.
Dramatic Difference to American Heat
Conversely, sections of America recorded historically high temperatures for Christmas 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.
Multiple states established new Christmas temperature highs. Oklahoma City, Oklahoma, reached 25 degrees Celsius on Christmas, surpassing the previous peak of 22C set in 1982. Metropolitan areas such as Austin, Dallas, and Charlotte also logged readings above 25 degrees Celsius.
Heat-Dome Effect Fuels Warmth
Unseasonable heat is predicted to persist for the remainder of the week and beyond, with abnormal warmth projected to move into the south-eastern states later in the week.
The unseasonable temperatures are powered by a strong upper-level ridge reaching from the arid southwest across the continent, creating a heat-dome effect. Such a configuration results in a widespread high-pressure system blanketing a significant part of the landmass, effectively capping warm air at lower altitudes. Descending air compresses and adiabatically warms, allowing unusually warm temperatures to build.
