Those unusually high temperatures in Whitehorse during the first half of December?
The warm air that lifted Whitehorse’s daytime highs well above freezing, melting snow and creating a slippery mess on the city’s sidewalks, originated in the area around the Pacific archipelago, an Environment Canada meteorologist said.
“The biggest story so far is just that it’s been so incredibly warm in Yukon for the first half of the month…. Looking back at the statistics, it was well above zero in Whitehorse for many days this month already, which is very unusual. It’s incredible,” said Doug Lundquist, the warning preparedness meteorologist for the B.C. interior and Yukon.
“We got a subtropical flow, so the air in Yukon was originating more down around Hawaii and the subtropics and although it wasn’t as warm as there, a lot of that warmth (was) surfacing in the Yukon.”
The warm air also got a helping hand from a ridge of high pressure that parked itself over western Canada, trapping the warmth and preventing cold air from moving back in.
“It was those two things, that warm origination of the air and this ridge of high pressure that blocked the pattern,” Lundquist said.
As a result, he said, temperatures were, on average, about 3.4 C higher than usual for this time of year in Whitehorse. In fact, the city even broke a daily historical record high — on Dec. 6, Whitehorse hit 5.9 C, the warmest temperature recorded for that day since at least 1900. It’s also a far cry from this time last year, when the high was -19.6 C, and 2015, when the high was -8.2 C – the second-warmest Dec. 6 in the past five years.
Eight other days this month, while not record-breaking, were the warmest recorded since at least 2009. By contrast, for the same period last year, the recorded highs were well into the negative teens and low 20s.
“It’s incredibly above normal and there’s only been a few millimeters of precipitation, which is fairly low for this time of year, so this is extraordinarily warm weather,” Lundquist said. The relative dryness makes it distinct from what’s colloquially known as a “Pineapple Express,” he added, which, although also originating from Hawaii, brings with it heavy precipitation.
As Whitehorse residents have probably noticed by now, though, the warmth appears to have moved on, plunging the city back into more seasonal temperatures.
“The upcoming weather for the next couple of weeks will probably be closer to the usual,” Lundquist said.
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