The temperature in Alaska’s largest city officially hit 42 degrees – four degrees shy of a record – on Tuesday as the seemingly “new normal” of the 2010s – abandoned in 2021 – returned to Anchorage.
First came Chinook winds that toppled trees along the Chugach Mountain foothills above the city, and rains that left streets flooded in places between the icy berms of snow left from a very wintery December.
Blame yet again a throbbing polar vortex that has been stretching and retracting as it swirls the winds around the northern half of the globe. Polar vortex (PV) and Arctic Oscillation guru Judah Cohen at the consultancy Atmospheric and Environmental Research (AER) has counted five stretched PVs so far this year.
“The fifth stretched PV since Jan. `1 is well underway and will drag the cold air in Canada and the Western U.S. into the Eastern U.S. by the end of the week with one or possibly two chances of snow,” he blogged Wednesday. “But as has been the case all winter, as long as the PV remains strong, the cold and snow is ephemeral and will last for only a few days and milder temperatures quickly return, so the weather roller coaster continues.”
Coastal Alaskans are now well familiar with that rollercoaster that has left them either shoveling too much snow or sliding around skating rink-like streets after the winter rains.
If it makes Alaskans feel any better, Cohen, whose forecasts focus on the lower-48, notes that it isn’t just the north that has witnessed this sort of cycling.
“The theme of this winter has been ‘lather, rinse, repeat’ in the Eastern U.S. in sync with a circular followed by an elongated or stretched PV and then the whole cycle repeats on a continuous loop,” he wrote. “This late into the winter I see no compelling reason to anticipate a cessation of the cycle but my understanding of what is fully going on with the circulation is limited.,,,(But) this whole cycle will eventually end if vertical wave energy is absorbed in the stratosphere instead of being reflected and/or the final warming occurs.”
The “final warming” would be what most people simply consider the end of the snowy season or summer in Alaska. The 49th state really doesn’t have much of what the rest of the country would consider spring.
Spring in Alaska is the season when the opportunity for cross-snow travel brings out snowmachine riders, fat-tired cyclists and skiers in droves to take advantage of what they call “the crust.”
The crust can basically be described as snow that goes from ice-road to mush on a daily basis as weather patterns traditionally shift to clearer skies bringing warmer days and colder nights.
Monthly precipitation drops steadily in the Southcentral part of the state from February to April. April is the driest month in Anchorage with an average half-inch of precipitation, about a sixth the amount of the usual August, according to the National Weather Service.
That pattern has not changed much as the state’s urban core – about half of all Alaskans live in the Anchorage Metropolitan area – has experienced a string of unusually warm winters. Overall, the state’s nine warmest years have some since 1980 with 2019 leading the way, and winter warming has largely driven the change.
Something of a cool down started in 2020, and 2021 was about as normal as normal ever gets in Alaska. Since then, however, despite early predictions for cooler weather this winter, the state has resorted to the pattern of the 2010s.
Since the start of 2021, Anchorage’s temperature is running 4.5 degrees above normal as of Wednesday, according to the National Weather Service, and this despite sea ice back to near historic levels in the Bering Sea upwind to the west or, more accurately, sometimes upwind to the west.
Though the winds that affect Alaska weather come from generally the west as the planet spins east to west on its axis it hurtles through space, they seldom come directly from the west. Ridges of high-pressure air in the atmosphere instead steer the winds around much the way mountain passes do at lower elevations.
Both ice cover and sea surface temperatures tend to play a major role in how these ridges develop, and the ridges can set up to bring frigid Arctic air roaring into the Anchorage from the northwest over the polar ice cap as happened in December or warm tropical air surging up from the south Pacific as is happening now.
If one of the weather models is right – always a considerable if – Cohen reports that an “impressive” ridge of high-pressure air could soon develop in the Gulf of Alaska, forcing the east-moving jet stream to the south to pick up warm tropical area before bending northward again into the 49th state’s urban underbelly.
“It should result in highly anomalous weather, if nothing else some unseasonable warm temperatures to Alaska,” he wrote. “But what about cold temperatures downstream?
“The predicted southwest to northeast tilt of the ridge suggests to me more of a Rex block (high pressure to the north with low pressure to the south), which would then favor cold temperatures across Southwest Canada and the Northwestern US. But the ridge could take on more of a full longitude ridge favoring cold temperatures east of the Rockies and eventually the whole Alaskan block can cut off from the jet stream becoming an island onto itself with zonal flow to the south and the US turns mild coast-to-coast.”
Who knows? But clearly what happens in Alaskas doesn’t stay in Alaska.
And no matter how weird the warm weather in Anchorage might seem now, it is worth keeping in mind the weather in Anchorage has long been weird.
What was once the biggest sled dog race in the state, the Anchorage Fur Rendezvous Open World Championship, is set to hit the roads and trails of the city Friday, Saturday and Sunday, and it has been periodically run in slushy conditions since the 1960s.
The 1961 Rondy “Doug Mushers’ Annual” has a photo of 1960 Rondy winner – the late Cui Bifelt from Huslia to the north of Yukon River – standing jacketless with his bare hand on the handlebar of his sled on a rain-soaked Fourth Avenue in downtown Anchorage.
Weather records show the temperature hitting 41 degrees on Feb. 22 of that year. Annual variability in Alaska has always been large and that has not changed as the average annual temperature of the globe has crept ever higher since the last Ice Age.