Winter has been fickle these last few years for those of us who live in southcentral Alaska. The short days and long, dark nights arrive like clockwork but the cold and snow have been less than reliable. As the days shrink and frost sprouts on our windshields overnight, skiers, fatbikers and ice climbers are wondering if we’re in for another warm, snowless winter.
Just how the winter of 2016-2017 will play out is less than clear, but there is hope according to Rick Thoman, Climate Sciences and Services Manager of the National Weather Service Alaska Region.
“The dice was all loaded toward warm last year,” Thoman said. “We had what we knew was going to be a strong El Niño, we had very warm sea surface temperatures and we had low sea ice coverage in the fall. So, all of your big drivers were pointing the same direction.”
Indeed last winter was unusually warm and what little snowfall we had, disappeared quickly.
This year two of those three indicators are back: warm sea surface temperatures and low sea ice coverage. But La Niña, which occurs when colder sea surface temperatures occur in that region, has replaced the third, El Niño. Though far to the south, those sea surface temperatures extend their influence all the way to Alaska and could put a chill in the air that coastal Alaska hasn’t felt for the last few winters.
“It doesn’t necessarily mean it will be cold,” Thoman said. “But it certainly ups the chance for periods of cold weather during the course of the winter.”
Despite the potential for cold temperature intrusions, Thoman predicts a warmer than average winter in southcentral Alaska, though not as warm as last year.
The good news is that the cooling trend and periodic cold intrusions could mean more snow, both falling and sticking around.
“I would expect that since some cold periods are likely during the winter most low elevation places are going to wind up with more snow,” Thoman said. “Even if the precipitation is near normal, even below normal.”
He qualified that happy news with a warning that warm Chinook winds blowing out of the southeast can make quick work of thin snow cover but said, “there is probably less of risk of that this year.”
Beyond the coming winter, Thoman believes the trend for Alaska’s winters, at least in the coastal and southcentral regions, is more warm winters.
“The thing that’s worrisome, if you want winter for Alaska, is the very warm sea surface temperature,” he said. “They’re not just at the surface, this warmth extends to depth and that takes a long time to work its way out. And when you look at the very long time series of North Pacific sea surface temperatures, by some measures they are at the highest they’ve been since 1950.
“Global oceans are warming as well so the long term future for Alaska is really going to be dominated by those sea surface temperatures and they appear to be going, on the longer time scale, no where but up. The chickens have come home to roost.”
— Andy Hall