Alaskans and, really, the rest of the world can expect a La Niña climate pattern this winter.
That could mean a potentially cooler-than-average winter.
According to the National Weather Service Climate Prediction Center, there’s a 71 percent chance of a La Niña setting in by October. The center updated its forecast Friday from essentially a coin flip chance to now saying a La Niña is more likely than not.
What that means for Alaska is still unclear, National Weather Service climate researcher Brian Brettschneider said.
“It, historically, would generally mean cooler falls in Alaska and cooler winters. That hasn't worked out the last couple of times," Brettschneider said. "And so I like to say that it puts the thumb on the scale, but sometimes that thumb slips off the scale and it just doesn't work out.”
That’s not just because the Earth’s climate is warmer now than it used to be. A La Niña only accounts for some of the variability across an entire winter. Other things – like increased tropical cyclone activity, sea ice distribution or a polar vortex – can overwhelm that, Brettschneider said.
And even though La Niña winters tend to favor drier conditions, they sometimes produce more snow in Alaska.
“If you have the same amount of precipitation, but it's colder, then you get more snow," Brettschneider said. "You're converting more of the would-be rain into snow. And then also, generally, when it's colder, to a point, you get more efficient snow crystal production, and so you get fluffier snow.”
In Anchorage, one of the top three snowiest winters on record was a La Niña, while another was its counterpart El Niño, which tends to produce warmer, wetter winters.
And, Brettschneider said, the warmest winter on record in Alaska was during a La Niña. So the climate prediction can't say what will happen, only what is likely to happen, he said.
