Though it’s been months since the Treasure Valley last saw snow, the memories of last year’s “Snowpocalypse” likely have not left most of us. Which is why the National Weather Service’s predictions for winter weather might make your blood run cold — and not just because temperatures will continue to dip.
The NWS and Climate Prediction Center on Thursday issued a La Niña advisory, explaining that the ocean-atmosphere phenomenon has between a 65 and 75 percent chance of continuing at least through winter 2017-2018.
“The consensus of forecasters is for the event to continue through approximately February-April 2018,” the report said.
A three-month outlook model shows the Treasure Valley in the predicted range for above-average temperatures and also above-average precipitation. La Niña winters generally cause a cooler, snowier season than average.
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Dave Groenert, lead forecaster with the Boise branch of the National Weather Service, said La Niña’s effect won’t take hold until December.
“November is kind of a wild card that’s not tied to La Niña,” Groenert explained.
And though long-term forecasts have Boise once again battling above-average precipitation, Groenert said that’s always subject to change. Storms often come in two- to four-week patterns that are difficult to predict so far in advance. And a general trend for the season doesn’t mean every day will be warmer or wetter than usual.
“Just because (the forecast) leans one way or another doesn’t mean we won’t be dry or cold at times,” Groenert said.
If winter weather patterns follow the CPC’s predictions, “it would speak well for the mountains getting more snow,” Groenert said. As for the valleys?
“It’s hard to say,” Groenert said.
Much of last year’s heavy snow came from cold-air inversions trapped in the valley that then turned incoming storms into snow events, Groenert said. That kind of happenstance is just too difficult to predict this far out (looking at you, Farmer’s Almanac).
Last year’s La Niña winter is also not a good indicator for what we’ll face in the coming months, according to Groenert.
“Statistically speaking, chances are we won’t see a winter worse than what we had last year,” he said. “If you were prepared for last year, you’ll be good this year.”