Winter in the Inland Northwest could be cold and snowy again if government scientists are right in an official winter outlook issued on Thursday.
The U.S. Climate Prediction Center is calling for a higher-than-normal chance of having the snow pile up in coming months.
If so, it will be a repeat of the snowier-than-normal conditions in three out of the past four winters.
But the slide into winter may be gradual. Experts said the worst of winter weather is likely to hold off until late December into March.
Driving the outlook is a pool of colder-than-normal water in the equatorial Pacific, a phenomenon known as La Niña.
La Niña is expected to cause the Northern Hemisphere storm track to shift northward and draw cold air southward out of Alaska and Canada.
The cold air could then mix with a flow of moist air off middle latitudes of the Pacific under a pattern typical of La Nina.
“The winter outlook this year is shaped by La Niña,” said Mike Halpert, deputy director of the Climate Prediction Center.
He cautioned that the outlook is really a three-month average of expected weather, but locales across the country “can expect a lot of variability” during the course of the winter season.
La Niña has been a fairly potent force in shaping winter weather in the Inland Northwest. In 2007-08, the city got 92.6 inches of snow at Spokane International Airport.
The following winter of 2008-09 brought borderline La Niña conditions. The snow kept falling, and falling until an all-time record of 97.8 inches of snow had piled up.
The average seasonal snowfall in Spokane is about 45 inches.
In 2009-10, an El Niño winter brought a meager 14.4 inches of snow.
El Niño is a warm-water phase in the equatorial Pacific and is known for bringing milder winter weather to the Inland Northwest.
La Niña rebounded last winter and brought 68.4 inches of snow to Spokane.
Ron Miller, meteorologist with the National Weather Service in Spokane, said that back-to-back La Niña winters often see greater snow in the second of the two.
Since 1950, there have been seven back-to-back La Niña winters. In five of those, the snowfall was greater in the second winter, including 2008-09.
“To say it’s going to be identical to last winter would be a mistake,” he said.
There are many factors that influence winter weather but La Niña is considered the strongest reliable indicator of the winter outlook.
Annual records support the likelihood of above-normal snow during a La Niña episode, he said.
As a result, ski areas should get their fair share of snow this year, Miller said.
Geography professor Bob Quinn of Eastern Washington University said he expects winter to ease in. The current round of slightly warmer-than-normal weather accompanied by rain at times should continue through the rest of autumn, he said
“We’ll eventually get snow, but it will be mid to late winter,” Quinn said.