La Niña releasing its less-than-icy grip over Northwest

The National Weather Service predicts a La Niña will exit soon, uncharacteristically leaving behind a puny snowpack in Oregon and Washington.

There is a 60% chance the Pacific Ocean along the equator will transition to normal temperatures by April, the service’s Climate Prediction Center said Feb. 12.

Below-average temperatures triggered the La Niña, normally linked to colder and wetter winters in the Pacific Northwest. This winter, however, has been more typical of a strong El Niño, triggered by warm seas.

For both Oregon and Washington, the two-month period of December to January was the warmest in 131 years of record-keeping, according to the National Centers for Environmental Information.

Washington’s snowpack is only 51% of average, according to the Natural Resources Conservation Service. Oregon’s is even smaller, 30% of normal.

It’s possible the snowpack could be even worse than in 2015, when it was only 16% of average on April 1, Oregon State Climatologist Larry O’Neill said

“It’s really unlikely we’ll get enough snow to recover from the poor snowpack,” he said. “One storm won’t do it. We will need a series of storms to get close to normal.”

December was the warmest on record for Oregon and Washington. The above-average temperatures persisted. Oregon had its fifth warmest January on record, while Washington had its 12th warmest. The climate center predicts February will be warmer than average, too.

Ironically, the “polar vortex” that froze much of the rest of the country contributed to the prolonged warm spell, O’Neill said. Cold air broke loose from the North Pole and blocked normal east-to-west weather patterns, keeping a high-pressure system to over the Northwest, he said.

While temperatures stayed warm in January, the rain, which battered the region in December, tapered off. January was the fifth-driest on record in Oregon, and the 22nd driest in Washington.

Even if snow starts falling at a normal rate, it won’t be enough to catch up, Washington Deputy State Climatologist Karin Bumbaco said.

“It’s not really looking good in terms of snow,” Bumbaco said Feb. 12 at a water-supply meeting hosted by the Washington Department of Ecology. “There is time for snowpack building, but I think we’re all pessimistic.”

Snowpack is vital for summer irrigation. For example, the Bureau of Reclamation’s five Yakima River basin reservoirs hold about 1 million acre feet of water, but the region needs another 1.5 million acre feet of water in the snowpack to fully supply irrigators.

Without more snow, some of the snow that does fall will melt into the ground rather than run into streams, NRCS hydrologist Matt Warbritton said. “Right now there is a lot of exposed ground,” he said.

Snowpacks in Idaho and California are slightly better, though still below normal. California’s snowpack was 60% of average on Feb. 12. In Idaho, the snowpack north of the Salmon River was 55% of normal, while the snowpack south of the river was 76% of average.