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Weather and Climate

Neutral Weather Pattern Sets Up 'Anything Goes' Northwest Winter

What kind of weather might the Northwest be in for this fall and winter? Well, one meaningful clue came when federal forecasters at the National Weather Service Climate Prediction Center Thursday dropped their "La Niña Watch.”

La Niña and its opposite, El Niño, are tropical climate patterns that can strongly influence snowfall and temperatures in the Pacific Northwest. La Niña is characterized by unusually cold surface waters in the equatorial Pacific Ocean.

For much of this year, federal forecasters thought a mild La Niña was developing. But no longer. Kathie Dello, deputy director of the Oregon Climate Service at Oregon State University, said the outlook has now been dialed back to “ENSO neutral” in weather-speak -- or La Nada.

But she said that doesn't necessarily equate to an "average" winter.

"Well really, anything goes,” Dello said. “We've had warm ENSO neutral years. We've had cool ones. Wet ones, dry ones."

Dello said a persistent blob of unusually warm water closer by in the North Pacific contributes to the Climate Prediction Center's forecast of "above normal" temperatures from October to December across the Northwest.

"The skiers were super-excited when the La Niña Watch was first posted because it tends to mean big, cold winters with big snowfalls here," Dello said in an interview. "They might be a little bit bummed at this outlook, but like I said, anything goes.”

“We could get a big snowfall in a 'neutral' year,” she added. “That warmer than normal temperature outlook though is a little concerning."

The National Weather Service's three-month outlook also contains a higher probability of above-average precipitation across northern Washington and northern Idaho.

University of Washington Professor of Atmospheric Sciences Cliff Mass observed that neutral winters carry some risk of unusual or severe weather.

"The biggest windstorms, strongest atmospheric rivers and largest snowstorms tend to like neutral years," Mass wrote in an email. "These are infrequent events, but when they happen, major problems occur."

Mass predicted if the current outlook pans out, water supplies "should be average for next summer."

The federal Climate Prediction Center assigned a 55 to 60 percent chance for neutral conditions in the equatorial Pacific to last through fall and winter.

"The forecaster consensus prefers this outcome, which is supported by the lack of significant anomalies in several indicators over the past month (winds, convection, subsurface temperatures)," the forecast synopsis said.