La Niña Odds Favor Cooler, Wetter Winter For Western Washington

SEATTLE — With another sunny weekend ahead — and still no rain in sight — there is no better time than now to daydream about the chilly specter of winter.

Federal climatologists see favorable odds for La Niña conditions developing in the fall and lasting through the winter season, which typically means cooler and wetter weather for the Pacific Northwest. In La Niña years, temperatures in the Pacific along the equator are cooler than average, with weather impacts varying by region.

"La Niña affects US weather through its impact on the Asia-North Pacific jet stream, which is retracted to the west during a La Niña winter and often shifted northward of its average position," writes Emily Becker, a NOAA research scientist. "Generally, La Niña winters in the southern tier of the US tend to be warmer and drier, while the northern tier and Canada tend to be colder."

For Washington, a strong La Niña winter tends to mean more rainfall and more snow. Last winter is one such example, where the mountain snowpack landed well above average, and a February storm brought Seattle its snowiest day in decades.

According to climatologists, having two La Niña winters in a row is far from uncommon.

"In fact, of the twelve first-year La Niña events, eight (!) were followed by La Niña the next winter, two by neutral, and two by El Niño," writes Tom Di Liberto, a consulting climatologist for NOAA. "Honestly, with those numbers, it would have been more surprising if we thought neutral conditions would continue all year."

While far from a sure thing this many months out, and conditions neutral now, meteorologists with the Climate Prediction Center said consensus is building among long-range computer models for La Niña emerging in the September to November period and sticking around through winter.

NOAA updates its La Niña or El Niño forecasts every month, and readers can find more details on the latest outlook online.