Welcome winter: Experts cite potential for abnormal conditions in the Pacific Northwest
Washingtonians might have to stop giving umbrellas the cold shoulder, because this winter could be too cold and wet to bear.
The National Oceanic and Atmospheric Administration’s winter weather outlook predicts colder temperatures and heavier rainfall in the Pacific Northwest. The report identifies a 40-50% chance that temperatures will fall below average, which is the greatest percentage compared to the rest of the United States. Chances for above average precipitation are estimated at 33-40%.
“It doesn’t say how much below normal,” said Kirby Cook, Science and Operations Officer at the National Weather Service’s Forecast Office in Seattle. “It’s not really equating to a specific temperature, it’s just that odds are a 40-50% chance that they will be below normal.”
These abnormal conditions are due to a projected La Niña episode, which is generally characterized by colder winter conditions in the North, and warmer temperatures in the South.
According to the NOAA’s website, the El Niño-Southern Oscillation cycle is a phenomenon when abnormal climate patterns in the Pacific Ocean disrupt the ocean’s upwelling process. Normally, trade winds, which revolve the Earth around the equator, head west and draw warm water from South America to Asia. Then, cold water rises to replace it.
However, when trade winds lessen, warm water is pushed toward the West Coast, resulting in warmer and dryer conditions in the northern U.S. La Niña is the exact opposite — the increase in trade winds results in more upwelling and subsequent heavy precipitation and occasional flooding.
Episodes of El Niño or La Niña usually span 9-12 months but can sometimes linger for years. The most recent La Niña was a “triple dip,” lasting three consecutive years. Beginning in September 2020 and concluding during the early months of 2023, it was the third “triple dip” to occur in history, as well as the first of the 21st century.
The Climate Prediction Center said La Niña could emerge starting in September through November. If it occurs, this episode is predicted to last through January to March of next year.
On Nov. 11, CPC reported that ENSO-neutral conditions are currently identified, and there is a 60% chance La Niña is favored to emerge this month.
Residents in Kitsap and the Puget Sound are already feeling it. The National Weather Service Seattle office’s daily weather briefings this week detailed storms passing through — warning of strong winds, flooding on the Skokomish River and heavy snowfall over the North Cascades. Another storm could pick up over the weekend as well.
Absent from NOAA’s outlook were any predictions about snow. According to Cook, since outlooks are not reflective of specific temperature forecasts, it’s difficult to equate probabilities of winter conditions to snowfall, especially in lowland areas.
“But what you can say, is if we do have cooler than normal conditions and wetter than normal conditions expected over the season, odds are that will affect snowpack in the mountains,” Cook said. “That means the snow level will probably be a little bit lower. So more of that precipitation would be expected to fall as snow in the mountains because of this lower snow level. Especially during La Niña seasons, the expectation would be that we have a little more snow packed in the mountains.”
The outlook frames the general characteristics of the winter, therefore, there is still a wide variety of weather events that can still occur, such as floods, winds and even sun. Due to these potential variabilities, Cook recommends regularly checking the forecast in order to inform planning and travels.
“That’s the bottom line with weather in the [Pacific] Northwest, is it can vary quite a bit,” Cook said.
On the second Thursday of each month, CPC publishes a report measuring indicators of the ENSO cycle, so for the most current updates about the La Niña watch, visit their website to view the report or the NWS’s website for forecasts ranging from the national to local level.
