La Niña Strengthens, Good Ski Season Expected
If you looked east across Lake Washington on one of our few sunny days this past month, you’ve probably seen the gorgeous, snow-tipped peaks of the Cascades glistening in the weak November sun. The last two Novembers saw very little mountain snowfall, so it is so refreshing to see a thick blanket of white covering the mountains before Turkey Day. As of 11/20, Crystal Mountain was planning to be open by Thanksgiving, and Stevens Pass is aiming for December 2. Although Snoqualmie Pass hadn’t announced an opening date as of 11/20, there is already more than enough snow there to open up for limited operations. I am optimistic that this snow will continue to pile up for the rest of 2020 and well into 2021, and I am hopeful ski resorts will be able to stay open, operate in a safe way, and provide some much-needed outdoor recreation during these next few months.
We saw a classic La Niña pattern for much of November, with a steady parade of moderate/strong storms arriving from the WNW and giving us gusty winds, moderate/heavy rain, and gobs of mountain snow. A “weak” La Niña was already present in August in September, but it quickly strengthened to a “moderate” La Niña through October and November. As we head into December, it is looking increasingly likely that the current La Niña strengthen to a “strong” La Niña that slowly weakens in spring 2021.
During the first half of the “storm season” from October through December, La Niñas have historically given the Pacific NW above-average precipitation with near-average temperatures. But during the latter half of the storm season from January-March, La Niñas tend to be wetter & cooler than average, both allowing snow to build up over the Cascades late into the season and making it slower to melt during the spring. Particularly strong La Niñas, like the La Niña of 2007-2008 or La Niña from 2010-2011, can cause cooler and wetter-than-average weather to persist into May. I still remember skiing in the Alpental backcountry on Memorial Day 2008 with my mother, the last day there of the epic-2007-2008 ski season.
Will It Snow at My House this Winter?
La Niña years are consistently snowier-than average in the mountains, but the story in the lowlands is a bit more complex. La Niña winters tend to have more snow days than Neutral Years, but Neutral or weak El Nino years seem to have the biggest snowstorms. I can’t guarantee that we’ll see any flakes in the lowlands this year, but I think there’s a higher-than-usual chance for at least a few snowflakes to fall over Leschi this winter even if we don’t see any major snowstorms.
Charlie Phillips is a Madrona resident who received his B.S. in atmospheric sciences from the University of Washington. He works in Portland as a meteorologist. Check out his weather website at Charlie.weathertogether.net.