Winter Finally Arrives to the Pacific Northwest
I like to think of Valentine’s Day as the unofficial end of winter for the Puget Sound lowlands. After Valentine’s Day, it becomes much harder to get strong windstorms, flooding rains, and most of all, widespread arctic outbreaks/lowland snow events. The northern latitudes have warmed significantly by this time, and even if a surge of particularly cold air makes it into Western Washington, the high sun angles and longer days warm temperatures on and near the surface above freezing, making it very difficult for falling snow to stick.
In many ways, it didn’t really feel like this winter began until after Valentine’s Day, especially considering how cold and snowy last winter was. We had a massive ridge overhead for the first part of December, giving a little fog to the lowlands but exceptionally warm temperatures to alpine sites with freezing levels near 12,000 feet. Another ridge moved over the area for mid January, this time bringing sunny skies and record-warm temperatures to the lowlands. Seattle hit a high of 64 degrees on MLK Day! The exceptionally warm weather continued into the first week February, particularly for regions east of the Cascades; Yakima hitting a jaw-dropping 69 degrees on February 8th. Our truly magical White Christmas notwithstanding, I’m sure many folks were left wondering if winter would ever truly take hold over the area.
The 2017–2018 winter was (and continues to be) a La Niña winter, but we didn’t actually enter and stay in a typical La Niña pattern until the second week of February. The “classic” setup for a La Niña is to have a large ridge in the Central Pacific and a large trough over the West Coast, giving us cooler-than-average temperatures, above-average precipitation, and above-average snowfall, particularly in the mountains. Until the second week of February, I’m sure many skiers and snowboarders were chagrined by the lack of mountain snowfall, but thankfully, we’ve made huge progress over the past few weeks, and it looks like our cooler and slightly wetter-than-normal weather will continue into March.
I was in Portland on February 20th, when a quick-moving, intense band of snow brought 2–4 inches of snow to the region in just a couple hours. Roads quickly became extremely treacherous, and the snow on the branches made for a beautiful sight. It’s not often when you have blooming daffodils and a giant snowman in your yard at the same time!
Interestingly enough, the Puget Sound area can see bursts of snow into early April if temperatures are cool enough as heavy showers can temporarily lower snow levels down to the surface. Intense Puget Sound Convergence Zones are notorious for dropping a quick, unexpected inch of snow on grassy surfaces. However, this snow tends to melt as quickly as it accumulated after the shower passes, even at night, as ground temperatures are well-above freezing that late in the season.
Winter may have taken its time getting started, but better late than never! Hopefully the Cascades can keep piling up more and more snow—March and even April can be extremely snowy up there.
Charlie Phillips, a Madrona resident, received his B.S. in atmospheric sciences from the University of Washington and works in Portland as a meteorologist forecasting wind energy along the Columbia River Gorge. Check out his weather website at weathertogether.us.