There's only a 7% chance of a White Christmas in Seattle (defined as 1 inch or more of snow on the ground) for any given year, but Mother Nature gave many places in the Pacific Northwest their first White Christmas since 2008 as a low pressure system made landfall on the Northern Oregon Coast, drawing down cold, dry Canadian air while still spreading precipitation northward into the area. Amounts generally ranged from 1–4 inches around the area, with less near sea level and more up on the hills. The Leschi neighborhood saw approximately two inches by the lake, while amounts were closer to three inches on top of Madrona Hill. Sea-Tac airport, where our official weather observations are taken, recorded 1.6 inches on Dec. 24 and one inch on Dec. 25, with that one inch tying the record for Christmas Day set in 1965.
A snowy view from the lookout above the stairs by East Olive Lane. Taken December 25, 2017 by Sara Robertson
Snow is exceedingly difficult to forecast in Western Washington due to the fact that temperatures are often right on the edge for accumulating snow. This system was initially predicted to make landfall near Astoria, but it instead made landfall near Garibaldi, decreasing the northward extension of above-freezing air in the mid-levels of the atmosphere and keeping precipitation as snow all the way to sea level. Even Portland saw snow on Christmas Eve, though they switched to freezing rain shortly before midnight as warmer, Pacific air spread into the region aloft while cool, easterly winds kept temperatures below freezing in the metro area.
With an average of 4.3 inches per month, January is the snowiest month of the year for Seattle. Even though the days are getting longer, the northern latitudes are even colder in January than December due to the “thermal inertia” of the atmosphere—i.e. the lag in response between incoming solar radiation and the temperature of the atmosphere. January 1950 stands out as a particularly brutal month, with an average temperature of 24.85 degrees and 12 single-digit low temperature readings at Sea-Tac airport from January 1st to February 3rd. January 13th, 1950 featured one of the worst blizzards in Seattle history, with temperatures remaining in the teens all day and 20 inches of snow at Sea-Tac airport.
While it’s a safe bet to assume January 2018 won’t be as snowy as January 1950, it’s still too early to know if we’ll witness any other brushes with snow this month. But seeing as five of the past 10 January's have seen measurable snow at Sea-Tac airport and three of the remaining five have seen a trace, I’d say the odds are in our favor to have at least one more brush with the white stuff in the Seattle area this month.
I hope you had a fantastic Christmas, and here’s to a splendid 2018!
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.