Multiple waves of low pressure will move ashore over the next several days across the Pacific Northwest. An arctic front will move through western Washington late tonight into Tuesday morning, dropping freezing levels to around 500 feet Tuesday afternoon and eventually to the valley floors Tuesday night.
The Washington and Oregon Cascades will get absolutely pounded with snow throughout much of this week. In general, the Cascades will receive a wide spread 6-10 FEET of snow by Friday, but some of the highest peaks could receive more than 16 FEET! With the pattern the Pacific Northwest will be locked into the remainder of the month, it is not out of the question that Mt. Rainier in Washington sets the new record for the most snowfall in a month. The current record of 304 inches, or 25′ 4″, is held by Mt. Baker in Washington.
While the Cascades will definitely receive feet upon feet of snow, what about the lowlands, including Seattle and Portland? As the freezing levels drop to the valley floors Tuesday night into early Wednesday, both Seattle and Portland will likely see accumulating snow. Prior to Tuesday night, both cities will see some light snow showers, accumulating an inch or two. The storm really gets going Tuesday night into early Wednesday before the snow changes back to rain. Below is a graphic from the University of Washington depicting 24-hour snowfall accumulations for western Washington ending Wednesday afternoon.
University of Washington WRF 4-km forecast of 24-hour snowfall accumulations.
As you can see, the UW 4-km WRF brings significant snow across just about all of western Washington. During this period Seattle is forecast to receive around 6 inches or so. Just north of Seattle is expected to get quite a bit more snow than downtown. Do you know why this is? This is due to the Puget Sound Convergence Zone. My friend Luke Madaus wrote a great blog about this a while back.
While I do think Portland will see some accumulating snow, they will not see near as much as Seattle. Portland will be straddling the rain/snow line for a while Tuesday night, but I still expect downtown to pick up an event-total of 2-4 inches. Below is a list of a few cities in the Pacific Northwest along with my snowfall forecast for that city ending Wednesday afternoon.
- Olympia, WA: 16-24 Inches
- Everett, WA: 8-14 Inches
- Seattle, WA: 5-10 Inches
- Longview, WA: 4-8 Inches
- Gresham, OR: 4-8 Inches
- Portland, OR: 2-4 Inches
**Worth noting: Average annual snowfall, as measured at Sea-Tac Airport, is 8.1 inches.**
