Latest models are in. Some of you will see snow. But no big snowstorm that will last for days.
The first with snow will be the northern Willamette Valley and Portland environs, which should catch some light snow from precipitation moving up from the south. It won't get north of Centralia.
Then on Sunday an upper trough will move through bringing a surge of cooler air from the north and snow showers..mainly over the northern side of the state. There will be considerable rain (snow) shadowing over the lowlands south of Seattle, but Puget Sound convergence snow and other snowbands will be found over the northern half of western WA. Seattle should be prepared and SDOT should be particularly staged north of the ship canal. Wherever the convergence zone band sets up could get several inches.
Then there is a break early Monday, but then a warm front will approach during the afternoon. The cool air will hold in a while, particularly over NW WA, and there will be some initial snow--perhaps several inches in some locations---before it all turns to rain on Tuesday. Warmer air will move in on Tuesday and life will be back to normal. LOTS of snow in the mountains and eastern Washington on Tuesday.
This is a very difficult forecast with the snow hardly being uniform over the region. There is uncertainty...but the above is my best shot. We are not talking about a major snowstorm!
PS: I will be giving a public lecture--"The Secrets of Snow"--at Third Place Books in Lake Forest Park on December 17th at 7 PM, followed by a book signing. In this talk I will describe the unusual circumstances that have to come together for us to get a big snowstorm, details of convergence zone snows, the Fraser River Gap flow, arctic fronts, and more. My favorite topic.