The last two weeks of November are climatologically the wettest period of the entire year.
This year won't disappoint.
Let me begin by showing you a neat chart never before seen on this blog. The TOTAL precipitation forecast for the next 8 days from the National Weather Service GFS model. This model has relatively modest resolution, so it is not capturing the full amounts over our terrain, but you will get the picture.
Very wet from coastal BC down to northern CA (5-10 inches is commonplace, with northwest CA "enjoying" 10-15 inches. No rain in Arizona and New Mexico and much of the NE U.S.
Lets take a look what the higher resolution UW WRF model is giving. Let me first show you the first 72 hr (ending 4 PM on Saturday). Modest precipitation over western Washington, but the heaviest rain (2-5 inches) over the mountains of NW CA.
Why so much rain? A large, cold trough will form over the eastern Pacific, establishing a persistent flow of moist air from the west and southwest (see upper level map for next Monday at 1 PM):
What about snow in the mountains?
Temperatures will be marginal in the lower passes (Snoqualmie/Stevens), so there should be a mixture of rain and snow there---I doubt they will have enough to open for Thanksgiving. But higher ski areas (Crystal, Baker) should get substantial amounts (foot plus) and may be able to open by Turkey Day. Keep tuned.