This pattern tends to be self-reinforcing and can be stable for days. The current model forecasts shows this pattern setting up on Friday and lasting for quite a while. Let's take a look at the upper level (500 hPa, about 18000 ft) for several times, starting with the forecast for 10 PM on Friday. The upper ridge has begun to push northward over the eastern Pacific.
and even late Tuesday, it is holding on!
You get the picture...an example of an amazing persistent blocking pattern. No precipitation over the West Coast, and yes the threat of persistent low clouds and fog over interior valleys (including Puget Sound and the Willamette valley)
Based on this pattern, the National Weather Service's Climate Prediction Center is going for below normal precipitation over both the 6-10 day (left image), and 8-14 day (right image) periods. We get stuck in a dry situation, the eastern U.S. in a wet one.
It is good we have a decent snow pack right now....there will be little additional accumulation starting Friday.
We are now running out of the time for real winter weather. Generally, it is rare to get major windstorms, precipitation events (atmospheric rivers), snow, or anything else after the third week of February around here. We know nothing is in store for the first two weeks of the month. Not much time after that.
Finally, the meteorological honor of Seattle citizens is at stake. Atlantic Monthly has called us "weather wussies" because we are sensitive to a little snow. Let them check out our hills or the ice that tends to develop after light snow. Consider that East Coast types, such as the Atlantic editorial staff, give names like "Storm of the Century" and "Perfect Storm" to events that would invoke a tepid shrug from a Northwesterner. We know who the real weather wimps are.