Many of these gyrations were associated with amplified upper level wave patterns with ridging associated with dry conditions and a deep east Pacific trough with wet situations.
Here is the jet stream forecast (300 hPa--around 30,000 ft, lines are heights, shading is wind speed)
for Friday at 7 PM and Monday at 4 PM.
Can you see the difference? On Monday, we had a ridge of high pressure and weak winds aloft over us, while on Friday a strong jet stream--oriented almost east-west--comes right into the southern Oregon coast. Think of the jet stream as the conduit of storms and rain. The hose is directed at us.
Let me show you the forecast 24-h totals of precipitation for the next 3 days. Lots of rain as a progression of systems comes in. And it doesn't end there.
With the jet stream core south of us, the air will be cool enough to snow at least down to 4000 ft.
Here is the 72 h snowfall map. Several feet in the north WA Cascades and its extension up to Whistler. Whistler will be able to offer decent skiing I suspect. Snoqualmie will not be able to open.
My KPLU Radio Segment
I just wanted to remind everyone that I do a weekly weather segment on KPLU radio (88.5 for many of you) at 9 AM every Friday (like tomorrow). It is also available on their web site (http://www.kplu.org/). I generally give the weekend weather forecast and talk at depth on some topic.