The thing that caught me off guard a bit was the amount of mixing despite the lack of any real thermal gradient. The models down here handled it pretty well and showed a fairly muted downslope, helped probably by the fact we had tons of mid level moisture when the gradients were oriented properly. Looking at the 12/03 mountain wave here, it was defined by what was a TON of dry abiabatic assistance. The difference maker there was the departing inland clipper as a strong, but definitely not exceptional, low tracked well offshore. Think it bottomed out around 975mb or so. End result was pretty widespread 60-70mph gusts here in Clark County.

2020-21 on steroids.

I've been thinking about this a lot. It makes sense an event like Tuesday's which was driven largely by record low pressure off the Coast with relatively average pressure East of the Cascades would behave very differently than our usual Gap wind events driven mostly by high pressure East of the Cascades with causing a tight low level gradient localized just across the Cascades. In our usual events, the high pressure is being "pushed" through the gaps in the mountains while the pressure difference is largely capped by the usual temperature inversions East of the Cascades (and to a lesser extent West of them as well.) This causes the strongest winds to follow the bottom of the river valleys through the gaps in the Cascades and hammer areas like Monroe, North Bend, and the East Portland Metro, but quickly dissipate when they hit the open areas of Western Washington. Conversely, Tuesday's event was driven by the extremely low pressure 300 miles off the Coast which caused a pressure difference at all levels of the atmosphere. This low "sucked" the higher pressure from East of the Cascades at all levels of the atmosphere. In this case, the flow follows the path of least resistance over the mountains rather than funneling through the gaps, leading to much less wind in North Bend and Monroe because the Mountain Wave flows right over them. Then the wind buckled back downward on the West side of the mountains and hammered areas like Issaquah, Bellevue, Enumclaw, and Kent.

1988-89 was a crappy winter with a couple days of glory. We’ve had better winters recently that featured more boring autumns than this.

I don’t think Brian is far off the truth, especially if he has lived in more northern regions of the PNW. Maybe we rely more heavily on an SSW to break up a stagnant winter pattern that is spiraling towards a total failure. Or to dislodge a truly wicked airmass upon the PNW but in December and January we don’t always need a brutal airmass to give some lowland snow and cold, which I think was his point.