Jim, yes, what you are doing is layering! You even said so!

That's three layers right there. Just like me, you're adjusting your insulation to your activity level and the temperature. The big difference is that it's lot colder in the winter on your side of the Cascades! I actually was thinking more of 3-season high mountain hiking, especially in the Rockies (I was thinking the Wind Rivers and I'm pretty sure W_D was, too!). The difference is that I will strip or add layers as I go, mostly to avoid sweating if at all possible. Also, over here, we have to be prepared for rain, even at higher altitudes in mid-winter. That means the rain gear has to go over the down or synthetic puffy jacket unless, like yours, they have waterproof shells. Personally, I wouldn't want to carry the extra weight of the equivalent of two sets of hard shells, but that's one of those YMMV things.

An amazing number of folks will go out with just one heavy jacket and try to hike/ski/snowshoe in it, getting all sweaty (thus getting their insulation wet) and then chilling as soon as they stop whatever activity they are doing.