Rain shell for my winter outer layer?

I think it will be fine for rain gear or a wind blocker when not moving. If you hold the fabric up to your mouth and seal it, how much air can you feel right on the other side when you blow full force? If the answer is none or just a slight amount, it should be fine.

When it's not raining but windy, you'll want a more breathable shell like a windshirt or non-membrane softshell. Somewhere around 0-15F, you'll probably find that the windshirt ices up and isn't breathable anymore. At those temperatures, a softshell will work better. I don't have much experience with it yet, but a cotton canvas anorak is my solution for a dry-cold (< 15F) wind shell.

I use a marmot super mica with a first ascent down puffy. Way warmer than any other system I've used, and I like how modular it is. I just look like a gray stay-puft marshmallow man with both on…. Granted, I don't mountaineer. If I had to worry about scrapes/rough terrain/scrambling etc etc, I'd probably have a different shell.

Depends on your definition of "winter" and the type of preceip you expect to incur, as well as your intended activity: climbing, mountaineering, snowshoeing, hiking, skiing etc.

Winter in Colorado for me equals well below freezing temperatures and so the precip is a dry snow that doesn't melt (save for a few thaw periods here and there) so liquid moisture isn't a concern. In this case I would say that a hardshell just isn't breathable enough for high aerobic activities and I would opt for a softshell hoodied jacket (Think: Patagonia Guide, First Ascent Mountain Guide etc), because not only do they block the wind like a hardshell, but they breathe much better so you won't get the sweat build-up which can make you extremely cold.

In warmer and thus wetter winter conditions then your hardshell is probably going to suffice just fine.

As mentioned, it depends on where you are. In Pacific NW winters it's raining (or mixed rain and snow, or wet snow) most of the time. Most of the time the snow on the ground is soggy, too, so I want something waterproof should I fall down (which in the days I was x-c skiing happened frequently). For such conditions you definitely want that rain jacket and rain pants.

Should it happen not to be raining at the moment, I use my wind shirt as an outer layer on top. In both cases, over a base layer plus a thin mid-layer, plus cap and gloves. When I stop, out comes the warm puffy jacket, quickly put on under the rain jacket to avoid getting it wet. I generally wear the rain pants anyway and of course carry the rain jacket because sooner or later the rain will start again!

In Colorado and Wyoming, on the other hand, any precipitation is generally powdery snow and the temperatures are colder. Generally any wind-resistant jacket and pants will also keep you dry under these circumstances. Of course it will be a lot colder, so you'll probably want more layers underneath. That's not always true; I remember quite a few bright sunny days in which, if I was out of the wind, shirtsleeves were quite comfortable even though the thermometer was well below freezing. There are actually a few times that I miss those Rocky Mountain winters!

Previously I used a Cabela's PacLite parka but now I'm going with an REI Kimtah eVent parka that I got one size larger to better accomodate my Eddie Bauer First Ascent down sweater or a 300 weight Polartec jacket.

BTW, my WPB shells are for wind and snow as well as the rare rain.

"It's breathable and all but maybe a bit too breathable and not enough of a wind blocker for 4 season backpacking. Feels a bit, I dunno, thin I guess. And maybe I need to consider something a bit thicker? Or with the right layering system will this shell suffice this winter?"

My winter system is a work in progress, yesterday I snowshoed all day breaking trail with decent elevation gain. Temps were in the low twenties, with steady snow, light winds.

Top layers were: Golite BL1 short sleeve, Ibex wool hoody, heavyweight polartec grid fleece (1/2 zip), then Marmot wind shirt. This worked well being able unzip the layers and pull hoods down accordingly. Probably should have removed one layer.

I too am trying to figure out what the right outer layers are for different conditions. I have not used my soft shell much in the backcountry, it is bulky and heavy, a 100wt fleece and rain shell combo seems lighter, warmer, and more versatile.

If your current jacket breathes well enough that you are not sweating and your layers can stay dry then use it, you have the best of both worlds.

Depends on what temps your winter is, and how hard you are working. If winter is temps less than freezing I would generally recommend shell which does not have any sort of membrane (e.g. stretch woven soft-shell, wind shirt, etc). When it's <10F and I am doing an uphill slog hiking, snowshoeing on almost any terrain, backcountry or nordic skiing I haven't found any wp/b (though I haven't tried eVENT in these conditions yet) that could keep up. Perspiration would condense on the inside of the shell and the freeze before it got pushed out… so when I took the jacket off I would find it had a frost lining. When it's frosted up it's basically an unbreathable shell.

–Mark