I'll be in the mountains the first week of November. I wear, at least three layers, and need an outer layer that's warm and tear resistant. I tend to wear overalls and coat, as opposed to coveralls. We'll be on foot, and walking/ hiking quite a bit, I suspect. The UPS truck will deliver what I need, and I have a Cabela's 20 minutes away. What say you, mountain men?
What mountains and how seasoned are you with cold?
How much coin do you want to spend?
On the fly even around zero a working body does not require much insulation to stay warm. You want the body to do what it does, vent heat out. If the body is not allowed to vent, flash off can occur and for who has experience with it, its a very dangerous phenomenon. Stop to glass, add a warm puff jacket and or pants to capture the heat the body produced burning calories as you were on the fly.
I prefer soft shell top and bottom on the fly in all temps and weather. Something wool based like Ibex will be a little more stealthy but I never had concern for quite clothing hunting. I wore cheap coated rain shells over wool and synthetic layers for years and not once did I scare away or not tip over due to my nylon. The best, I hate that term but it is what it is, layer I had used was a one piece (coveralls) soft shell from Patagonia. I wore it stand alone over Patagonia t and briefs at -40 and +50 with great success.
Several companies make high waist lowers (overalls) and it is the preferred my many mountain men because no gap-o-asis. Many of them will be labeled or in the ski clothing section.
Some tips for winter mountain travel:
If you drink coffee or caffeine, stop drinking it all at least two weeks before leaving which means start about 3-4 weeks out slowly to guard against headaches. It takes about 14 days for your body to rid itself of caffeine. Now in the mountains, a single cup will work magic to experience its full effect on the body.
Get hydrated weeks before leaving, not days. Stay as hydrated as possible in the hills.
Take baby aspirin or garlic pills weeks before leaving to aid circulation.
If you are a flatlander, ride a bicycle for training on high resistance and low seat height, this will duplicate the short power leg strokes needed for mountain work.
Mountain life or travel is more about your attitude than anything.
Hope this helps some, if you need more just ask.