Muley Buck
WKR
For those conditions you need a true cold weather down parka and pants with a waterproof jacket and pants over them.
This is what has proven to work for me and those I work with-
Wicking base layer top
Light to mid weight fleece top with a hood
Some kind of active insulation top (Polartec Alpha) while moving if it’s single digits
Expedition weight down coat with a good and 10 plus ounces of high quality down (or equivalent synthetic)
Rain coat big enough to fit over everything else
Wicking base layer pants
Whatever normal pants you like (Sitka Timberlines)
Medium weight base layer (preferably with zippers or buttons)
Expedition weight down pants with 10 plus ounces of high quality down (or equivalent synthetic)
Rain pants big enough to fit over everything else
Good toboggan or hat
Glove liners or light leather gloves
Mittins with flip off fingers
Extra pair of socks
Hand heaters
Puff jacket and pants in the pack, wear only what is absolutely necessary to avoid sweating. When you get to the glassing spot, immediately put on all of your layers with the rain suit over everything. Do it immediately- do not wait to cool down. You want to trap the heat that your body is producing, and use it to cook your clothes dry of sweat. Change socks to dry ones (place wet socks inside coat). Then pop the Jetboil out, heat water and get something hot to drink- bullion cubes, coffee, tea, whatever. Eat something. In really cold weather we average no more than 30-45 minutes between eating, or drinking something hot.
The above above works for most people until around 0 degrees. After that, eaithwr a true arctic weight down suit or sleeping bag is added.
Some need more, a few will need less.
I do this almost exactly the same. Only difference is I run the First Lite Tundra balaclava for head gear. This system is the most efficient and effective I've ever used.