We recommend snowboarding boots, or waterproof moto boots, with wool socks. Try to find some waterproof socks if you are going to wear standard moto boots. If you already have snowmobile specific boots like Klim GTX Adrenalines, you’ll be just fine. Klim released the Havoc GTX snowbike specific boot in 2018, and it will be the de facto standard for backcountry riders going forward.
Goretex outerwear is the best as it will keep you the most comfortable on those classic PNW storm days. Two pairs of goggles is standard protocol as you can switch them out for a dry pair. Bring at least two pairs of warm winter gloves to switch between as the day goes on, moto gloves won’t cut it.
In our bags we typically carry a mid-weight puffy jacket to layer up under our outer shell in case the temps are cold for the tour.