The most important feature of your outer layer is its ability to keep the elements out. It should be waterproof and windproof. Beyond that, you have a decision to make on whether you opt for a shell or an insulated option.
- Shell jackets and pants are highly durable yet lightweight with little-to-no extra insulation. They protect you from the wet and wind but won't add much warmth. Though, their streamlined versatility is an asset in variable conditions.
- Insulated jackets and pants keep elements out and warmth in with (often synthetic down) insulation. Although an insulated outer layer will keep you warmer, it will add bulk and give you more limited layering options.
If you tend to "run hot," shells might be a better choice while insulated could be the way to go if you "run cold." Either way, many snow jackets and pants feature zippered vents to release excess heat without shedding a layer.