Your options are pretty simple. You can get the Jansport Velocity Dynamic Jacket and adapt to anything mother nature throws at you, or you can develop psychic powers that let you accurately predict what the weather will do every second. The Velocity pairs a Viper nylon shell that protects you from ugly weather with a 200 weight Cisqo fleece that zips into the shell for extra warmth. Use either alone, or both together for a versatile 3 in 1 system that'll take on anything winter has to throw at you.
Bottom Line: Versatility is life in unpredictable weather.