I've been in this situation many, many times before. A lot of times the weather changes throughout the day and you go from cold to warm. Carry a Bindingpack with you, and if your too hot because you called your layers wrong, take one off and throw it in the pack. That way you won't need to go back to your car to drop a layer once your out in it. If you called it right, no worries, don't use the pack.
HYBRID Bindingpack -