On a recent trip, I tried to go pretty light and struggled with whether or not to bring hard shell tops and bottoms. I have a Patagonia Rain Shadow jacket and some full zip North Face pants (total weight about 1.5 lbs). It was two-day trip and the forecast called for good weather, no wind, not too cold, and no snowcover anywhere on the route (Southern Sierra). As always, the hard shells stayed in the pack from car to tent to summit and back. I knew they would, but I just couldn't bring myself to leave them behind.
I'm curious how others make this decision. For a weekend trip*, do you pack your hard shells only when the forecast calls for foul weather? Do you always bring them just in-case? Do you only bring the jacket and leave the pants behind?
*For an extended trip the decision seems pretty obvious to bring them, and for a day trip the forecast should suffice.