This idea was inspired by WUnderground’s Road Trip weather, but I envision something much more configurable, useful. Basically, to be able to set dates (and optionally, times) for a list of locations and see the current weather forecast for each time/date combination. Obviously, it would update with new forecasts as time passes.
It could be standalone (enter your itinerary manually), but would be better if it integrated with something like TripIt. It’d also be nice if you could enter endpoints for driving directions (for a multi-day road trip) and build from that.