The problem is, this is a somewhat committing trip. Once you are at Trail Camp, you will have do deal with what the weather gives you, and you usually will not really know in advance.
I've usually found wind to be the main problem, biting, arctic-cold wind, and having a tent to hide in was wonderful.
I sort of think that you need to, at minimum, have something that will allow you to survive, should it start to pour. Nothing won't do it. One of those disposible bivy's will(Adventure Medical Thermo-Lite Bivy). Frankly, I'd think a bivy to be a minimum, but I'll bet you could get by with a tube-tent.
Think of it this way....if there is an afternoon thundershower, if you have no shelter, your trip is over, even if the next day is glorious.