...think about what else I'll need. 
Mark
I know this may sound silly, but if you have MotoX or skiing goggles then they can be very useful. If your visor ices, etc. you can use the goggles and keep riding.
If it's snowing heavily when you're walking around the site you will be able to see where you're going. I found my MotoX goggles invaluable for this reason in 2000.
And, of course, a pee bottle. Who wants to get out of their tent at four in the morning when it's minus 15?
GC