Always carry a sleeping bag (or two) and a supply of chocolate bars during the winter ... never know when they'll come in handy
(Clumping kitty litter is handy too, for getting traction when you need it)
Every winter my truck got a 35L backpack stuffed full of MountainHouse (among other things) Enough food to walk out if I needed to.
Didn't have to worry about much else, because winter gear, sleeping gear, tarps, tools, and etc were onboard all the time (It's a mountain truck after all). Added some spares, and counted on natural accumulation to build that inventory.
Tech tip: When you buy a new set of Carhartts, have your old ones professionally cleaned and vacuum sealed = The whole mess of em will fit under your seat. That's where mine lived, all the time. Same with my old mukluks - They just lived behind the seat in the truck. That way I always had em, and they worked as dry spares if I was in my new set.
But you should always, always, always have hard weather gear onboard. Even if you ain't planning on leaving town. If you've ever needed to walk out, you'd understand.
