Originally Posted by 575rider
bring a gallon of water, throw a sleeping bag in the back, good flashlight, a wa to light a fire, and a bag of trail mix
Revert back to your Boy Scout days and "Be Prepared".
given your location, guessing you haven't had to pack a true winter survival kit...
A gallon of water just becomes a solid block of ice that will do nothing for you. If you are in a multi-day survival situation in the winter, you will have tons of relatively clean frozen water all around you already.
If you stay with the car (which you generally should), warmth and fat calories are #1 and #2, pretty much everything else is optional if you have those met. Lack of either of those in a winter survival situation in a car will kill you. Snow is your water, and shivering will keep you warm, if you have some decent clothes. (hence the fat calories, shivering burns LOTS of calories!)