Ok, so its winter. We all saw that coming with the end of fall right?
It happens every year. What also happens every year, at least in the province of Canada that I live in, we get some snow.Not always a lot but if you travel out of the larger cities it usually means a mountain pass or two until you find the next cities and towns. So what does a prudent person do? They prepare. This doesn't make them kookie 'Preppers' with 500 pounds of rice and flour in the basement, it shows forethought. I am a Scouts Canada leader (officially we are called Scouters now) and we teach the kids the old adage: Be Prepared. Let's move on to the planning part.
What do you need to do? First off, get that seasonal oil change and routine check up on the vehicle, easy. Don't forget to check the tires or, better yet, change over to those super fly steel factory rims with actual snow tires instead of hardly capable 'all' seasons and FILL your fuel tank..
Now, the nitty gritty, what to stash in the vehicle?
I said this was the basic version so I will keep it at that.
A blanket, or I should say enough blankets to cover your predicted passenger loadouts, travel with a partner and 3 kids? Have 2 to 5 blankets depending on size and weight. The blankets, not the other occupants.
Food and water. While food isn't essential to survive a 12 hour delay it sure makes life easier if there is something available to munch on. Consider quality food bars and 2 - 500 ml bottles of water and store them in a place that doesnt freeze up or get warm when the heater finally starts cranking it out. Leave the MRE;s at home unless you have lots of space to store them and somewhere to prepare them, you dont want to be standing outside in a blizzard trying to boil water to heat your food up. An MRE heater will work but it also produces steam, makes a hissy noise and could make a mess if it spills or at worse burns someone. 
The last essntial to think of. Waste disposal. Not only food wrappers but what if nature calls? I think we would all find a discrete way to take of a quick pee in an empty sports drink bottle but you should consider having something for more solid waste. MEC and REI carry such products in North America for under $5. At least have a pack of sanitary wipes and a roll of toilet paper with you.
Thats it, the basics. Catch up to me later for a more in depth discussion.
Find me on Youtube by searching for Paul Buikema, sorry, it won't let me put a link in.