I've been set up for years in my 4x4's. In addition to the usual recovery gear, MRE's, bottled water, etc. etc. I have a couple different duffel bags that are seasonal.
In winter, I just toss in my "fowl weather bag" to add an emergency sleeping bag, two down coats, gloves including a set of battery heated gloves, wool socks, snow boots, rabbit hats, (i.e. WWI flight cap) couple of Balaclavas, ski goggles, pair of heavy Dickies insulated coveralls, wool scarves, can of Johnny Warmer fuel to go with the pair of Johnny hand warmers which are added to a packet of disposable ones, and a set of ice crampons for the boots.
Granted, that bag is 3 feet long and hard-stuffed to about 18 inches in diameter, but should I get stuck, I will NOT be like the guy in the family who tried to walk out in tennis shoes and a windbreaker. That was I think, two years ago, on an Oregon forest road. They were following a GPS, and like too many people, MINDLESSLY following it. Their little ill-equipped car got buried in the snow miles from anything. The guy didn't make it, but the wife and baby who stayed behind in the car did.
Another item I carry is a Spot Satellite Messenger. If all else fails, I can hit the 911 button and wait for rescue.
Good write up, and one that EVERYONE who heads out in winter needs to read. Frankly, I'm getting tired of reading in the news of people getting stuck who survive on eating snow and an old Snickers bar that was in the glove box. (Assuming they do survive) It's an amazing thing about modern vehicles, you can carry a LOT OF STUFF. It's not like you're making your horse tired. If you travel, summer or winter, PACK STUFF ALONG.
On edit: You can buy survival stuff on Amazon, up to and including full household kits for disasters. I carry coast guard survival candy bars, military MRE's, sealed packets as well as bottled water, emergency sleeping bag, (The winter bag just adds another) and things I can't even remember. We always joke about how we could live comfortably for days should we ever get the Jeep stuck bad. If nothing else, buy one of their pre-made 3 day survival backpacks and keep THAT in your car trunk, behind the pickup seat, or your Jeep.