First of all, anyone traveling in the snow belt in the winter should have some basics in their car:
- Blankets
- Warm clothing
- No less than 1/2 a tank of fuel at any time and always fill up if you know a storm if coming. I will top up my tank before a storm hits even if I've only driven 30 miles or so.
- Cell phone charger
- Emergency food and either water or a water bottle to melt snow
Things I have added beyond this:
- CB Radio
- Ham radio (x2)
- Road flares
- Emergency flare launcher (available at any boating store)
- Fire starter
- Tarp
- Recovery gear
If you are stuck without cell coverage
stay in your car. A car is much easier to find than a person, it offers shelter and heat. Your engine will run a very long time at idle on half a tank of fuel, just be sure to crack a window a little to get some fresh air and make sure you aren't getting any exhaust into the cabin.
Keep trying with any communication gear you have, your phone might not have service right now, but keep trying. Get out of the car as often as you need to keep it clear. Turn on all your lights, brush the car off, set road flares, whatever you need to do so you don't look like a snowbank - when plows do come through you don't want to get hit by one.
I usually prepare my recovery gear. I get my tow strap hooked up and ready to go, maybe tuck it into the trunk so it doesn't get buried in snow and ice. This way if someone who isn't a tow truck comes along I can get rescued using my own gear. If you have traction mats or other specialized gear, you might as well include it in your vehicle if you know you will be out in the storm.
Most importantly, tell someone where you are, where you are going, the route you are taking, and your ETA. Have them call Highway Patrol if you miss your scheduled check-in and can't be reached.