I was in Denver during 1997 and we had 3' of snow fall overnight. Shut down the freeways and most roads. I thought I would run down to Safeway and see what was available. The parking lot was full of 4X4's and the shelves were empty. All of that in just a few hours. Don't kid yourself that if something bad happens, that people do not hoard. They understand that if things get worse, you are on your own. Back then, if the power was out, you were on your own for at least a week. People died in their cars because they were stuck in feet of snow just a few miles from town.
That storm taught me to never be unprepared again, and I think this is a great thread that reminds us about getting home and what to have in case the roads are not available. For me, the worst case would be eathquake, bridges out, raining cats and dogs and 100 miles to go.