I think that's a good approach also. When I lived in Northern VA we saw the mad rush to the stores when ever a storm was coming in or there was a threat of snow. Nothing like CO of course but big for that area. I lived with my sister and we got into keeping a pantry of food items. She cooks a lot and so we had powered milkOne storm we couldn't get out of the house for 5 days but we had food.
If you point out the obvious storm/loss of electricity/flood scenario most people could relate.
For the communications, I don't know if big brother can or would shut down cell towers but the problem, IMHO, is overload. If everyone's trying to make a call it will overload the systems (towers, phone lines, data centers)
Back when I used to work for a certain telco, they managed PIN's for emergency responders. People with the pin would have their call placed at the top of the line when dialing a number. While it's important for you to be able to talk to your family the responders are using the call for status reports, coordinate efforts and such (you hope).
I know the GPS satellites are controlled by the military and civilian access can be turned off which is why there was a stink years ago when the Europeans were doing their own version of GPS. US Government can't shut that one down. Maps and a compass baby!
Ham radio's should be fine since they operate on radio waves unless there's a jammer on the frequency. You and the receiver would need power to the equipment but the actually capability would be there.