A comet hitting the Earth scenario, causing an ice age. The ice age could last for hundreds of years. Yes it would be good to know whats going to happen, but you can't. That is the nature of a catastrophe. The prep you must do is food stores and weapons caches and skill learned to survive. The above is not all that you will need, see CSC's list and others post who have listed basic needs. What you are trying to do is buy yourself time to learn new skills in a new environment or status. Then you will be able to move yourself to a better area or learn how to make it in the new world that exist now.