In counterpoint to Wildman's excellent post, I CAN relate an emergency situation that would provide advance notice and public announcement of impending evacuation. I live in an area that can flood. It has already happened twice.

Accordingly my suggestion is to also consider setting up additional contingency supplies at locations determined by you to be your evac. destinations ie: parents, grandparents, in-law's, siblings, trusted friends, etc. This can reduce your load provided the situation allows you to get to your contingency supplies.

If you can determine the location you would most likely be able to head to, stock that location with supplies. It may not be possible for you to carry everything you need, let alone pack, on a moments notice.

You may even be at work when an emergency strikes. Maybe you won't even be able to go home in the first place...This has happened to me.

In other words, reduce what you're carrying and place it, in advance, where you would most likely attempt to head. The caveat of course is to consider this stock as backup. But backup's have funny ways of turning into our primaries don't they?

Every situation is unique but the concept is basically like setting up "safe-houses".

For example: My area is in a flood zone. My in-laws are a driveable distance away on high ground. I've got supplies there that would allow me to show up basically with nothing in my pockets (god forbid!), be comfortable, self-sufficient for a couple of days, and be a minimal load on my in-laws. Obviously this presumes I'll be able to drive there. But your "safe-house" may be walking distance. In addition to the basics, consider some toys, children's books and kid friendly snacks, maybe even a pack of diapers.

We can't control the type of emergency or the timing but we can prepare locations that we would likely decamp to in an emergency. Consider it in addition to the useful advise already posted.