National Weather Service Severe Thunderstorm Warning/Tornado Warning question?

Question

Why do they not do a whole county under a warning, but rather a box shape?

Answer 1

Because the entire county is not always in the path of the storm.

Answer 2

I have always wondered that. We are under one now actually...

Answer 3

We are trying to limit the amount of warned area in order to reduce the amount of false alarms.  This is particularly evident over the western part of the country, where counties are in some cases very large.  Thus we don't want to warn say, 1500 square miles for a storm that tracks over 50 square miles.

Answer 4

So you know exactly where to expect it.  Counties can be fairly large.