MIKE MOSS SAYS: Denise, The specifics vary depending on the type of weather involved, but generally a watch indicates that atmospheric conditions are becoming favorable for some type of high impact or potentially dangerous weather event, but it has not begun or remains far enough in the future that confidence is fairly low that it will occur in a given location.
A warning is isued when an event is underway or confidence becomes reasonably high that it will occur.
For example, a tornado watch is issued when conditions across a broad region are favorable for tornado formation, but if a tornado is sighted or is indicated on radar, a warning will be issued for the specific county, or portion of a county, that will be in the path of the storm. Likewise for severe thunderstorms.
On the other hand, for winter storms and hurricanes, a watch will be issued when it appears there may be one of those systems affecting the watch area within the next day or two, while a warning would be issued when the event is less than 24 hours from starting and confidence becomes fairly high that it will develop as forecast.
You can see some of the criteria used for local watches and warnings by the Raleigh National Weather Service Office at