When severe weather conditions become apparent, the U.S. Weather Bureau describes conditions by two (2) classifications, a Watch or a Warning. This applies to the reporting of severe thunderstorms, the approach of weather conditions favoring the formation of tornadoes, a winter storm condition, etc.
- A Watch becomes effective when atmospheric conditions are right to produce the particular weather phenomenon.
- A Warning means that the weather condition has been spotted and prompt action must be taken for safety.