Difference between WARNING & WATCH
A WATCH means that the potential exists for the development of severe thunderstorms or tornadoes, depending upon the specific type of watch issued. In the case of a tornado watch, this DOES NOT mean that a tornado has been seen or even indicated on radar...it just means that conditions are favorable for the formation of tornadoes in thunderstorms. Similarly, a severe thunderstorm watch means that conditions are just conducive for the development of severe weather, and DOES NOT indicate that severe weather has been reported. While no immediate action on the part of the general public is required for the issuance of a watch, citizens should keep up to date on the current weather situation and be prepared to seek shelter if necessary.
A WARNING, on the other hand, requires more immediate action and should be taken seriously. A severe thunderstorm warning indicates that severe weather is imminent in your area or is already occurring (based on either human observation or doppler radar). The term severe refers to hail greater than or equal to 1.00" in diameter and/or wind gusts that meet or exceed 58 mph. Although these storms can also be associated with dangerous cloud to ground lightning or heavy rainfall that is capable of causing flash flooding, neither of these two items serve as criteria for a severe thunderstorm warning being issued.