Atmospheric conditions are favorable for the formation of tornadoes.
Tornado watches are issued by the Storm Prediction Center and are generally in effect for about 6 hours, usually covering hundreds of square miles. This is the time to make necessary preparations in the event that a tornado approaches your area. Severe thunderstorm watches are issued by the Storm Prediction Center and are generally in effect for about six hours, usually covering hundreds of square miles. This is the time to make necessary preparations in the event that a severe thunderstorm approaches your area. Flash flood watches are issued by the local National Weather Service Office and are generally in effect from 6 to 12 hours, sometimes longer.