A Severe Thunderstorm Watch is in effect for Calvert, Charles, St. Mary’s and several other surrounding counties in Maryland.
A Severe Thunderstorm Watch is in effect until 8pm this evening for the entire area. Scattered severe thunderstorms with damaging wind gusts and large hail are possible.
This is issued by the National Weather Service when conditions are favorable for the development of severe thunderstorms in and close to the watch area. A severe thunderstorm by definition is a thunderstorm that produces one inch hail or larger in diameter and/or winds equal or exceed 58 miles an hour. The size of the watch can vary depending on the weather situation. They are usually issued for a duration of 4 to 8 hours. They are normally issued well in advance of the actual occurrence of severe weather.
During the watch, people should review severe thunderstorm safety rules and be prepared to move a place of safety if threatening weather approaches.
A Severe Thunderstorm Watch is issued by the Storm Prediction Center in Norman, Oklahoma. Prior to the issuance of a Severe Thunderstorm Watch, SPC will usually contact the affected local National Weather Service Forecast Office (see map above) and they will discuss what their current thinking is on the weather situation.
Afterwards, SPC will issue a preliminary Severe Thunderstorm Watch and then the affected NWFO will then adjust the watch (adding or eliminating counties/parishes) and then issue it to the public by way of a Watch Redefining Statement.
During the watch, the NWFO will keep the public informed on what is happening in the watch area and also let the public know when the watch has expired or been cancelled.