Tornado watch means conditions favor tornadoes and officials expect they could form, NOAA's Storm Prediction Center says, and these watches often cover multiple states.
The SPC typically issues a watch four to eight hours before conditions may support tornado formation, giving people time to stay alert and prepare.
A severe thunderstorm is defined by the National Weather Service as producing hail about the size of a quarter, at least one inch in diameter, and or wind gusts of fifty eight miles per hour or higher.
When forecasters believe storms capable of reaching those thresholds could develop, the National Weather Service may issue a severe thunderstorm watch that can span large areas and last several hours.
By contrast a severe thunderstorm warning means a qualifying storm is occurring or imminent, issued by local National Weather Service offices when radar or trained spotters detect the hail or wind thresholds.
An advisory covers weather that does not meet severe criteria but still causes problems, such as gusty winds, small hail or heavy rain, and it warns of travel inconvenience or hazards.
Outlooks come earliest and signal the potential for storms days before watches or warnings, and NOAA's Storm Prediction Center categorizes outlooks on a one to five scale as marginal, slight, enhanced or high.
Safety Actions And Warning Details
A tornado warning indicates a tornado has been spotted on the ground or is indicated on radar, and local National Weather Service forecast offices issue warnings for smaller areas, often parts of a county.
Warnings typically last thirty to forty five minutes, and when one is issued people should take action immediately and move indoors to protect themselves.
The safest places during a tornado warning are in a basement or an interior room on the lowest floor away from windows, according to guidance in the reporting.
In extreme situations forecasters may append a tornado emergency to a warning, which is not a separate warning type but uses more urgent wording to indicate a life threatening and potentially catastrophic situation.
Residents in a tornado watch area should review safety plans and be prepared to move to shelter quickly if conditions worsen, while those under warnings should seek shelter right away.
