What unit is primarily used when forecasting visibility in a TAF?

In Terminal Aerodrome Forecasts (TAF), visibility is primarily expressed in statute miles or meters. Statute miles are commonly used in the United States, while meters are often favored in many international contexts. This dual usage reflects a standard practice in aviation that allows for consistent understanding and communication of visibility conditions which are crucial for flight operations.

Using statute miles or meters helps pilots and air traffic controllers quickly assess visibility, which is essential for making informed decisions regarding takeoffs, landings, and overall flight safety. Other potential measurements, such as nautical miles or feet, are not standard for visibility forecasting in TAF, as nautical miles are largely reserved for distance over water or for navigational charts, while feet are typically used for altitude rather than horizontal visibility.