Visibility

Visibility is the greatest distance at which a prominent object can be seen and recognized by an observer or by a specified instrument. Aviation weather reports express visibility using the convention and units applicable to the report, such as statute miles in many US reports or meters in other systems.

How it works

A METAR can report prevailing visibility, directional visibility, runway visual range, or restrictions caused by weather phenomena. A group such as 10SM means visibility of 10 statute miles in the US format. A lower value can be associated with fog, mist, precipitation, smoke, dust, or another obscuring condition.

Visibility is not the same as ceiling. Ceiling describes the lowest broken or overcast layer, while visibility describes the horizontal or slant distance at which objects can be seen. Both can change quickly and can differ between an airport sensor, runway, and route.

Example

A report containing 3SM BR indicates visibility of 3 statute miles with mist. A separate cloud group may show a ceiling, or there may be no ceiling reported. A pilot uses both values when comparing the observation with the applicable operating rules.

Why it matters

Visibility affects traffic see-and-avoid, runway environment acquisition, navigation, and regulatory weather categories. It is time and location specific. A report at one airport does not establish visibility along an entire route or at the destination later in the flight.

Review the observation time and compare the METAR with the TAF. Current aviation weather products are available from the NOAA Aviation Weather Center.

Related terms and tools

• Ceiling
• Dew point
• METAR