Prevailing Visibility

Prevailing visibility is the greatest horizontal visibility, equalled or exceeded throughout at least half the horizon circle, observed from a meteorological station. It is the visibility figure reported in METARs and used for determining VFR weather minima.

Prevailing vs. Flight Visibility

Prevailing visibility is a surface measurement. Flight visibility is what the pilot sees from the cockpit. They can differ significantly. As PIC, you are responsible for complying with flight visibility requirements — not simply the reported prevailing visibility.

Sector Visibility

When visibility differs significantly in different directions, a sector visibility may be reported in addition to prevailing visibility. For example, “Vis 1 SM, Vis W 1/4 SM.” This warns pilots that certain approach directions may have much lower visibility than the prevailing figure suggests.

Related Terms

See also: Flight Visibility, Ground Visibility, Visibility.