Plain English Meaning

A large area where mountains are blocked from view by clouds or weather, so a pilot flying visually cannot see the high ground or safely fly through the passes.

Full Definition

A widespread condition in which mountains and mountain passes are hidden by clouds, precipitation, smoke, haze, or other weather phenomena, making visual flight through or over mountainous terrain unsafe. It is one of the conditions that triggers an AIRMET Sierra advisory.

Context Anchor

Seen in inflight weather advisories and , especially in or near .