Definition
A weather condition in which mountains or mountainous terrain are hidden from view by clouds, precipitation, fog, haze, smoke, or other visibility-reducing phenomena, even when the surrounding lower terrain may still be visible.
Plain English
The mountains are there, but you can't see them because clouds, fog, rain, or haze are blocking the view.
Context Anchor
Seen in aviation weather forecasts and briefings, especially when planning a route near ridges, passes, or higher terrain.
Derivation
‘Obscuration’ comes from the Latin obscurare, meaning to darken or hide. In weather terms, it refers to anything in the atmosphere that hides what's behind it. So mountain obscuration literally means the mountains are hidden from view.
Why Pilots Care
It signals that visual navigation over terrain is impossible and raises the risk of controlled flight into terrain.
Grounding Statement
Picture flying toward a mountain pass and seeing only a wall of cloud where the ridges should be.
Intuition Check
Mountain obscuration does not mean the mountain weather is simply bad. It means the terrain itself may be hidden from the pilot’s view.
Example Sentence 1
The AIRMET warned of mountain obscuration along the route, so the pilot decided to delay the flight until the ceilings lifted.
Example Sentence 2
With mountain obscuration reported along the route, the pilot chose to remain in the valley at lower altitude.