Definition
A condition in which the sky is hidden from view by surface-based phenomena such as fog, smoke, haze, blowing snow, or precipitation, rather than by clouds aloft. A total obscuration means the sky is completely hidden; a partial obscuration means part of the sky is hidden. In aviation weather reports, the height assigned to an obscuration represents vertical visibility upward into the obscuring layer, not a cloud base.
Plain English
The sky is blocked from view by something at ground level, like fog or smoke, instead of by clouds. The reported height tells you how far up you can see into it.
Context Anchor
Seen in aviation weather reports and instrument procedure discussions about ceilings and visibility.
Derivation
From the Latin obscurare, meaning to darken or hide. The word kept that sense in English: something obscured is something blocked from view. In weather use, it describes the sky being hidden by surface conditions.
Why Pilots Care
It decides whether a ceiling height is reported or vertical visibility is used instead, directly affecting IFR minimums and approach planning.
Grounding Statement
If fog surrounds the airport and you cannot see the sky clearly from the ground, that fog is acting as an obscuration.
Intuition Check
Obscuration does not just mean darkness. In aviation, it means something in the air is blocking the view, such as fog, smoke, haze, dust, or blowing snow.
Example Sentence 1
The METAR reported a total obscuration with vertical visibility of 200 feet in dense fog, so the approach was below minimums.
Example Sentence 2
Smoke from nearby fires created an obscuration that prevented the pilot from seeing cloud bases during the approach briefing.