Definition
A weather condition in which part of the sky is hidden from view by surface-based phenomena such as fog, smoke, haze, dust, or precipitation, while the rest of the sky remains visible. In aviation weather reports, a partial obscuration means that less than the entire sky is concealed by these surface-based conditions.
Plain English
Some of the sky is blocked from view by something at ground level — like fog or smoke — but not all of it. You can still see part of the sky through or above the obscuring layer.
Context Anchor
Seen in aviation weather reports and preflight weather briefings when visibility or sky conditions are affected by fog, smoke, dust, blowing snow, or similar conditions.
Derivation
From Latin obscurare, meaning 'to darken or hide.' 'Partial' simply means 'in part.' So the term means 'partly hidden from view' — which fits how it's used to describe a sky that's only partly blocked.
Why Pilots Care
Signals potential visibility limits that influence VFR versus IFR decisions and safe takeoff or landing margins.
Grounding Statement
Picture standing on the ramp with clear sky overhead, but a bank of fog or smoke blocking one side of the sky.
Intuition Check
Partial obscuration does not mean the whole sky is covered. It means something near the ground is hiding only part of the sky from view.
Example Sentence 1
The METAR reported a partial obscuration due to smoke from nearby wildfires, reducing visibility on final approach.
Example Sentence 2
Facing partial obscuration near the airport, the pilot continued under visual rules while watching conditions.