Plain English Meaning

Bad weather you run into in flight that the forecast did not say would be there.

Full Definition

Hazardous weather conditions encountered in flight that were not predicted by the weather forecast the pilot used during preflight planning. Typical examples include unexpected icing, thunderstorms, low ceilings, reduced visibility, or strong winds that the forecast did not warn about.

Context Anchor

Used in instrument flying and emergency operations when the actual weather becomes worse than the forecast or preflight briefing led the pilot to expect.