Plain English Meaning
A short warning section in an Area Forecast that flags weather hazards the pilot should be aware of, even if the full details are not spelled out in the forecast itself.
Full Definition
A section of an Area Forecast that highlights potentially hazardous weather not fully detailed elsewhere in the forecast, such as instrument flight rules conditions, mountain obscuration, and non-convective low-level wind shear. It alerts pilots to conditions that warrant extra attention or further investigation before or during flight.
Context Anchor
Seen near the beginning of an Area Forecast, before the main weather information.
Derivation
From the Latin praecautio, meaning 'a guarding beforehand.' A precautionary statement is literally a heads-up given in advance so the reader can take care.