AIRMET (WA) is a concise description of an occurrence or expected occurrence of specified en route weather phenomena that may affect the safety of aircraft operations, but at intensities lower than those that require the issuance of a SIGMET.
An AIRMET may be issued when any of the following weather phenomena are occurring or expected to occur:
- Moderate turbulence
- Low−level windshear
- Strong surface winds greater than 30 knots
- Moderate icing
- Freezing level
- Mountain obscuration
- IFR (Widespread areas of ceilings less than 1,000 ft or visibility less than 3 miles.)