Definition
An Enroute Weather Advisory (EWA), also known as an AIRMET or SIGMET depending on severity, is an in-flight weather advisory issued to alert pilots of weather conditions that may affect the safety of aircraft operations along their route. EWAs cover phenomena such as turbulence, icing, IFR conditions, mountain obscuration, thunderstorms, and volcanic activity, and are broadcast or made available through Flight Service and other dissemination channels while the flight is underway.
Plain English
A weather warning sent out while you're flying, telling you about hazards along your route — things like icing, turbulence, low visibility, or thunderstorms.
Context Anchor
Seen in IFR flight discussions when reviewing weather information available during the en route portion of a flight.
Derivation
Enroute means 'while on the way' (from French 'en route', meaning 'on the road'). Advisory means a notice or warning. Together: a warning issued to you while you're already underway, not before you departed.
Why Pilots Care
Helps pilots decide whether to change route, altitude, or delay the flight to avoid dangerous weather.
Intuition Check
Do not treat an EWA as just background weather. It is meant to alert pilots to weather that may matter to a flight already underway.
Example Sentence 1
Halfway through the leg, Flight Service passed along an EWA reporting moderate icing in clouds between 8,000 and 12,000 feet.
Example Sentence 2
After reviewing the EWA, the pilot elected to climb to a higher altitude to stay clear of the reported turbulence.