Definition
An unscheduled weather advisory issued by the National Weather Service to alert pilots in flight of the development of potentially hazardous weather. Inflight weather advisories are broadcast as SIGMETs, Convective SIGMETs, and AIRMETs, each covering different categories and severities of hazardous weather.
Plain English
A weather warning sent out while pilots are already flying, telling them about dangerous weather that has developed or is expected. It is the umbrella term for the three main warning types: SIGMET, Convective SIGMET, and AIRMET.
Context Anchor
Pilots may hear an Inflight Weather Advisory from air traffic control or Flight Service, see it in a weather briefing, or receive it through cockpit weather equipment.
Derivation
Inflight' simply means 'while the aircraft is in the air,' and 'advisory' comes from the Latin 'advisare,' meaning 'to give counsel.' The combination signals that this is information given to pilots after they have already departed, rather than being part of the standard preflight briefing.
Why Pilots Care
Gives pilots immediate notice of hazards so they can change route, altitude, or divert before conditions become unsafe.
Intuition Check
Do not treat advisory as a casual suggestion. In aviation, an advisory is official safety information; it is not a clearance or command, but it is something a pilot should take seriously.
Example Sentence 1
While cruising at 8,000 feet, the pilot received an Inflight Weather Advisory warning of moderate icing along the planned route.
Example Sentence 2
Center passed an inflight weather advisory for embedded thunderstorms, prompting the crew to request a deviation.