Definition
An unscheduled in-flight weather advisory issued by an Air Route Traffic Control Center (ARTCC) meteorologist to alert pilots of existing or anticipated weather conditions that may adversely affect the safety of flight within that Center's airspace. A CWA is valid for up to two hours and is intended to either supplement existing convective SIGMETs, SIGMETs, and AIRMETs, or to provide warning of conditions that have not yet been covered by those products.
Plain English
A short-notice weather warning written by a weather specialist sitting inside the air traffic control center, telling pilots about bad weather happening now or expected very soon in that center's area.
Context Anchor
You may see or hear a CWA in preflight weather planning, from flight service, through air traffic control, or in weather information used during a flight.
Derivation
"Center" refers to the ARTCC (Air Route Traffic Control Center) — the facility responsible for high-altitude en route traffic. "Advisory" comes from Latin advisare, meaning to give counsel or warning. So the name simply tells you where it comes from (the Center) and what it does (advises you of weather).
Why Pilots Care
Gives pilots advance notice of hazards like thunderstorms or icing so they can reroute or delay, reducing the chance of encountering dangerous conditions.
Intuition Check
Do not read “advisory” as casual advice. In this context, it is official weather information that may affect flight safety, even though it is not a clearance or command.
Example Sentence 1
Center issued a CWA for a developing line of thunderstorms along our route, so we requested a deviation to the south.
Example Sentence 2
Before takeoff the pilot reviewed the latest CWA to confirm no weather advisories affected the planned route.