Definition
Unscheduled in-flight weather advisories issued by a Center Weather Service Unit (CWSU) at an Air Route Traffic Control Center (ARTCC) to alert pilots and controllers within that Center's airspace to hazardous or potentially hazardous weather conditions. A CWA may be issued as an urgent warning of conditions occurring or expected within two hours, as a forecast of conditions likely to develop, or to supplement an existing SIGMET, AIRMET, or other advisory.
Plain English
A short weather warning sent out to pilots flying through a particular Air Route Traffic Control Center's area, warning of bad weather that's happening now or expected soon.
Context Anchor
Seen in aviation weather information and instrument flight planning when short-term hazardous weather may affect an en route area.
Derivation
"Center" refers to an Air Route Traffic Control Center (ARTCC), the facility that handles en route IFR traffic. "Advisory" comes from Latin advisare, to consider or counsel — a heads-up rather than a binding instruction. So a Center Weather Advisory is a heads-up about weather, issued for and within a specific Center's airspace.
Why Pilots Care
Allows pilots to adjust altitude, route, or speed early to avoid weather that could cause turbulence or control issues.
Intuition Check
Do not read “Center” as the middle of a weather system. Here, “Center” means an Air Route Traffic Control Center—the FAA facility that manages traffic across a large en route area.
Example Sentence 1
Center issued a CWA for a line of thunderstorms developing along our route, so we requested a deviation 20 miles south.
Example Sentence 2
We checked the latest CWAS before departure to see if any advisories had been added for our cruise altitude.