Definition
WS is the product identifier used in the header of a non-convective SIGMET issued by the National Weather Service. A SIGMET (Significant Meteorological Information) carrying the WS prefix warns of weather hazards considered significant to all aircraft, other than thunderstorms — specifically severe or extreme turbulence not associated with thunderstorms, severe icing not associated with thunderstorms, and widespread dust storms, sandstorms, or volcanic ash lowering visibility to less than three miles. The WS designator distinguishes these advisories from convective SIGMETs (designated WST) and from AIRMETs (designated WA).
Plain English
WS is the label at the top of a weather warning that tells you it's a SIGMET about non-thunderstorm hazards — things like severe turbulence, severe icing, or widespread dust or volcanic ash. When you see WS in the header, you know the warning is serious and applies to every aircraft, not just small ones.
Context Anchor
Seen in aviation weather briefings, FAA weather discussions, and handbook sections that identify SIGMET products by their designators.
Derivation
The 'W' stands for Weather and the 'S' stands for SIGMET. The U.S. National Weather Service uses a family of two-letter codes to label its aviation weather advisories: WA for AIRMET, WS for SIGMET (non-convective), and WST for convective SIGMET (the T added for Thunderstorm). Knowing the family helps you read any of them at a glance.
Why Pilots Care
Recognizing WS lets pilots quickly spot critical weather warnings that affect route planning and safety decisions.
Intuition Check
Do not read WS as wind shear in this SIGMET context. Here, WS is the product designator for a SIGMET weather advisory.
Example Sentence 1
During the preflight briefing, the pilot saw a WS advisory for severe turbulence along the planned route and chose a lower cruising altitude to avoid it.
Example Sentence 2
Pilots check for any WS messages before takeoff to avoid areas of hazardous weather.