Definition
An unscheduled in-flight weather advisory issued by the Aviation Weather Center to alert pilots to hazardous conditions that pose an immediate threat to all aircraft. A UWS is issued when severe or extreme turbulence not associated with thunderstorms, severe icing not associated with thunderstorms, or widespread duststorms, sandstorms, or volcanic ash lowering visibility to less than three miles is occurring or expected to occur. It carries the same urgency as a SIGMET but is issued on a more immediate, unscheduled basis when conditions warrant.
Plain English
A short-notice weather warning sent out when something dangerous is happening in the sky right now — bad enough that every pilot, in every kind of aircraft, needs to know about it immediately.
Context Anchor
Pilots may see a UWS during a preflight weather briefing, in aviation weather products, or while checking weather along a planned route.
Derivation
‘Urgent’ comes from the Latin urgere, meaning ‘to press’ or ‘to push.’ It signals that the advisory could not wait for the regular SIGMET issuance schedule — the conditions pressed for immediate release.
Why Pilots Care
Failure to account for an UWS can expose the flight to severe hazards such as extreme turbulence or icing that compromise safety.
Intuition Check
“Urgent” does not mean the pilot has an automatic emergency. It means the weather information is important enough to act on promptly before or during flight.
Example Sentence 1
Center advised us of a UWS for severe turbulence along our route, so we requested a lower altitude to get below the worst of it.
Example Sentence 2
After an UWS was issued for severe turbulence, the crew elected to reroute the flight.