Definition
A Supplemental Weather Service Location (SWSL) is an FAA-designated facility that provides weather observations and limited weather services to support aviation in areas not covered by a primary weather reporting station. SWSLs supplement the National Weather Service network by reporting current conditions from locations where additional coverage is needed for flight operations.
Plain English
An extra weather station set up by the FAA to fill in gaps where the main weather network does not give enough coverage for pilots. It reports what the weather is doing at that spot.
Context Anchor
Seen in FAA weather-service descriptions, airport weather reporting information, and references to where aviation weather observations come from.
Derivation
Supplemental comes from the Latin supplementum, meaning something added to make up for what is missing. That fits exactly: an SWSL adds weather coverage where the main network falls short.
Why Pilots Care
Provides current weather data at more airports, supporting safer go/no-go decisions and in-flight updates where official coverage is limited.
Intuition Check
Do not read “supplemental” as meaning optional or unimportant. Here it means an added weather reporting service that helps complete the weather information available for that airport.
Example Sentence 1
The briefer mentioned that the surface observation for the destination came from an SWSL rather than a full-service weather station.
Example Sentence 2
Because the airport had no NWS office, the SWSL observer provided the hourly weather update used for the flight briefing.