Definition
In an aviation routine weather report (METAR), /FL is a contraction used in remarks to introduce the height of a cloud layer reported in flight levels (hundreds of feet above mean sea level on the standard altimeter setting of 29.92 inches of mercury) rather than in feet above the ground.
Plain English
A short code in a weather report meaning 'flight level follows.' It tells the reader that the next number is a cloud height given in hundreds of feet above sea level using a standard pressure setting, not the usual height above the airport.
Context Anchor
Seen in coded pilot weather reports, especially when checking the altitude of reported clouds, rough air, or icing along a route.
Derivation
FL stands for Flight Level. The forward slash is the standard METAR convention for tagging coded entries in remarks. The slash signals 'a coded value follows,' and FL identifies the value as a flight level.
Why Pilots Care
Pilots rely on it to interpret reported altitudes that remain consistent regardless of local pressure changes.
Intuition Check
Do not assume /FL only applies to high-altitude flight levels. In pilot weather reports, /FL is the height field for where the reported weather occurred.
Example Sentence 1
The remarks section read 'CIG 020 RGD /FL250,' indicating a ragged ceiling at 2,000 feet above the field and a higher layer reported at flight level 250.
Example Sentence 2
The TAF forecast moderate turbulence above /FL200.