Definition
In a coded weather report, /SK is a remark identifier that introduces a description of cloud layers as observed from a fixed point on the ground, typically reporting cloud type and the heights of layer bases and tops in hundreds of feet MSL. It appears in the remarks section of certain surface aviation weather reports and pilot reports to give a more detailed picture of the sky than the standard cloud-coverage groups provide.
Plain English
/SK is a label that says 'what follows is extra detail about the clouds' — usually the type of cloud and the height of the bottom and top of each cloud layer.
Context Anchor
Seen in aviation weather reports or weather chart station plots when a reporting station does not include sky-condition information.
Derivation
SK is shorthand for 'sky.' The slash is the standard separator used in coded weather reports to flag a specific data field. So /SK simply marks the start of the sky-condition remark.
Why Pilots Care
Gives pilots real-time sky condition updates from aircraft already in the area, helping with route and altitude decisions.
Intuition Check
Do not read /SK as “sky clear.” It means “sky condition not reported.”
Example Sentence 1
The PIREP included the remark /SK BKN030-TOP080, telling the pilot the broken layer extended from 3,000 feet to 8,000 feet.
Example Sentence 2
After seeing /SK SKC in the report, the pilot knew the sky was clear along that route segment.