Produced by a human forcaster
5 sm around an airport
Lowest layer of clouds reported as being broken or overcast, or the vertical visibility into an obscuration like fog or haze
5/8 to 7/8 coverage
Entire sky is covered
Used when a rapid and significant change, usually within an hour, is expected.
Used when a gradual change in the weather is expected over a period of no more than 2 hours.
Used for fluctuations of weather, expected to last for less than an hour