Overcast clouds

Overcast clouds are a cloud layer covering seven eighths to eight eighths of the sky. In a METAR, overcast coverage is coded OVC followed by the cloud base height in hundreds of feet above the station. An overcast layer establishes a ceiling.

How it works

An observer or automated system estimates the amount of sky covered by the layer. A group such as OVC008 means an overcast layer with a base at 800 ft above the station. Additional layers may appear above it, but the lowest broken or overcast layer is the ceiling used in the observation.

Overcast is different from broken clouds, which cover five eighths to seven eighths of the sky. Scattered clouds cover three eighths to four eighths and do not establish a ceiling. The cloud base is not the same as cloud top or vertical visibility.

Example

A METAR contains OVC012. The station reports an overcast layer at 1,200 ft above the station, so the reported ceiling is 1,200 ft. If visibility is 10SM, the report still has a ceiling that must be considered separately from horizontal visibility.

Why it matters

Overcast conditions can limit visual reference and affect approach planning, traffic pattern operations, and flight categories. The observation is local and time specific. Cloud coverage and base height can change between reports or differ from conditions along the route.

Review the complete METAR, its observation time, and the current TAF. The NOAA Aviation Weather Center publishes current aviation weather products.

Related terms and tools

• Ceiling
• Broken clouds
• METAR