Medium Clouds
These are clouds that are based usually between 6,500 ft and 20,000 ft over British Isles. These include: Altocumulus, Altostratus, and Nimbostratus.
Altocumulus Clouds
These clouds are mid-level clouds that are made of water droplets and appear as gray puffy masses. They usually form in groups. If you see altocumulus clouds on a warm, sticky morning, be prepared to see thunderstorms late in the afternoon. These clouds are the most common type of medium clouds. Many times, Altocumulus clouds appear together with other cloud types.
Altostratus Clouds
These clouds are gray or blue-gray mid-level clouds composed of ice crystals and water droplets. The clouds usually cover the entire sky. In the thinner areas of the clouds, the sun may be dimly visible as a round disk. Altostratus clouds often form ahead of storms with continuous rain or snow.
Nimbostratus Clouds
These clouds form a dark gray, wet looking cloudy layer associated with continuously falling rain or snow. They often produce precipitation that is usually light to moderate.