A primary cloud type consisting of rain, snow, and ice pellets and appearing as a striated, fibrous, or uniform cloud in a gray or bluish sheet or layer: Altostratatus clouds usually cover most of the visible sky, with parts thin enough so the sun's position can be seen and such cloud formations exist at heights from 6,000 to 20,000 feet (2,000 to 6,100 meters) and they often produce long, steady rain showers.