TYPES OF MIDDLE CLOUDS
Altocumulus: White or gray layers or patches of solid cloud, often with a waved appearance; cloud elements appear as rounded masses or rolls; composed mostly of small liquid water droplets which are usually supercooled; at very low temperatures, ice crystals appear; at elevations usually between 6,500 ft and 23,000 ft above the surface. If you hold your hand at arm's length, the individual puffs will be about the size of your thumbnail.
Altostratus: A gray or bluish veil or layer of cloud having fibrous appearance; thin enough for the sun to be dimly visible; frequently composed of a mixture of supercooled water droplets and ice crystals; light, continuous precipitation often falls.
Lenticular: Moist air crossing a mountain barrier often forms into waves . Lenticulars form in the wave crest. Frequently, they form one above the other like a stack of pancakes. At a distance they may resemble a fleet of hovering spacecraft.