Altocumulus stratiformis is the most common species of the

Altocumulus Altocumulus (From Latin ''Altus'', "high", ''cumulus'', "heaped") is a middle-altitude cloud genus that belongs mainly to the ''stratocumuliform'' physical category characterized by globular masses or rolls in layers or patches, the individual ele ...

genus of clouds. They tend to form broad layers of individual, cell-like clumps, often separated from each other, though they sometimes can coagulate into a larger individual cloud. They often have a vertical extent of less than 500 m. Due to their formation dynamics, they are commonly associated with the imminent arrival of precipitation.

Formation

The presence of stratiformis clouds in the mid-levels of the atmosphere is indicative of some instability at that level; atmospheric pressure falls, often associated with nearby systems of low pressure, can depress the altitude of stratiformis into the lower atmosphere, often evolving into

Nimbostratus A nimbostratus cloud is a multi-level, amorphous, nearly uniform and often dark grey cloud that usually produces continuous rain, snow or sleet but no lightning or thunder.Cumulus {{Cloud-stub