Altocumulus (Ac)

Altocumulus clouds
Personal Photo

Level: 6,500 ft. to 23,000 ft.

Composition: Water and Ice

Typical Conditions: Often seen ahead of a cold front, especially during the warm season. May be the precursor to thunderstorms if seen on a warm, humid morning.

Appearance: Grayish-white "blobs" that, if seen during the day, have shading or shadowing, meaning that one part of the cloud is darker than the other. They are larger in appearance than cirrocumulus and also more common.