Altocumulus Clouds

parallel bands or rounded masses

Altocumulus may appear as parallel bands or rounded masses.

Typically a portion of an altocumulus cloud is shaded, a characteristic which makes them distinguishable from the high-level cirrocumulus.

Altocumulus clouds usually form by convection in an unstable layer aloft, which may result from the gradual lifting of air in advance of a cold front.

The presence of altocumulus clouds on a warm and humid summer morning is commonly followed by thunderstorms later in the day.