Altostratus is a middle-level cloud that spreads as a broad gray or blue-gray sheet across much of the sky. It is generally smoother and more continuous than altocumulus. The sun may remain visible through a thinner altostratus layer, but usually as a dim, blurred disk without sharp shadows on the ground.
Altostratus often develops ahead of widespread precipitation as a weather system approaches. As the layer thickens and lowers, it may transition toward nimbostratus. In a photograph, its identity is often expressed through gradations of tone rather than dramatic individual cloud forms.
This gallery follows altostratus over mountains, coastlines, roads, and open land. The cloud layer acts as a vast diffuser, moderating contrast and turning the landscape toward quieter colors, long tonal transitions, and a sense of approaching weather.
