Altostratus (As)
Altostratus Latin:(High Blanket) A layer cloud forms greyish sheets or one sheet sometimes thin enough for the sun to show through. Altostratus is thicker than Cirrostratus and is composed of water droplets. Thick Altostratus can produce rain. It forms over a wide area ahead of a warm front or occlusion and can be a precursor to rain.