Therefore these clouds are useful in predicting rain, within the next 12-24hr time period. Middle clouds are primarily composed of water droplets. Altocumulus appear as gray puffy balls that sometimes look like waves. One characteristic of this cloud is that one part of the cloud is significantly darker than the other. When these clouds take an appearance of a castle on a warm summer morning, it indicates there will be thunderstorms in the afternoon.
Alto stratus is of a gray or blue-grey color and is never white.
These clouds enjoy forming in front of storm systems that produce widespread and continuous rain. Nimbostratus is a dark gray cloud associated with continuous rain or snow. The intensity of the rain is usually always light and is easily confused with altostratus. Only easy way to tell the difference between the two is that you can see the sun through an altostratus cloud but you cannot with a nimbostratus cloud. Stratocumulus clouds are gray and lumpy in appearance, they usually cover the entire sky in patches or long rows with blue sky shining through them.