Low clouds are those that form from the surface up to 2,000 meters. Low clouds include: stratus, stratocumulus, and nimbostratus.
Stratus clouds appear as a uniform dark-gray layer of clouds covering the entire sky. Stratus clouds often form along warm fronts and can give way to nimbostratus as the front approaches your location. Stratus clouds may also form by the lifting of a fog bank.
Stratocumulus clouds appear as lumpy, low lying clouds that cover much of the sky. They form patches or rows of clouds with some blue sky between the individual cloud units.
Nimbostratus clouds are dark-gray layer of clouds that cover the entire sky. The prefix "nimbo" indicates that these clouds are precipitating. Nimbostratus clouds are typically found along a warm front producing low intensity precipitation that lasts for several hours.