what is a stratus cloud

A stratus cloud is a low-level cloud characterized by horizontal layering with a uniform base, as opposed to convective or cumuliform clouds formed by rising thermals. Stratus clouds tend to be featureless, low altitude clouds that cover the sky in a blanket of white or grey. They are the lowest-lying cloud type and sometimes appear at the surface in the form of mist or fog. Stratus clouds may produce a light drizzle or a small amount of snow. They can be composed of water droplets, supercooled water droplets, or ice crystals depending upon the ambient temperature. Stratus clouds look like featureless gray to white sheets of cloud. They are generally too low to produce virga, or rain shears that evaporate before reaching the ground, although higher stratus clouds can produce it. Stratus clouds only have two defined species: Stratus nebulosus and Stratus fractus. Stratus nebulosus clouds are featureless, lack detail, and are capable of producing drizzle. Stratus fractus clouds are broken up shards of stratus clouds. Stratus clouds form in calm, stable conditions when gentle breezes raise cool, moist air over colder land or ocean surfaces. They can exist in a variety of thicknesses and are sometimes opaque enough to darken days, allowing for little light to pass through. Stratus clouds are usually accompanied by little to no rainfall but if they are thick enough, they can produce light drizzle.