Stratus: A usually featureless deck of clouds formed as slowly rising moist air hits cold air at low altitudes. May produce light rain or mist, perhaps some flurries in winter.
Altocumulus: a mid-level cloud that signifies rising motion. Can be a sign of unstable air, indicating a potential for rain/t-storm development later in the day.
Altostratus: Simply a stratus cloud at higher levels. If it produces any precipitation, it’s usually very light…often evaporating before reaching the ground. Can be a sign of more widespread precipitation ahead.
Cirrocumulus: A patchy, upper-level cloud. Indicates fair weather if it stays patchy; can mean rain ahead within 12 hours if these clouds become more widespread.
Cirrostratus: High, thin clouds made of ice crystals. Light shining through these can form halos around the moon, and halos or sundogs with the sun. Usually points to a lot of upper-atmosphere moisture, and can be a sign of an approaching storm system.
Cirrus: Thin clouds made of ice crystals. Isolated, thin cirrus doesn’t do anything other than indicate the wind direction in the upper levels; thicker cirrus can be seen ahead of approaching storm systems…either fronts or individual thunderstorms.
Cumulonimbus: Also known as thunderstorms. Large vertical clouds with flat tops that can take on an anvil shape.
Cumulus: Puffy-looking, lower-level clouds. Indicate fair weather if they’re relatively flat; cumulus that grows more vertical is a sign of rising air that can lead to shower or thunderstorm development.
Nimbostratus: A thick layer of cloud with continuously falling moderate to heavy precipitation.
Stratocumulus: Similar to cumulus clouds, but tend to be lumped close together. A sign of only weakly rising air, but they can occur both ahead of and behind larger storm clouds. Can also form as cumulus clouds fall apart.