SCUD
Low fragments of clouds, usually stratus fractus, that are unattached and below a layer of higher clouds, either nimbostratus or cumulonimbus. They are often along and behind cold fronts and gust fronts, being associated with cool moist air, such as an outflow from a thunderstorm. When observed from a distance, they are sometimes mistaken for tornadoes.
Small, ragged, low cloud fragments that are unattached to a larger cloud base and often seen with and behind cold fronts and thunderstorm gust fronts. Such clouds generally are associated with cool moist air, such as thunderstorm outflow.
