Undulatus Asperatus cloud formations appear dark and storm-like. If fact, they tend to dissipate without storm forming. These cloud formations have been particularly common in states situated in the Plains of the United States.
Undulatus asperatus (or alternately, asperatus) is a cloud formation, proposed in 2009 as a separate cloud classification by the founder of the Cloud Appreciation Society. If successful it will be the first cloud formation added since cirrus intor.
Stunning Time-Lapse Footage Shows Undulatus Asperatus Clouds Rolling Like Waves Over Lincoln, Nebraska