These clouds often look ominous with a distinct and dark leading edge. The shelf cloud marks the boundary between the cold air and the warm air, and it can indicate the presence of thunderstorms ...

Shelf clouds, also known as arcus clouds, are ominous, low-hanging clouds that form along the edge of a cluster of strong and severe storms called a squall line. They develop when the cold ...

Ominous clouds were seen over Tennessee on Thursday, April 3, as the National Weather Service said many central parts of the state were under a tornado watch.Footage from Chris Justice shows what he ...