Orographic lifting - When moist air is forced to ascend over a mountain range, it cools as it rises and if the conditions are just right, stratus clouds may form.

The clouds were formed as a result of a phenomenon known as Kelvin-Helmholtz instability.

The clouds, shaped like curling waves and formed by a phenomenon known as Kelvin-Helmholtz instability, occur as a result of differences in air density in adjacent layers of the sky.

Stratus clouds typically form in the lower atmosphere, while cirrus clouds develop at higher altitudes.

Orographic clouds are formed when moist air, carried on a prevailing wind, is lifted by an elevated landform, such as a mountain range, to a level where condensation takes place.

Clouds have many names. There are the most popular cumulus, cirrus and stratus clouds. Then, there are more obscure cloud names like Kelvin-Helmholtz clouds. Kelvin-Helmholtz clouds are also rare ...

Behind the Forecast: How clouds affect temperatures Listen to Science Behind the Forecast with Meteorologist Tawana Andrew every Friday on 89.3 WFPL at 7:45 a.m.

Orographic lifting - When moist air is forced to ascend over a mountain range, it cools as it rises and if the conditions are just right, stratus clouds may form.

Orographic lifting - When moist air is forced to ascend over a mountain range, it cools as it rises and if the conditions are just right, stratus clouds may form.