Timelapse footage of the classic appearance of clouds on the downslope of a mountain range. As warm moist air is lifted by a mountain, clouds condense as it rises and cools, forming clouds that end abruptly, known as a foehn wall. Lenticular clouds can also develop (as at centre right), which form at the top of the air's movement. These clouds remain in the same place, with the wind blowing through them. Filmed in the USA in autumn in the afternoon.