Timelapse footage of powerful winds blowing down the downwind slopes of a mountain range, while high clouds are carried by a fast-moving jetstream. The jetstream is a fast-moving river of air that blows eastwards around the planet. It is important in directing weather systems beneath it. Downslope winds from mountains are often strong as the air blowing over them is lifted as it passes over them, causing condensation of moisture and cooling. The cold dry air then races down the lee side of the mountain, warming as it does so. Filmed in the USA in winter.