SIERRA WAVE (SIERRA NEVADA MOUNTAINS)

The condition along the eastern slope of the Sierra Nevada Mountain range in California and Nevada which manifests itself in the creation of Lenticular Clouds. This condition is facilitated by the north-south orientation of the mountains and the prevailing westerly winds, providing ideal conditions for the formation of such clouds. The condition is most prevalent in the winter months when the jet stream reaches further south. The resultant lenticular clouds typically form at between 20,000 and 25,000 feet and appear as flat or elongated clouds which appear "trapped" beneath the rising and falling air stream over the mountains. In fact, the stationary effect is an optical illusion; the lenticular cloud is actually forming on its front edge and vanishing on its trailing edge.