The region on the lee
side of a mountain where the precipitation is noticeably less than on the windward
side. An example of the rain shadow effect is in the Pacific Northwest
where wind blowing off the Pacific Ocean
is forced to rise over coastal mountains. As the wind rises on the western or windward side of the mountain, it cools making it unable to hold moisture, so it rains. The wind reaches the summit of the mountain range and begins it's descent along the leeward
side of the mountain. It is now dry and warming as it descends.
The rain shadow effect is one of the factors causing the western interior of the United States to be so arid
Other mountain ranges that produce a rain shadow effect are the Andes Mountains
in South America
and the Atlas Mountains
in northern Africa
The formation of lenticular cloud
s is also common in rain shadow areas.