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 clouds is also common in rain shadow areas.