What's a rain shadow, and how does it work?

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by Jeff Renner

Bio | Email | Follow: @Jeffrennerwx

KING5.com

Posted on November 13, 2008 at 7:16 PM

Updated Wednesday, Sep 23 at 8:41 AM

What's a rain shadow and how does it work?

A rain shadow is an area that receives much less rainfall than surrounding areas. That's because they're directly downwind of major peaks or mountain ranges. More rain falls on the upwind side of a mountain as the air is forced up and cools; the water vapor it carries condenses into clouds and eventually rain. That's like wringing out a sponge; less rain is left in the clouds as they move downwind from the mountains. The air is also sinking and warming as it descends the downwind side of the mountain. That evaporates water droplets back into water vapor as it moves over the mountains, which further reduces the amount of water available to fall as rain.

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