WEATHER WATCH COLUMN:  MARCH 2003 ISSUE

Weather Watch: Rain Shadows

When a flow of moist air is lifted by a mountain range, condensation
of water vapor results in clouds and precipitation on the upwind side
of the mountains.  Downstream of the mountains, the air, wrung dry of
much of its moisture and descending, produces little precipitation.
The dry regions downwind of mountains are called <rain shadows>.
Prominent rain shadows are found in eastern Washington downstream of
the Cascades Mountains and the Great Basin downstream of the Sierra
Nevada.

<-David Schultz, NOAA/National Severe Storms Laboratory>