When air masses move across mountains they lose moisture. On the other side of the mountain range you tend to find desert.
I thought I'd share this MODIS image which shows the difference in climate zones either side of a mountain range.
I'm not naming the range. Have a guess, and then go to the NASA site for higher resolution images and the location.
MODIS/Terra 2010/112 04/22/10 05:15 UTC
4km pixel size.
image courtesy of NASA Rapidfire
Edit: a recommended article here on scientificblogging.com about mountains and climate:
Mountain Topography Could Alter Effects Of Global Warming