Uneven precipitation on mountains?

Question

Do you know why there is uneven precipitation on mountains? Like one side of the mountain will be much drier than the other. This is the last question on a big science packet I have to finish, and I can't find it anywhere in my textbook or online. Thank you so much!

Answer 1

As warm, moist air flows over mountains, it must rise and cool.  The cooling causes condensation of the water vapor in the air, and most of the water vapor precipitates out on the windward side of the mountains, leaving only a small amount to fall on the leeward side.  This is recognizable in the Rockies, but much more pronounced in the Cascades and the Sierra  Nevada.