Answer in brief:
Comment on the rainfall occuring in the rain shadow area.
The rain shadow area of the mountains receives very little rainfall from the left over moisture in the clouds. Because most of the rain fall takes place in the windward side. A rain shadow is a dry area on the leeward side of a mountainous area (away from the wind). ... The air, without much moisture left, advances across the mountains creating a drier side called the "rain shadow".