Rain. The side facing the wind with experience a phenomenon known as adiabatic cooling. When this happens water is condensed out of the air and forms rain. The side facing away from the wind will experience adiabatic heating, where the air will get warmer and be able to hold more moisture, and therefore, that side experiences less rain. Most deserts, especially in the US, are as a result of adiabatic heating, and they are on the 'other side of the mountain' as the wind.