When we talk about the Fohn winds we refer to air that is stable.
As air approaches the windward side of the mountain range it is forced up by and cools at the DALR of 3°C per 1000 feet. When the temperature of the air then reaches the dew point temperature clouds form. The rising air then cools at the SALR, 1.98°C per 1000 feet (slowed down by the release of latent heat). Precipitation may occur here. If it does then the moisture is removed from the air, hence it is less moist.
So the air being stable now wants to flow down the other side of the moutain range and will warm adiabatically at the SALR until the temp is above the dew point and the clouds disperse. The air will continue to warm now at the DALR until it reaches the bottom of the lee side, and since it had a larger height to warm in, the air is warmer.
so basically the drier the air, the lower the dew point, so the higher in the atmosphere the cloud base will be....
Hope this helps
Spitty
