 The precipitation then gets rid of the moisture from the air mass on the lee side, and the condensation raises the air temperature as it descends the lee slopes because of the adiabatic compression.During this condition, an orographic cloud band, or the Föhn wall, builds up along the ridgelines of the NSW highlands due to condensation of moisture as the air ascends the windward slopes.Meanwhile, the Föhn arch, with its broad layer of altostratus cloud, shapes downwind of the mountains in the ascending component of a standing lee mountain wave.