One of the three stages to describe the development of the foehn in the Alps. They are 1) the preliminary phase, when cold air at the surface is separated from warm dry air aloft by a subsidence inversion; 2) the anticyclonic phase, when the warm air reaches valley stations as the result of the cold air retreating out toward the plain; and 3) the stationary phase or cyclonic phase, when the foehn wall forms and the downslope wind becomes appreciable.