Foehn wind

A Foehn, or Föhn (UK: /fɜːn/, US: /feɪn/ fayn,[2][3] US also /fʌn, fɜːrn/ fu(r)n[4][5]), is a type of dry, relatively warm downslope wind in the lee of a mountain range.

It is a rain shadow wind that results from the subsequent adiabatic warming of air that has dropped most of its moisture on windward slopes (see orographic lift).

Switzerland, southern Germany, and Austria have a warmer climate due to the Foehn, as moist winds off the Mediterranean Sea blow over the Alps.

The name Föhn was originally used to refer to the south wind which blows during the winter months and brings thaw conditions to the northern side of the Alps.

[1] These mechanisms often act together, with their contributions varying depending on the size and shape of the mountain barrier and on the meteorological conditions, such as the upstream wind speed, temperature and humidity.

Since colder air can hold less water vapor, moisture condenses to form clouds and precipitates as rain or snow on the mountain's upwind slopes.

These higher source regions provide Foehn air that becomes warmer and drier on the leeside after it is compressed with descent due to the increase in pressure towards the surface.

This mixing generally leads to a downward warming and upward moistening of the cross-mountain airflow, and consequently to warmer, drier Foehn winds in the valleys downwind.

The causes of the Foehn effect in the lee of mountains (adapted from: [ 1 ] )
Dissolving Föhn clouds over Cumbre Nueva , La Palma , at an elevation of 1,400 m (4,600 ft)
The warm moist air from northern Italy is blocked on the windward side, loses much of its water vapor content, and descends on the French plateau and valley of the Mont-Cenis range in the Maurienne valley .
Rotor cloud revealing overturning and turbulence above the lee slopes of the Antarctic Peninsula during a westerly Foehn event
Foehn clouds upon the Karawanken mountain range, Carinthia , Austria
Foehn clouds over La Palma , Spain