Foehn wall (ger: Föhnmauer; fr: mur de foehn)
Cloud formation which, during foehn conditions, lies over and along a mountain ridge. The steep leeward boundary of cumuliform clouds that form on the peaks and upper windward side of the mountains appears as a vertical wall. The cloud may extend from the windward side over the peaks and some way down the leeward slopes, where it is evaporating along a line about parallel to the hills. Foehn wall clouds are often known by local names, such as chinook arch or helm.
The foehn wind