Foehn wall

From Glossary of Meteorology

foehn wall

The leeward edge of the orographic stratiform cap cloud as seen from the lee side of a mountain barrier, preceding or during a foehn or chinook event.

The edge is generally abrupt and resembles a wall of cloud ("foehnwand" in German). This cloud often signifies the occurrence of orographic precipitation, especially snowfall in the cold season, over the peaks.
See foehn cloud.