Katabatic wind

Katabatic Wind: A local wind produced by the downward motion of cold air off high ground.

This is a katabatic wind (sometimes also called a mountain breeze). If the slopes are covered with ice and snow, the katabatic wind will blow, not only at night, but also during the day, carrying the cold dense air into the warmer valleys.

See also: Direct, Plane, Speed, Section, Wind