Abstract Winter operation of an acoustic sounder at Calgary, Alberta, has led to some unique observations during Chinook periods. Acoustic backscatter records obtained in these periods reveal an identifiable pattern of events in the atmospheric boundary layer. Descending turbulent structures are observed in pre‐Chinook conditions; the arrival of these structures near ground is associated with the onset of ground‐level warming. When ground‐level temperatures have risen to near 0°C, a deep (200–500 m thick) characteristic region of turbulence is generated in the boundary layer. The correlation of these features with surface wind and temperature data is discussed.