DCHP-1 Online
Chinook arch 
a cloud formation that often attends or presages the Chinook winds, observed as an archlike strip of blue sky above the western horizon, often between the peaks of the Rockies and the surrounding overcast.
See also: Chinook sky
- 1941 [Caption] The dark cloud is the "Chinook Arch," forerunner of the warm wind of winter.
- 1964 This Chinook arch appeared in the western sky Sunday but its usual promise of warm air sweeping in from the west is not expected to come true.
- 1941 [Caption] The dark cloud is the "Chinook Arch," forerunner of the warm wind of winter.