The chinook winds are a unique phenomenon along the eastern slopes of the Rocky Mountains. They are usually accompanied by a band of clear sky extending in a linear pattern with a defined cloud edge adjacent.

It can provide some breathtaking and dramatic lighting, clouds and colours.

For more information see

http://www.cdli.ca/CITE/chinook.pdf

http://en.wikipedia.org/wiki/Chinook_wind

or an colourful photo by Pbase artist Gary Hebert

http://www.pbase.com/image/33980504