The clouds in this arch form at the crest of the Chinook wave. The conditions required for a Chinook are a high pressure system in western British Columbia and a low pressure in the lee of the Rocky Mountains. The strength of the Chinook depends on the moisture content of the air that flows between the high and low pressure systems, the pressure differences between the two systems and the topography of the affected area. As the moist air passes over the mountains it is forced to rise resulting in precipitation on the western side of the mountains. The precipitation dries the air.
Dry air heats up faster than wet air as it descends the eastern side of the Rocky Mountains.
Severe weather events occur in Alberta and can cause significant problems for agriculture. These severe events are produced by unstable atmospheric conditions and include hail storms, heavy rains, wind gusts, high winds and tornadoes. In the case of heavy rain, the risks to agriculture may be located at some distance from the storm itself because heavy rains in the top reaches of a watershed can produce downstream flooding. In general, severe weather events affect a few people greatly at any one time. These conditions cannot be prevented and efforts are currently underway to improve prediction and to provide advance warning permitting safeguards to prevent loss of life and property.