The region surrounding the Calgary Edmonton Corridor is notable for having the highest frequency of hail in Canada, which is caused by orographic lifting from the nearby Rocky Mountains, enhancing the updraft / downdraft cycle necessary for the formation of hail.
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In an " unstable " atmosphere, vertical air movements ( such as in orographic lifting, where an air mass is displaced upwards as it is blown by wind up the rising slope of a mountain range ) tend to become larger, resulting in turbulent airflow and convective activity.
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A similar class of winds, the Sirocco, the Bora and Santa Ana winds, are examples where orographic lifting has limited effect since there is limited moisture to remove in the Saharan or other air masses; the Sirocco, Bora and Santa Ana are driven primarily by ( adiabatic ) compression heating.
