Why do tornadoes mainly occur in the prairies in Canada?

Answer 1

Tornadoes are not uncommon on the prairies of Canada because they experience some of the same effects that have led to the high incidence of tornadoes in Tornado Alley to the south. Some even consider the southern portion of these plains to be part of Tornado Alley. In this region it is not uncommon to have collisions of warm, moist air from the Gulf of Mexico, cool air from northern Canada, and dry air from the Rockies. These collisions result in very strong thunderstorms, with the moist air acting as their "fuel." Additionally, the region often has a layer of stable air called a cap that suppresses storms. This behaves like the lid on a pressure cooker, allowing the atmosphere below it to become increasingly unstable until storms develop explosively. Finally, the region often sees strong vertical wind shear, or a variation of wind speed and direction with altitude. This tilts them in such a way that the updraft and downdraft portions becomes separated and don't interfere with one another, letting the already strong storm further strengthen and last longer. The wind shear also sets the storms rotating, turning them into supercells, the most powerful thunderstorms on earth. It is the rotation within these supercells that can develop into a tornado.