In La Ni a years, this buckling tends to occur in certain prescribed locations. The northward bend in the jet stream tends to occur in the easternmost Pacific, and the downstream bend in the western and central parts of North America. The jet stream then turns northeast usually across the Mid-Atlantic States and out into the Atlantic. When this buckling happens in this location, arctic air masses begin to quickly build in northwestern Canada. This frigid air is steered to the south and east by the jet stream winds.
Storms ride the leading edge of that cold air and bring rains ahead and snows behind.
The cold air can come down west of the Rockies at times and bring frigid conditions to the Intermountain region and sometimes even to the Pacific Coast. The cold air usually comes down from the source regions in pieces. Each reinforcement brings more snow and deeper cold. Eventually the 'mother lode' of cold may descend into the states. Even more significant snows may occur in areas bordering this last mountainous high pressure.