COLUMBUS, Ohio (WCMH) — For the second winter in a row, La Niña will impact weather patterns across North America and around the world, according to the National Oceanic and Atmospheric Administration’s Climate Prediction Center.

La Niña is a cyclical cooling of the eastern tropical Pacific Ocean, which influences the position of the jet stream and storm track. The large pool of cooler-than-average water causes the air to broadly subside over and a northward shift of the upper-level winds in the eastern Pacific.

The winter of 2020-21 was also highlighted by La Niña that formed in the fall and lingered into spring. Last winter was generally milder than normal east of the Rockies, but marked by a very cold and snowy February 2021, with historic winter storms across the Southern states and a deep freeze.

There are many variables that can alter the flow of the jet stream across North America and turn the tables in favor of colder and snowier conditions, chiefly Atlantic pressure patterns and the location of the polar vortex. A blocking pattern in the North Atlantic occasionally develops in mid-winter that allows frigid air to tumble southward across the central and eastern United States, with snow along the northern boundary of low-pressure systems.

Colder air follows the northern branch of the jet stream, with periodic dips east of the Rockies, bringing bouts of wintry weather.

However, the current early-season NOAA projection favors a return to milder-than-normal weather for much of the nation in December.

A variable Pacific jet stream will continue to bring bouts of stormy weather in the Pacific Northwest and northern Rockies, with an active storm track through the Midwest and Ohio Valley.

La Niña is not good news for drought-stricken areas of the Southwest, where drier-than-normal conditions are expected to persist through early winter.