There is a decent chance of a La Niña emerging in the fall (September-November) and lasting through the upcoming winter, according to NOAA's Climate Prediction Center.
In fact, NOAA is rather confident about La Niña impacting the first part of winter, saying in a release Thursday there is a 66% chance of the weather phenomenon existing November through January. With that, a La Niña watch has been issued.
This is a more confident outlook than in July 2020 when NOAA issued a La Niña watch with 50-55% confidence. The federal forecasting agency's confidence level in 2020 increased to 60% in an August update, so the odds of a La Niña this year into 2022 are quite a bit higher at this stage.
If the La Niña comes to fruition, the colder Pacific Ocean temperatures and positioning of the jet stream can result in a weather pattern that brings more cold air and sometimes more precipitation to the Northern Plains and Upper Midwest, including Minnesota.
But as the National Weather Service said last year, "every La Niña is different, and not all La Niña winters behave the same way." Also, "the strength of the La Niña may make a difference in how it affects our weather both in terms of precipitation and temperature."
A La Niña winter categorized as "weak" has happened six times since 1950, according to the CPC. Compared to the seasonal snowfall average in the Twin Cities area (54 inches), the snowfall totals during a weak La Niña year have varied, though the most four recent have produced below-normal snowfall.
- 1954-55: 33.9 inches
- 1964-65: 73.7 inches
- 1971-72: 64.4 inches
- 1974-75: 64.2 inches
- 1983-84: 98.6 inches
- 1995-96: 55.5 inches
- 2000-01: 75.8 inches
- 2005-06: 44.4 inches
- 2008-09: 45.0 inches
- 2011-12: 22.3 inches
- 2020-21: 48.7 inches
La Niña is the opposite of El Niño, where eastern Pacific waters are warmer than normal. Here's a explanation from meteorologist Sven Sundgaard:
"This occurs when the trade winds (winds that push east to west along the equator) increase, thus pushing surface ocean water warmed by the strong sun westward where it pools to above normal temperatures near Australia and Papua New Guinea. The result creates upwelling along the South America's coast, which means the deep, cold ocean waters are pushed up to the surface.
"La Nina's effect on Minnesota weather is a bit murky.
"Whereas El Nino is a very strong correlation for milder winters – 3 out of 4 El Nino episodes result in warmer than normal Minnesota temperatures – La Nina almost cuts 50-50 with a slight favorability toward the cooler side.
"There’s also bit more correlation to wetter winter conditions (either more rain or snow).
"One must keep in mind that numerous things impact seasonal weather patterns and La Nina is just one. If other forces are stronger, which our climate models suggest this year, La Nina’s impact may not be much."