Weak La Niña Could Make For A Wild Winter In CA

CALIFORNIA — La Niña is running late, and she's behaving a bit unpredictably.

A slowly developing La Niña climate pattern is expected to influence how snowy and rainy this winter will play out in California after last year’s El Niño. However, California remains in a neutral weather pattern, and weak La Niña tends to be a less predictable one.

"Forecasters continue to favor La Niña later this year, with an approximately 60% chance it will develop in September–November. The probability of La Niña is a bit lower than last month, though, and it's likely to be a weak event," the National Weather Service announced in the latest climate update.

El Niño and La Niña are opposite phases of the El Niño-Southern Oscillation, a natural climate pattern that causes predictable changes in the tropical Pacific Ocean. They’re not the only factors in weather, but El Niño typically favors warmer, drier weather in northern states and a wetter trend in southern states.

La Niña, meanwhile, is generally associated with wetter, cooler winters in the north, and a warmer, drier season to the south. Both patterns can have an outsized effect during the winter months.

According to the 2024-25 winter outlook released Thursday by the National Oceanic and Atmospheric Administration’s Climate Prediction Center, a few questions remain about how the season will play out in much of the Golden State. The official forecast covers the period of December through February.

On the temperature side, the outlook is tilted in favor of a warmer-than-usual trend for Southern California, while showing even odds for a warmer or cooler winter in the central and northern portions of the state.

While NOAA's prediction favors a drier winter for southern-tier states, California has less clarity. The latest seasonal precipitation outlook shows equal chances for a wetter or drier winter for all but the southernmost parts of California, where the odds are tilted slightly in favor of a drier season.

Plenty of variables can affect how winters develop in La Niña and El Niño years, including the strength of the patterns and the timing of their arrival. A weak La Niña winter was in place during the winter of 2022-23 when more than three dozen atmospheric rivers slammed the West, including many that soaked California.

A recent winter forecast from AccuWeather was bullish on storms developing in California — and for a healthy ski season.

Accuweather predicts atmospheric rivers and storms from the Pacific Ocean will focus on Northern California before tracking over the Rocky Mountains as winter gets underway in December.

This new pattern could open the door for storms to track farther south over Central and Southern California and push inland. January could be the wettest month of the winter for Los Angeles and San Diego, as well as the Inland Empire, AccuWeather said. Another shift in February could focus storms again on Northern California.

Forecasters originally expected a La Niña to develop late last winter, which turned out to be the warmest on record in the continental U.S. and worldwide.

“If it seems like we’ve been stuck here in neutral for longer than we expected — we have!” Emily Becker, an atmospheric scientist at the University of Miami, wrote in the National Oceanic and Atmospheric Administration’s latest La Niña/El Niño blog post.

The climate patterns are predictable, but only in the big picture. Small short-term fluctuations, such as the weaker equatorial trade winds during September, can’t be predicted more than a couple of weeks in advance, at best, Becker wrote.

Forecasters still expect La Niña to develop ahead of the start of meteorological winter on Dec. 1 (the winter solstice on Dec. 21 is generally accepted as the official start of the season). But it is expected to be a weak one.

Strong La Niñas are associated with consistent weather throughout the season, but “a weaker event makes it more likely that other weather and climate phenomena could play the role of spoiler,” Becker wrote.

Overall, NOAA predicts wetter-than-average conditions for the entire northern tier of the continental U.S., particularly in the Pacific Northwest and the Great Lakes region, along with northern and western Alaska. Drier-than-average conditions are expected from the Four Corners region of the Southwest to the Southeast, Gulf Coast and lower mid-Atlantic states.

That could either ease or worsen drought conditions, especially in the central and southern Plains and the Southwest.

“Unfortunately, after a brief period in the spring of 2024 with minimal drought conditions across the country, more than a quarter of the land mass in the continental U.S. is currently in at least a moderate drought,” Brad Pugh, operational drought lead with NOAA’s Climate Prediction Center, said and the statement.

“And the winter precipitation outlook does not bode well for widespread relief,” he said.

Fortunately for California, the seasonal drought outlook shows only limited areas of drought impacting the state.

Patch staffers Beth Dalbey and Bea Karnes contributed to this report.