A La Niña winter is just around the corner. Here's what that could mean for the US

CNN
—

Fall is in full swing, but it's not too early to look ahead to winter, especially one that could feel significantly different than the El Niño-dominated last year.

A weak La Niña is expected to develop ahead of the season, affecting temperatures, precipitation and therefore snow across the United States.

La Niña is a natural climate pattern that influences global weather and is characterized by below-average ocean temperatures in the equatorial Pacific. The impact on the weather is most pronounced in the winter months in the northern hemisphere and has a much weaker impact in the summer.

Last winter was the warmest on record for the Lower 48 as it was dominated by El Niño, the counterpart to La Niña, and the world was also warming due to fossil fuel pollution.

The persistent heat prevented many heavy snowfalls in the Northeast and Midwest, creating a winter snow drought, measured in feet of missing snow.

According to the Climate Prediction Center, La Niña is not here yet, but there is a 60% chance of it occurring by November. Once it arrives, it will remain throughout the winter and likely persist until at least spring of next year.

La Niña or El Niño are never the only factors that influence the weather in a particular season or location. However, they are emphasized because they tend to have an outsized impact on winter weather in the U.S. — especially when they are severe.

While it is still unclear how strong La Niña will become, current forecasts suggest weaker sentiment.

According to Emily Becker, an atmospheric scientist at the University of Miami, it depends on the strength of La Niña – the stronger it is, the more “consistent” its impact on the weather can be.

“A weaker event makes it more likely that other weather and climate phenomena could play the role of confounder,” Becker wrote in NOAA’s latest La Niña/El Niño blog.

Previous forecasts from the Climate Prediction Center show many characteristics of typical La Niña winters. That outlook could change when the center releases its latest forecast on Thursday, based on trends toward a weaker La Niña.

No two La Niña winters are the same, but many share common temperature and precipitation trends.

This is due to the behavior of the jet stream—essentially a current of air through which storms travel—which often shifts northward during a La Niña winter. This typically moves stormy weather from the south to parts of the northern United States.

That's almost exactly what the Climate Prediction Center's latest winter forecast shows for December through February.

The entire northern portion of the U.S. is expected to be wetter than normal this winter, particularly the Pacific Northwest, the Midwest and parts of the interior Northeast. Wet weather will be crucial to combat the ongoing dryness and drought in the Midwest.

It's a complete reversal of last winter's pattern, which favored a wetter south and a drier north.

More precipitation than normal does not mean there will be more snow. Temperatures both above and on the surface still need to be cool enough for snow to fall and stick to the ground.

Weak La Niña events tend to produce more snow in the Northeast, while stronger La Niña events produce less snow as warmer temperatures often occur further up the East Coast.

If this year's La Niña turns out to be weak, this outlook could change. Still, the latest winter temperature forecasts from the center aren't ideal for snow lovers in the Northeast.

The season is expected to be warmer than normal across nearly the entire southern half of the U.S. and much of the East. This could mean some winter storms will be wetter rather than snowier in parts of the East. However, with drier and warmer than normal conditions expected in the south, drought conditions could worsen as the season progresses.

Parts of the Midwest, the Plains and the Rocky Mountains could see temperatures closer to normal this winter, while cooler than normal conditions are expected from the Pacific Northwest to parts of the Dakotas.

The combination of wetter and cooler than normal conditions could potentially lead to more snow in the Pacific Northwest, an area where significant snowpack is critical for winter tourism and water supplies in the warmer months.

Northern California is typically wetter during a La Niña winter, but the Climate Prediction Center forecast has the region near normal this season. La Niña was involved in the extremely wet winter that much of the state experienced from December 2022 to February 2023 and during the wet winter before that.

Southern California is expected to be drier and warmer than average – typical of La Niña. It is crucial that the region experiences heavy rainfall over the next few months. Wet weather is needed to end wildfire season. Without enough rain, fires could continue to burn this year due to the oversupply of fire fuels such as grasses and brush.