If you were hoping for an especially snowy winter, you are likely to be disappointed. The latest winter weather outlook calls for below-average precipitation in southern Utah and much of the Colorado Plateau.
The National Oceanic and Atmospheric Administration forecast for December through February also predicts nearly all of Utah will see above-average winter temperatures.
Matthew Rosencrans, a meteorologist with NOAA’s Climate Prediction Center, said it’s a sign of how the developing La Niña weather pattern is expected to impact the region.
“It's not 100% that La Niña gives you dry, but it's just another thing on that side of the room saying ‘dry,’” he said. “As you go across the Four Corners region, you start to see that signal get stronger.”
A drier-than-normal winter would be in line with how La Niña has historically impacted the Southwest, and it could spell trouble for Utah’s drought and snowpack going into 2025.
La Niña is the cool phase of a cycle known as the El Niño-Southern Oscillation, when temperatures in the Pacific Ocean drop below normal. But it isn’t the only weather pattern influencing Utah’s winter.
A longer-phased oceanic cycle called the Pacific Decadal Oscillation is in its negative phase, which also typically means drier conditions for the West. In some years, these two weather patterns can cancel each other out, Rosencrans said. But in this case, both trends are combining and point toward less precipitation for the region.
“The long-term trends are saying dry. The La Niña’s saying dry for southern Utah,” he said. “You can have week-to-week periods [of wet], it’s just we're hearing more ‘dry’ from the tools this year.”
That doesn’t mean there won’t be storms, he said, just that Utah would be less likely to see as many as it usually does.
Above-average winter temperatures wouldn’t rule out snow for Utah this winter, but it could push it up into higher elevations. La Niña typically brings above-average moisture to the Pacific Northwest. Rosencrans said the western slopes of some northern Utah mountains can occasionally piggyback on that and end up with extra snow, too.
With a 57% chance of La Niña starting by the new year, there’s still a fair bit of uncertainty. NOAA’s forecast does feel stronger — a 74% chance — of La Niña kicking in before the end of January.
If it does develop, this particular La Niña would arrive later than expected and later than it typically does, said Emily Becker, associate director of the University of Miami Cooperative Institute for Marine and Atmospheric Studies.
In 75 years of historical records monitoring La Niña, she said there have been only two other times when it developed this late in the calendar year. Since La Niña’s impacts tend to peak during the winter, the late start would allow less time for it to strengthen and therefore points to a relatively weak La Niña this time around.
Even if ocean temperatures don’t quite hit the official La Niña benchmarks, the southern U.S. could still see drier-than-normal weather.
“It's not like if La Niña suddenly crosses this threshold, we will suddenly have an onset of La Niña conditions,” Becker, who also writes for NOAA’s blog about El Niño and La Niña, said.
“It's not like a switch gets flipped.”
Another factor increasing the uncertainty around La Niña’s arrival is global warming. Climate change is fueling record-warm ocean temperatures, and scientists are still figuring out what that means for measurements based on historic patterns.
“It makes the predictable things a little less predictable,” she said, “because we're not entirely sure how La Niña itself and then its downstream impacts will operate in this warmer world.”
It’s possible that Pacific Ocean temperatures might be too warm to fit the La Niña definition but cool enough relative to the rest of the world’s oceans that they still trigger the pattern’s typical atmospheric effects.
Utah’s soil moisture levels are already below average as of November, and 20% of the state is in moderate or severe drought. Dry soil absorbs moisture before it can reach streams and reservoirs. Since 95% of Utah’s water supply comes from snowpack, a dry winter could threaten to wipe out the gains from the past two wet winters.
If the forecasts hold, reduced snowmelt in the spring might also be bad news for the already-strained river system that the Southwest depends on.
“You'll get lower flows in the Colorado River. You'll get the higher need for irrigation,” Rosencrans said.
“There's going to be increased water demand relative to that supply.”
