Will El Niño bring a wet or dry winter? For much of the US West, it’s a coin flip

While parts of the Northwest have already weathered their first winter storm this past week, that multi-foot blast of snow was not necessarily a sign of what’s to come this season.

With an El Niño climate pattern already firmly in place, the northern portion of the U.S. will likely be basking in warmer-than-average temperatures this winter, according to a recent U.S. Winter Outlook from the National Oceanic and Atmospheric Administration’s (NOAA).

The greatest odds for these higher temperatures are in Alaska, the Pacific Northwest and northern New England, per the report. At the same time, drier-than-average conditions will likely affect a similar region — particularly the Northern Rockies and High Plains, the report determined.

“They’re more than likely going to have a warmer winter season,” Casey Olson, a climate data analyst for Utah State University’s Utah Climate Center, told The Hill.

In contrast to those northern regions, Olson added that “we would expect to have a wetter-than-normal southwest United States.”

From December through February, wetter-than-average conditions are likely in northern Alaska, portions of the West as well as the southern Plains, Southeast, Gulf Coast and lower mid-Atlantic, according to the NOAA report.

But with this El Niño-influenced trajectory also comes an important wild card: the South-Central Rockies, where the season could either be wet, dry or anywhere in between.

The NOAA analysis predicted near-normal seasonal temperatures for these areas, with the central portion of the U.S. expecting “equal chances for below-, near- or above-average seasonal precipitation.”

“For us, it’s a bit of a coin flip, since we are in between those regions of statistical significance,” Olson said, referring to his own area in Utah and to neighboring Colorado.

During previous El Niño years, the Central Rockies have not endured significant impacts on precipitation levels, added Sam Collentine, chief operating officer and a meteorologist at OpenSnow, a Colorado-based snow forecasting service geared toward skiers.

Usually, however, Colorado does experience a strong start and end to the winter during an El Niño season, according to Collentine.

“What’s kind of perplexing me so far is we’re having a really dry and warm start to the year already in October,” he said.

“I’m waiting patiently to see how the next couple of weeks perform,” Collentine added, stressing that he’d expect to see strong shoulders — the starts and ends of winter —  and a below-average middle of the season.

Regardless of the season’s overall precipitation, Collentine explains that for the winter recreation season in the Central Rockies, the snow supply all “comes down to five, six, seven really strong storm cycles throughout the year.”

“So you could have a below average season — have a couple of good storm cycles during the season — that really leads to good conditions,” he said.

And when adding manmade snow produced by the area’s ski resorts into the equation, most of the region’s slopes can usually open up by Christmas, according to Collentine.

Olson likewise stressed that Utah is “very event driven.”

“We can have a very dry winter for 85 to 90 days, and all of a sudden get slammed with a very strong winter storm that provides a lot of moisture,” he said. “So we’re very reliant on those.”

Snowpack accumulated over the winter not only allows skiers and snowboarders to get out on the slopes but also fuels the flow of the Colorado River as snowmelt in the spring.

As far as water resources are concerned, Olson emphasized this dependence on snowfall and voiced concerns about climate-induced warming that could in the future bring more rainfall instead of snow.

“From a water resource perspective, we’re really interested in a good snow accumulation season as well as a slow melt,” Olson said.

Many Western states have for decades not only been making snow on their ski slopes but have also been engaging in a snow-inducing process called “cloud seeding.”

Cloud seeding, as defined by NOAA, is the introduction of a substance that has a structure similar to ice — such as silver iodide — into clouds, to trigger freezing.

For the process to be successful, the clouds must contain supercooled water, or liquid water that is colder than zero degrees Celsius.

Without sufficient ice nuclei — particles that serve as a hub for ice crystallization — the supercooled droplets may not be converted into ice, according to Binod Pokharel, a research scientist at the Utah Climate Center.

“That is the one reason we artificially inject some of the ice nuclei, that is the silver iodide, which can attract more droplets to convert into the ice,” he said. “And that’s how we can get more snow on the ground.”

During the cloud seeding process — typically powered by ground-based generators — certain conditions must be in place. The cloud must be cold enough, but not too cold, to facilitate ice crystallization, while winds must be strong enough to send the nuclei over the mountains, Pokharel explained.

Utah, Pokharel explained, has been conducting cloud seeding operations for decades and has been receiving continuous funding from the state to deploy this strategy ever since.

While Colorado and Wyoming also engage in this practice, the former only does so at the county level, and the latter only recently launched a program at the state level, Pokharel said.

The states in the Colorado River’s Lower Basin — Arizona, California and Nevada — also supplement Utah’s state funding, as a buildup of snowpack ultimately results in downstream water flow, he added.

In 2023 alone, the Utah State Legislature allocated $12 million in one-time funding, as well as an annual budget of $5 million, to expand the cloud seeding program.

Today, Utah has about 170 cloud seeders and intends to add another 60 manual and 120 remote generators over the next few years, according to the state’s Department of Natural Resources.

In the future, Pokharel said he could see the use of cloud seeding expanding to other parts of the world — perhaps in his home country of Nepal, where the Himalayas have plenty of sources of moisture.

Changing environmental conditions have meant raindrops are now replacing what in the past would have been snow — hampering the ability to store that water for an extended period, according to Pokharel. 

“We have a warmer climate, and we are getting more rain than snow,” he said.