The Coming Storm
Scout Edmondson
At the end of the 2023 winter, the San Juan Mountains, just north of Durango saw a record-breaking snowpack.
According to the National Resource Conservation Service, a branch of the US Department of Agriculture that tracks historical snowpack data, the snowpack in The San Juans topped out at 31.5 inches of snow-water equivalent (SWE) in mid-April. Purgatory Ski Resort, located a half-hour north of town, received 376 inches of snow last season, topping their previous record by over 100 inches.
To put it plainly, a lot of snow fell last winter.
The San Juans are at the headwaters of the San Juan, San Miguel, Dolores, and Animas rivers. The last time they saw that much snow was in 1993, which still holds the record for the deepest snowpack in the past 30 years.
But last winter was a La Niña year. And what was strange, according to Andy Gleason, Senior Lecturer of Geosciences at Fort Lewis College, was that we shouldn't have gotten that much snow.
“When you look at the statistics of how much snow we get during a La Niña year versus an El Niño year, we typically get less snow during the La Niña and more during the El Niño,” Gleason said. “But we typically don't get these large atmospheric rivers during La Niña years. It’s an anomaly for us.”
2022/23 was a La Niña year, meaning that temperatures over the ocean were warmer around equator and cooler around the North Pole. That difference in temperatures created an area of high atmospheric pressure around the Equator, which pushes any moisture that evaporates off the Pacific Ocean to north. From there, the jet stream—a fast-flowing current of wind located 30,000 feet above the Earth’s surface that moves from west to east—moves that moisture inland, causing more snow and rain to fall over places like Washington or Canada, Gleason said.
However, warming atmospheric and oceanic temperatures have led to more water evaporating off the ocean. All that water vapor in the atmosphere then moved in over the Southwestern United States like a giant river in the sky, causing unprecedented amounts of snow and rain to fall—like we saw last winter.
“These atmospheric rivers definitely brought more moisture,” Gleason said. “Typically during a La Niña event, the jetstream is shunted towards the Northwest. The Pacific Northwest gets a whole lot more moisture, and then we get what's leftover.”
Gleason said that since more moisture is pushed to the north in a La Niña year, Northern Colorado usually gets more snow. Most of the atmospheric river events that occurred last winter came off the Pacific from the South, which is why places like California and Durango saw so much more snow in 2023.
Jeff Weber, the Scientific Project Manager at the National Center for Atmospheric Research, said that 2023 was the third La Niña year we saw in a row.
However, the Earth’s atmosphere started to shift towards an El Niño towards the end of the 2023 winter, he said. This shift played into why there was so much moisture being delivered to the Southwest. Weber said that by this winter, the El Niño will be in full swing.
For Weber—an avid skier—2023 was a welcome year after several lackluster winters.
“This low pressure trough also led to persistent low temps, which allowed the snow to hang around and make it really feel like winter, finally,” Weber said. “I love the cold and snow, and it has been missing of late.”
That much snow was definitely great for skiers and snowboarders, but it was also especially good news for a drought-stricken West. The severity of drought throughout the United States fell significantly in the ‘22/‘23 winter, according to the National Centers for Environmental Information.
Sara Burch, FLC alumna and The Animas Riverkeeper at the San Juan Citizens Alliance, said that much snow was helpful for state governments to start refilling reservoirs like Lake Powell or Lake Mead. Those reservoirs, among others throughout the southwest, reached historic lows in 2022 and raised concerns among state governments about delivering water and hydroelectric power to cities like Las Vegas and Los Angeles. Weber and Gleason agreed.
“The inflow for each reservoir is predicted to be more than it has been for the past few years, but it doesn't mean that we're out of a water crisis,” Burch said. “It might just give a buffer for those that are in extreme water shortage. I think this time is more critical than ever for water managers to put in long term plans for water infrastructure.”
Weber is hopeful that this winter will bring a healthy amount of precipitation as the atmosphere shifts from a La Niña to an El Niño, which could continue to help ease drought conditions.
FLC Alumnus Zach Bane stands in an eight-foot-deep snow pit while out skiing in the San Juans last winter.
“The Southwest U.S. has been in a drought for over 20 years now, we will need another 20 of non-drought to catch up,” Weber said. “Last winter was a great start, and now an El Niño is looming, so hopefully that plays out very wet.”
Weber also said that reservoirs will have an increasingly important role in the coming years when it comes to storing water that people can use.
Climate scientists like Weber predict that climate change will boost the amount of water evaporating off the Pacific Ocean, but that water will likely fall as rain instead of snow.
“Overall, the precipitation amount in total could actually increase, as a warmer atmosphere can carry more water vapor,” Weber said. “But there will be less free storage as snow.”
Gleason said that learning how to better understand climate change’s effects on snowmelt is important to the people who manage these reservoirs.
“I've been looking at climate models on snow since about 2001, and what they've predicted is that we'll get about the same total amount of SWE, but it'll come on later in the season and melt off earlier in the spring,” Gleason said. “That has a significant effect on people who use SWE, like reservoir managers, who need to know what level to lower their reservoir to in the spring, based on the amount of water in the snowpack.”