It may be August, but early indicators are already brewing for what the 2023-24 winter season could look like in Colorado.
At Breckenridge Ski Resort, a dusting of white on Peak 6 was photographed on August 11. Whether it will herald another blockbuster ski season remains to be seen, though one factor is nearly certain: atmospheric patterns are set to change this winter.
“We are going into what looks to be a strong El Niño season,” National Weather Service meteorologist Bernie Meier said.
El Niño patterns can form when surface temperatures in the equatorial Pacific Ocean (off the coast of South America) rise above average by 0.9 degrees Fahrenheit for three consecutive months, according to Meier.
El Niño pushes the jet stream south and can bring more precipitation and cooler temperatures to southern regions. In Colorado, this can translate to heavier, wetter snow in the southwest, particularly for the San Juan Mountains, as well as the central mountains. In the state’s northern areas, such as Steamboat Springs, weather may be warmer while snow is dryer, Meier said.
“Not every year is a great snow producer, but if you look at the history, we tend to do better than not for snowfall with El Niño,” Meier said of the southern and central mountain region.
A July projection from the National Oceanic and Atmospheric Administration shows a greater than 90% chance of an El Niño pattern persisting through the December 2023 and February 2024 winter season across the United States.
The prediction comes after the past three winters saw a La Niña pattern (the inverse of El Niño), according to an August 14 report by meteorologist Alan Smith on OpenSnow.
La Niña occurs when the same ocean temperatures fall below average and is defined by wet, cold weather in the north and dryer, warmer weather in the south. According to Smith, the succession of La Niña patterns over the past three years has only happened three times since 1950 — a “rare occurrence.”
“Confidence is increasing that we could see a strong El Niño this year,” Smith wrote in his report, adding the last strong El Niño pattern was in 2015-16.
However, neither pattern guarantees an outcome for winter conditions, especially at the local level.
“It’s one of the few things that we have any shred of ability to forecast six months in advance,” said OpenSnow founder Joel Gratz. “Just because there’s a correlation, it doesn’t mean that every year is guaranteed to be that way.”
Last winter’s La Niña pattern should have been characterized by heavy snowfall in the north and less in the south, but that wasn’t completely the case in Colorado.
While snowfall continuously blanketed the state’s northwest, making 2022-23 the second snowiest season on record for Steamboat Resort, storms also favored southern mountains, with Purgatory Resort reporting one of its best snow seasons on record.
Even the central mountains, which are typically forecasted to see less snow under La Niña conditions, received above-average snowfall and several surprise powder days.
“It kind of broke the rule of what you’d expect last year,” Meier said of the La Niña pattern.
By late last winter, however, the La Niña pattern had begun to phase out, with ocean temperatures beginning to rise in March, Meier said.
“We’ve almost met the conditions for El Niño already and should carry on into winter and next spring,” he added.
Though a stronger La Niña or El Niño pattern can mean average or above-average snowfall, in some areas there isn’t a strong correlation between snow and atmospheric patterns, such as around Colorado’s Continental Divide.
And a 90-day forecast from NOAA shows equal chances for above, below or normal temperature and precipitation, making it anyone’s guess for how the beginning of ski season will kick-off in the Colorado High Country.
“I’m curious to see how this is going to play out,” Meier said.
