Endless Snow and Volatile Weather Shape Utah Avalanches in 2022/23

This winter was one for the record books. The 2022/23 season was by many measures historic, with Alta recording nearly 900” of snow and Utah registering its wettest winter in recorded history. But along with bountiful snowfall, the winter presented periods of significant, and at times unprecedented, avalanche activity, which snarled canyon traffic, challenged ski resort operations and tragically killed three people. The enormity of snowfall at times overwhelmed the snowpack’s and our own ability to cope.

Natural avalanche cycles led to repeated periods of interlodge at resorts like Alta and Snowbird, while periods of massive snowfall and rapid warming forced road closures in Little Cottonwood that lasted for days at a time and on U.S. 189 in Provo. Perhaps never before have Utah Department of Transportation (UDOT) and ski resort personnel been tasked with such an arduous and Sisyphean ordeal to mitigate avalanche danger.

utah avalanches

The primary cause of avalanche activity this season is not difficult to understand. Continual heavy snowfall repeatedly overloaded slopes to the point that avalanches released. It’s not unusual for this to happen in Utah. Copious snowfall is the Beehive State’s calling card after all. UDOT staff and resort ski patrols are well prepared for this, and both utilize explosives to release avalanches during and after storms when members of the public won’t be impacted.

This season’s storms came so frequently with such ferocity it was simply difficult to keep pace. Further complicating matters, avalanche paths in the Utah mountains this season became greased—meaning they were filled in with deep snow and cleared out by previous avalanches—which caused avalanches to run farther than is typical.

A more thorough look at the 2022/23 avalanche season reveals a unique snowpack behavior in comparison to prior years. The notably dangerous 2020/21 season was marked by persistent slab avalanches. In very simplified terms, periods of dry, clear weather led to the formation of weak, faceted grains—think sugary, crystallized snow that doesn’t pack well into a snowball. When those grains were buried by subsequent snowfall, they became long-lasting instabilities upon which avalanches would slide when overloaded by new snow or impacted by skiers, snowboarders or snowmobilers.

This season’s avalanches, at least after New Year’s Day—were primarily caused by instabilities within the new snow. A deeper snowpack tends to be more stable than a shallower snowpack, owing to some basic principles of temperature, pressure and the rate at which water vapor moves through the snowpack. Utah’s snowpack was certainly very deep with properties that would trend towards stability this season, but snow adapts well to gradual change, rather than rapid change. With storms lining up back-to-back off the pacific depositing feet of snowfall at a time, the snowpack rarely had time to adapt to new loads.

Just as snow adapts well to gradually added loads, it adapts to gradual temperature changes. Rapid temperature increases release water into the snowpack, in between individual snow grains and occasionally deeper in the snowpack causing wet avalanches. When spring suddenly arrived in April on the heels of yet another massive winter storm, the snow didn’t have time to adapt and wasn’t able to solidly refreeze overnight. The resultant apocalyptic wet avalanche cycle led to a closure of Little Cottonwood Canyon for the better part of a week as wet avalanches on well-greased paths overran the S.R. 210 time and time again.

No season or snowpack can be defined by a singular characteristic. Terrain, sun, precipitation and wind all combine to create a degree of spatial variability that will always confound, but the 2022/23 season will forever be remembered for monumental snowfall and the remarkable depth of the resultant snowpack. The season’s avalanche activity was marked by the same properties, with seemingly endless snowfall and volatile weather creating hazards different that most are accustomed to. Between the bottomless powder days and the awe-inspiring avalanche cycles, this season has been one we’ll never forget.  

Tony Gill
Tony Gillhttps://www.saltlakemagazine.com/
Tony Gill is the outdoor and Park City editor for Salt Lake Magazine and previously toiled as editor-in-chief of Telemark Skier Magazine. Most of his time ignoring emails is spent aboard an under-geared single-speed on the trails above his home.

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