The February 7 Pre-Covid Utah Super Cycle
Wednesday Feb 5, 2020 I was surprised to learn my group of eager father and son ski touring guests had shrunk by one. One dad got a flight out of Salt Lake International early that morning, because of concern he might get stranded in Alta. A sizable storm was forecast for the coming days. Little did I realize his foresight would prove to be laser-sharp!
That day we skinned up into White Pine Canyon without him, after shuttling down from the Goldminer’s Daughter Lodge (GMD). Snow was light and “blower.” Temps were cold, and “cold smoke” was the descriptive term for the layer of stellar dendrites that piled up quickly and floated around the boys like a bubble bath as they shredded it. Smiles were ubiquitous among the sons, dads, Billy Haas and me. We all love Utah’s finest champagne.
But, this layer was destined to be the catalyst for a historic avalanche cycle in upper Little Cottonwood Canyon. And when no one gets hurt, and LCC inhabitants get to watch some towering plumes of avalanche debris billowing out of the gulches, those of us who love to see, and/or safely trigger avalanches, got treated to another awesome aspect of life in LCC.
My ski guests and I toasted the sweet backcountry powder day with cold beer in the “polar bear lounge,” aka GMD parking lot, as a few last flakes swirled around us. The super-psyched guests gave back their beacons, and went into the lodge, as a much different storm worked its way into the Wasatch Mountains. They would remain there for the next 50+ hours. The bar became a popular place with stir-crazy guests. Beer kegs ran dry.
I tried to head back up the canyon the following morning, to no avail. The Sheriff turned us back at the base, no questions or exceptions considered. “The canyon’s not opening today,” the officer said, flatly. “No reason to sit here and wait!” Indeed, it would’ve been a LONG wait.
Returning my office it seemed like an overreaction to shut down LCC for the day. Resorts also never opened. Yet the temps were mild, there was little precipitation in Salt Lake City, and the mountain snow totals weren’t impressive. I called Mike Morris, a patroller at Alta. “What’s going on up there?” I asked. “Was it an active morning on avalanche control routes?” “Not really,” he replied. “The dense new snow wasn’t super-reactive. But the moguls are all covered and its great graupel skiing. We’re riding on top of it, like butter. And UDOT did have a slide cross the road.”
This report of only minor avalanching strengthened my impression that the normally savvy avalanche hunters in LCC were being a bit paranoid this time. Better safe than sorry though, I thought, and focused my attention on guide service ramifications. Guests stuck in LCC had to be refunded, since backcountry skiing there was a no go, and avalanche classes for the weekend would have to go somewhere else for field sessions. The Alta Library indoor lecture venue had to be replaced as well.
This warm, wet storm came in on a southwest flow, and immediately started adding weight to the light, fluffy layer beneath it. Then, as winds switched to the northwest, the cards were stacked just right for collapse. It was the “Perfect Storm,” as Utah Department of Transportation (UDOT) forecaster, Brett Korpela put it, “…to produce a 40-year avalanche cycle in LCC. We had 27 avalanches cross the road during this storm cycle.”
It’s essential to understand that SWE (snow water equivalent) is far more important in making slides than snow totals. This storm/avalanche cycle was a perfect example. Mr. Korpela used forecaster lingo to lay out the facts. “This storm was a big one with 104 cm (41inches) of snow @ 173 mm (6.8 inches) of water.” A typical Alta storm bringing 41 inches of powder would equate to 2-3 inches of SWE. So this one added weight to the slab remarkably fast. And it fell on stellar dendrites, aka “Alta powder flakes.”
To make matters worse (or better depending on your perspective,) as avalanche hunters well-know, wind transports snow (and SWE) far faster than it can fall from the sky. Korpela pointed out, “The real clincher was the sustained 11,000 ft. winds out of the northwest, and above at 30 mph for 60 hrs. We had an upside down setup that was easily overcome by the water amounts and wind loading coupled with graupel pooling that seemed to reinvigorate the energy of the avalanches once they reached a lower elevation.”
Dense graupel, (aka “popcorn snow,”) is common in relatively warm storms, like this one. It falls in tiny pellets that roll down off the steepest terrain and pool at the transitions to lower slope-angles. Skiers ride on top of it, rather than getting “pitted” in light powder. As the planet warms, we see more graupel in LCC than in the “good old days.” Are monstrous avalanche cycles like this one, and others in recent southwest flow seasons, going to become the new normal? Yet another upshot of global warming? Should we invest in snow sheds?
The biggest slide of the cycle came off the Southeast Face of Sunrise Peak and barreled down Tanners Gulch, creating, as Korpela noted, “…three distinct deposition areas in the runout.” Tanners features a long, low-angle, glacier-carved gorge at the bottom that slows down avalanches. Even the size 4.5 avalanche (D5 is the largest a slide path historically ever goes) that ripped out at 3:20 am on February 7, didn’t make it to the highway, although it tried hard and did some forest damage as it bulldozed a deep trough toward the road!
LCC highway makes a big curve away from the canyon’s north wall to go around the long, flat, wooded (by disaster species) alluvium deposited by the ancient glacier. This intelligent routing prevents even such huge avalanches rumbling out of Tanners from reaching the road. We’ve seen debris piles 50’ high in past years. Perhaps the debris near the highway was shorter in stature this time because of the graupel pooling and multiple deposition zones upstream. One such deposit at the highest transition zone, was still 30’ deep in mid-June, despite a record-warm and dry spring! I took advantage of the unusual late season snow cover to teach snow school en-route to the summit of Sunrise. And I got inspired to pen this piece.
Up-canyon from Tanners, Highway 210 hugs the north side of the canyon, crossing directly beneath the White Pine Finger Chutes, where there is essentially no low-angle runout. This is why more slides paste the road here than anywhere else. But these are shorter, more confined paths, and didn’t create big debris piles on Feb. 7, 2020. They never do. Avalanche sheds would be short, cheap and effective here. No other road in the world is as busy and avalanche-prone as this one, and lacks sheds in such locations.
White Pine proper is the next major slide path going up-canyon. It features an outdated avalanche berm of granite blocks, aka the ‘China Wall’ that stops medium-sized avalanches. On Friday, Feb 7, according to UDOT, “White Pine ran naturally at around 0458 as well and covered the road 20 ft deep. We had a confirmed infrasonic alert from this slide. D4.”
Bill Nalli, a previous LCC forecaster, explained to me after a series of road-smacking avalanche cycles in 2017, “China Wall acts more like a jump than an effective avalanche berm.” The 20’ tall berm with a small trough behind it is easily overrun by class 4 avalanches. It could be tripled in size, and/or another shed could be installed. The latter would need to be MUCH longer than in “The Fingers.”
Up-canyon from White Pine to the South Ridge of Superior is the zone that saw the most significant forest destruction I’ve observed since I arrived ’85. A sizable aspen grove, and many conifers were strewn across the road. “A little before the Tanners avalanche came out,” Korpela recalls, “the Cottonwood Ridge avalanche path (runs out of the Monte Cristo drainage) ‘naturalled’ and covered the road and Snowbird Entry One all the way into the creek bed. D4.”
Natural avalanches don’t require any human coaxing. No explosives. Not even a ski cut. The rate of loading simply overcomes the bonds at the weak layer interface, and the slab releases. Fortunately, this occurred in the wee hours of the morning, while the road was (deliberately) closed. Obviously, the forecasters saw it coming as they watched the wind speeds ramp up and stay strong, even as snowfall continued. They also planned ahead by sending most of the recreational public down the canyon the prior evening.
As they predicted, the “precipitation index” in the starting zones was being dramatically enhanced by wind loading along the ridges. Northwest winds, with fresh snow available for transport, soon overloaded the upside-down snowpack. This was a basic avalanche 101 formula for slides to run. And they came out en masse. The debris piles below Snowbird were wide and woody. Hundreds of trees met their demise as the powerful white waves mowed them down.
Slides came off Superior, leaving some long fracture lines visible from the road. But these were standard-size repeaters, and no major vegetation was damaged.
Cars were hit in the Alta’s GMD Lot, near the Peruvian Lodge, which was also slightly impacted, as usual by the Toledo Peak Path. A cabin near the bypass road below Alta sustained damage from a slide off East Hellgate. Fortunately, Hugh Ferguson, a great builder, owns it. Replacing windows and cutting up firewood gave him some unexpected, low-paying summer work.
All skepticism about UDOT’s handling of the cycle was erased when the road finally opened, and motorists saw the mangled masses of trees, snapped like twigs, bent like bamboo, tangled and imbedded at all angles in the dense debris piles, that seemingly ran continuously from White Pine to the ‘Bird. In addition to the huge naturals, avalanche front-line workers shot many slides down, with plenty of assistance from Alta and Snowbird Patrollers. And the 24/7 plowing effort was highly commendable.
In summing it up, Korpela said, “We had a lot of cooperation between all the entities that work in the canyon, including the ski resorts, UPD (Unified Police Department) and the Alta Marshalls office. Their help, coupled with good timing and a window where we were able to evacuate most of the recreational public out of the canyon the evening of the 6th, set us up for success.”
Most lodge guests didn’t want to get out of the canyon at this time. They were holding out to have the ski resort to themselves after the storm. They were not so lucky. Crews had heaps of cleanup to do on the only road in and out of Alta before it could re-open, even for just one lane. Chainsaws were as important as snowplows.
After the “shit hit the fan” on Feb. 7, those incarcerated in LCC set a new record for continuous hours of being stuck inside, wishing they could ski. Interlodge travel restrictions remained in effect for 54 straight hours! Although many guests ended up going home without skiing, it was an experience they’d never forget. A quarantine they’d much prefer to the one that ended up defining 2020…A risk they’ll gladly take again for the possibility of powder.
When things finally settled out, we skied the West Slabs of Mt Olympus. The wet snow had plastered itself to the 60-degree rock climbing face. Many other steep lines in the incredible shrinking Wasatch also saw tracks. High pressure set in, and it snowed little for the next month.
When it started snowing again in mid-March, Covid-19 came to America. Ski resorts shut down, and everyone went touring. Then people started fighting about whether or not to wear masks!? Avalanches became distant memories. The least of our worries. But I’d rather remember 2020 for that epic avalanche event than the divisive pandemic. Leaders in LCC handled their challenge much better. Nobody died, economic impacts were short-term, and we were back skiing again in just a few days.