Why is Utah having so many avalanches right now, and when will canyon conditions get safer?

UDOT closes Little Cottonwood Canyon indefinitely as risk of mountains shedding concrete-like slabs increases.

(Rick Egan | The Salt Lake Tribune) Little Cottonwood Canyon is closed due to an avalanche on Thursday, April 6, 2023.

The inordinate amount of snow Utah has received this season — closing in on 900 inches at Alta Ski Area — had been like Botox for the state’s mountain ranges.

The snow has filled in all the ravines, leveled out the areas where trees or rocks might create bumps and erased any other wrinkles and imperfections on the slopes. Basically, it’s smooth sledding for any slab that might break off and careen toward the base.

“We call it grease, but it’s like a really slippery sliding board,” said Mark Staples, the director of the Utah Avalanche Center. “Any snow that comes down, any avalanche that happens, it’s just so much easier for it to come all the way down the road.”

So, that’s what the slabs have been doing, creating chaos, and danger from the East Bench to the top of Mount Baldy. It isn’t just the amount of snow that’s caused the UAC to issue some of its most dire avalanche forecasts on its scale for most of the mountains in Northern Utah, though. The weather has also played its part, and the combination may keep most downhill and backcountry skiers and riders off the slopes, especially in the Cottonwood Canyons, for days or weeks or even longer.

On Monday, the Utah Department of Transportation closed down State Route 210, which leads to Snowbird and the Alta Ski Area through Little Cottonwood Canyon, in both directions for an undetermined amount of time — likely days — because of the threat of avalanches crossing the highway. A UDOT spokesperson estimated at least 30 slides covered the two-lane road between last Sunday and Friday, including one that rushed onto the Chickadee ski trail at Snowbird. They haven’t let up since then. In fact, one crashed through the White Pine area and spilled across the road Monday afternoon while Staples was speaking to the Tribune.

UDOT also has begun restricting traffic on SR 190 up Big Cottonwood Canyon, which serves the Brighton and Solitude resorts, from 11 a.m. to 5 p.m. daily due to avalanche risk. The UAC, meanwhile, has warned of “High” avalanche danger in almost all the mountains between Provo and Logan. The only exception is the Uintas, which has been reduced to “Moderate” after also spending much of the past month at “High.” The UAC’s “High” rating is just one step down from its ultimate and rarely used rating of “Extreme.”

Some of those measures have been taken in reaction to the slides people have already seen in the canyons. Much of it, however, is precautionary. Staples pointed out that few if any avalanche forecasters and UDOT workers have lived through a winter like the one Utah just experienced, and they’re not exactly sure what to expect next from the snowpack.

“We just have a lot of uncertainty,” Staples said “It was just a record-breaking year, [then] it was cold for so long and then all of a sudden spring roared up. These are conditions where, regardless of our forecasts and the dangers — and I hope we’re conveying this in our forecasting — there’s just a lot of uncertainty. All of our forecasters are, personally, giving themselves a wider margin of error.”

One of the main reasons the avalanche danger has been so high for so long in Utah, and is especially picking up now, is the rapid change in the weather.

Staples said that up until a week ago, the threat came from “dry” avalanches. Known for the plumes of snow they send up when they slide, they’re usually triggered when so much snow piles up that the stress exceeds the strength of the snowpack and causes it to buckle. Then, within a matter of days after Utah’s last snowstorm, temperatures soared, reaching the mid-70s in the foothills Monday afternoon and near 80 on Tuesday. That’s creating wet avalanches, Staples said, which he likened to sliding slabs of concrete. Wet avalanches break, he said, when the snowpack weakens and can’t hold the weight already stacked on top of it.

Utah Department of Transportation/contributed This aerial photo shows an avalanche slide in the White Pines area of Little Cottonwood Canyon on Wednesday, April 5, 2023. The highway has been closed since Sunday night due to high and unpredictable avalanche danger and deep snow.

The cooler temperatures predicted for later this week — including the potential for snow again Thursday — should help stabilize the snowpack, Staples said. Cold nighttime temperatures have done just that in the Uintas and in the mountains near Moab. The Moab-area mountains were actually considered at low avalanche risk Monday, but the UAC elevated them to “Moderate” on Tuesday because overnight temperatures didn’t reach freezing.

What the mountains really need, though, is better plumbing.

Staples said if temperatures rise gradually, the melting snow can naturally find a way through the snowpack and drain without causing further slides. Ideally, he said, the mountains will experience a late spring hard freeze, which would harden those runoff channels and basically turn them into rebar for the snowpack. Don’t, however, expect that to happen overnight.

“That could take a while,” Staples cautioned, “because we have very deep snow.”

That could be disheartening news for skiers wanting to get in a few more runs before Alta is scheduled to close for the season on April 23 or for backcountry travelers wanting to take advantage of the rare abundance of snow and sun. It’s even an issue for hikers and snowshoers at lower elevations who Staples advised should also assess their routes for avalanche risk and be on alert.

Chris Adams, president of the Wasatch Backcountry Alliance, a ski and splitboard touring advocacy group, said he is still going backcountry skiing several times a week. With the risks in mind, he picks his spots carefully and his group advises its members to do the same.

When it comes to closing the canyon roads, Adams said, “I don’t love it, but I get it.

“We keep hearing, like, exceptional, unprecedented, all these words thrown around. But it’s true. It really is. We’ve broken as far as I can tell, like all the [snow] records, right? So we share those messages from UDOT and we certainly want to make sure that our membership is informed and aware and respectful and not causing problems.”

Adams said he suspected many of WBA’s members spent the warm weekend biking, gardening and golfing instead of skiing. Staples said they had the right idea.

“Let the snowpack go through this transitional phase,” he said. “It’s uncertain how long it’ll take, but you’re going to have a hard time finding really great snow conditions right now.”