JACKSON, Wyo. — The Bridger-Teton Avalanche Center (BTAC) shared with Buckrail that even though recently warming temperatures created a period of snowpack instability, the moisture will eventually improve snow stability in the backcountry.
BTAC Director Frank Carus told Buckrail that warming tends to make snow “slabs weaker and more prone to fracturing” in the short-term.
“Wet slab avalanches are probably the hardest thing for forecasters to forecast accurately,” Carus said. “But the one thing that you can say for sure is that warmth and rapidly rising temperatures are just bad in general.”
Carus said that avalanche danger was rated as “high” across all elevations on Monday, Feb. 3, when a group of seven skiers got caught in a wet slide in the North Bowl in the Upper Rock Springs area, outside the boundary of Jackson Hole Mountain Resort. The BTAC reported that while one skier was partially buried, the rest of the group was able to self-rescue with the aid of other ski guides in the area.
“They were out on a high day, in extreme, cliffy terrain,” Carus said. “It was a pretty aggressive choice to make. It’s kind of important for people to realize that you’d better be super careful on high days, and definitely don’t cluster on a big slope on a high day.”
Even though the warmer precipitation created a “widespread avalanche cycle,” Carus explained that this new snow layer will help with snowpack stability in the long-term, especially with cooler temperatures predicted to return.
“Right now, we are over the hump and generally should have improvement in stability,” Carus said. “We are hoping that this warmup will quickly cause this January drought layer to fade and become less of a problem. That’s the good news, that all of the new snow is going to crush the weak layer out of existence, more or less.”
According to Carus, January’s cold temperatures created a thick layer of near surface facets and surface hoar, which he described as weak, sugary snow on the surface. This weak layer was then buried on Jan. 31, when it began to snow in the mountains. Moisture-infused snow increases what Carus calls a “centering process,” which transforms angular snow crystals into rounder crystals that can more easily stick to each other.
On Thursday, Feb. 6, the BTAC forecasted that avalanche conditions in the Tetons are rated as “considerable.”
The BTAC observation reads that since Jan. 31, several feet of snow have fallen on a “weak snow interface, in addition to rain at lower elevations and above-freezing temperatures up to 10,000 feet.” This buried snow layer, if triggered, can move across large distances, according to the report.
“With the nature of the slab of snow above this weak layer, as well as the depth of burial, apparent signs of instability, such as cracking, collapsing or recent natural avalanche activity, are not likely to present themselves before triggering a large avalanche,” the BTAC forecast warns.
Up-to-date avalanche conditions can be seen here.
