A small, skier-triggered avalanche on Mt Blackmore on Sunday (Feb 6) would be unlikely to bury a skier or rider, but could push them into or off obstacles. Photo: E Stutzman
On the morning of Sunday February 6, a snowmobiler triggered a slide in new snow on the SW face of Sheep Mountain. The slide triggered remotely while the rider was lower on the slope and he was not caught (the visible track is not from the rider who triggered the slide, his track was buried in the debris field). The crown was about 18" deep and 75 feet wide and the slide and the slide ran about 250 feet.
We skied into Blackmore late yesterday with chief concerns of the weak layer @ around 110cm and wind loaded new slopes. We dug two pits and found no failures in our column or ECTs. With the wind on the ridge we dug a hasty pit near the ridge to see how it was bonding. Again no results.
We decided to ski our lines taking care to avoid potential trigger zones and particularly loaded slopes. About half way down, I took a turn to the skier's left of a spine and the skier's right side had a small surface-level release. This would probably not have buried a skier, but likely would have taken them or a ride above the cliff band.
<p>Snowfall between Friday night to Sunday morning dropped 12-14” of snow in the mountains around Cooke City with up to 0.9” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/null/?cid=nrcseprd1314… water equivalent</a> (SWE). Human-triggered avalanches are likely on slopes where 15-20 mph winds are transporting this snow into unstable slabs. Alex saw evidence of recent natural avalanches on Miller Mountain and explained in his <a href="https://www.youtube.com/watch?v=5Y9gdD8IOwM"><strong>video</strong></a&…; yesterday that the new and drifted snow is sitting on top of a weak layer of facets creating dangerous avalanche conditions. Other skiers in the Cooke City area observed recent <a href="https://mtavalanche.com/node/25763"><strong>natural avalanches on Woody Ridge</strong></a> and just outside the advisory area in <a href="https://mtavalanche.com/node/25760"><strong>Yellowstone National Park</strong></a><strong>. </strong>All of these avalanches are failing on weak layers of snow now buried 18-24” deep (<a href="https://www.mtavalanche.com/images/22/buried-surface-hoar-layer-ynp-nea…;). Avoid wind-loaded slopes where avalanches are likely, and the danger is CONSIDERABLE. Avalanches are possible on non-wind-loaded slopes and the danger is MODERATE. Carefully evaluate the snowpack and avoid areas with terrain traps that would amplify the consequences of an avalanche.</p>
<p>Two nights ago, 4” of snow fell in the Northern Gallatin Range equal to 0.3” SWE adding to the 10” earlier in the week. The wind increased late yesterday afternoon and will continue to transport recent snow into unstable drifts where avalanches large enough to injure or bury climbers, skiers and riders are possible. On Saturday, a group in the Flanders drainage witnessed snow pouring off an ice climb that “probably would have slammed a climber off the route” (<a href="https://www.mtavalanche.com/node/25744"><strong>details</strong></a>). Today, carefully assess the snowpack paying special attention for signs of wind-loading such as blowing snow and shooting cracks in the snowpack. Avoid terrain where features like trees, cliffs and rocks act as terrain traps and smaller avalanches would be dangerous. Human-triggered avalanches are possible today, and danger is MODERATE.</p>
<p>Sadly, a rider triggered a fatal avalanche on Ski Hill in the Lionhead area yesterday. The shallow slide broke across the slope on a steep rollover and the rider was swept into trees and partially buried. Unfortunately, life-saving efforts on-scene were unsuccessful (<a href="https://mtavalanche.com/node/25766"><strong>limited details and photos</strong></a>). Nearby, a different group triggered a small, relatively harmless avalanche that failed 12” deep on buried weak layers (<a href="https://mtavalanche.com/node/25767"><strong>details and photos</strong></a>). In the Southern Gallatin Range a group of skiers got a “whumph” on a small, isolated slope at low elevations, another indicator of weaker snow. Large avalanches in the West Yellowstone area and near Big Sky and in the Bridger Range are unlikely with the above activity being the tragic exception to overall stability. Additionally, these events signify more trouble to come when the wind blows or snow returns.</p>
<p>There is not much soft snow left for transport in the Northern Madison and Bridger Ranges, but windy conditions today may create small drifts adding to those formed this weekend where you could find isolated instabilities especially where they are combined with buried weak-layers 6-18” under the snow surface (<a href="https://www.mtavalanche.com/images/22/northern-bridger-unstable-pit-res…;). Assess the snowpack for localized instabilities prior to entering steep terrain and evaluate the terrain for features that amplify the consequences of small avalanches. The danger is rated LOW.</p>
<p>If you get out, please send us your observations no matter how brief. You can submit them via our <a href="https://www.mtavalanche.com/node/add/snow_observation"><strong>website<…;, email (<a href="mailto:mtavalanche@gmail.com"><strong>mtavalanche@gmail.com</strong></a…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>
Thank you and great work to everyone who participated in this year’s King and Queen of the Ridge event. This year we set a fund-raising record of $29,345! We are greatly appreciative of the support from everyone who hiked, donated, and raised money for The Friends of GNFAC. The King of the ridge this year is Casey Bloomer with 30 hikes, and Queen is Jennifer Allen with 22 hikes!
From Obs: "Today I watched as a sledder dropped a cornice causing the cornice to fall triggering an avalanche chasing him down the hill. The snowpack consisted of a wind slab on top of near-surface facets and a couple buried layers of surface hoar." Photo: B Rasmussen
From obs: "Today I watched as a sledder dropped a cornice causing the cornice to fall triggering an
avalanche chasing him down the hill. The snowpack consisted of a wind slab on top of near-surface
facets and a couple of buried layers of surface hoar."
On Sunday, one snowmobiler in a group of four was caught and killed in a small avalanche on Ski Hill at the south end of Lionhead Ridge. He was on a 45-degree slope when it released and partially buried him against a tree. The slide was only 4"-11" deep, 75 feet wide and ran 300 feet vertical. His head was a foot under the snow. The avalanche was not witnessed and the victim was buried an estimated 15-25 minutes before he was uncovered. Rescue efforts were not successful. The group was familiar with the area and had rescue gear. The shallow, steep slide ended in trees, a terrain trap. Our deepest condolences go out to the family and friends of the rider.
A detailed report can be read here.
Skiers observed several slab avalanches on the east face of Woody Ridge. They broke about 12" deep on a weak layer buried by recent snow. Photo: B Zavora
Skiers observed several slab avalanches on the east face of Woody Ridge. They broke about 12" deep on a weak layer buried by recent snow. Photo: B Zavora
