Multiple Loose Snow and Storm Slab Avalanches at Lionhead
Riding below Lionhead Ridge on 1/2, we observed several relatively small slab avalanches that failed below the weekend's snow. As well as several loose snow avalanches in steep terrain.
Riding below Lionhead Ridge on 1/2, we observed several relatively small slab avalanches that failed below the weekend's snow. As well as several loose snow avalanches in steep terrain.
At about 10 AM I was belaying my partner on the first pitch of Bobo Like in the Flanders drainage of Hyalite Canyon. We heard a low rumble and a couple seconds later we were engulfed in snow that poured out of the the pitch 2 gully, and seemed to keep coming for about 5 seconds. My partner, who was on lead, was lucky enough to be at the base of the vertical ice of p1, so the snow mostly went over his head. I was off to the side and close to rock at the base and was engulfed in loose snow, but not buried or injured. We continued up afterwards. When I was at the top of the second pitch, belaying my partner up, another small loose snow avalanche came down as river of snow, passing me as I hugged the anchor, and washed over my partner while he was on the pitch. We were fortunate to have both been in positions to handle these avalanches without incident or injury. In retrospect, the clear day and blasting morning sun likely loosened the snow above the gully and funneled it all down onto us. After the first avalanche, the sun must have kept moving onto new slopes above, releasing more snow. Even with a moderate danger level in the avalanche report for the day, with natural avalanches unlikely, we happened to find ourselves in a very specific scenario, with morning sun and a dangerous terrain feature, that still put us at risk. Hopefully we will use this experience to improve our assessment of risk, terrain, and evolving conditions in the future.
On Jan 2, a natural avalanche released in the gully above Bobo Like in the Flanders Drainage and washed over a pair of climbers. No one was caught or injured.
Great riding and beautiful views all day. We did not observe any avalanche activity, but we did not cover much of the range's western portion. We did get some long views from the top of Sawtelle.
In our snowpits, the structure generally looked similar to what we have seen in the Lionhead area. There is a 2-3” thick layer of facets buried 18-24” deep and a layer of facets near the bottom of the snowpack. In the deeper of our two pit locations, these layers are 1F hardness and I guess they are strengthening. However, we did have propagating results in both pits on the layer buried 18-24” deep (ECTP26 and ECTP28) and near the bottom of the snowpack in our shallower pit above East Hotel Creek (ECTP20). Human-triggered avalanches are possible on either of these layers, but we didn’t see evidence (avalanches) that they are hair-trigger or a widespread issue at the moment. Conditions will become dangerous during the next loading event.
At about 10 AM I was belaying my partner on the first pitch of Bobo Like in the Flanders drainage of Hyalite Canyon. We heard a low rumble and a couple seconds later we were engulfed in snow that poured out of the the pitch 2 gully, and seemed to keep coming for about 5 seconds. My partner, who was on lead, was lucky enough to be at the base of the vertical ice of p1, so the snow mostly went over his head. I was off to the side and close to rock at the base and was engulfed in loose snow, but not buried or injured. We continued up afterwards. When I was at the top of the second pitch, belaying my partner up, another small loose snow avalanche came down as river of snow, passing me as I hugged the anchor, and washed over my partner while he was on the pitch. We were fortunate to have both been in positions to handle these avalanches without incident or injury. In retrospect, the clear day and blasting morning sun likely loosened the snow above the gully and funneled it all down onto us. After the first avalanche, the sun must have kept moving onto new slopes above, releasing more snow. Even with a moderate danger level in the avalanche report for the day, with natural avalanches unlikely, we happened to find ourselves in a very specific scenario, with morning sun and a dangerous terrain feature, that still put us at risk. Hopefully we will use this experience to improve our assessment of risk, terrain, and evolving conditions in the future.
<p>Persistent weak layers buried in the snowpack from Cooke City to the Bridger Range to West Yellowstone make avalanches failing deep within this winter’s snowpack possible. These could break 1-2 feet deep on a layer of weak near-surface facets or 3-6 feet deep on sugary snow near the ground. Since December 31st, avalanches broke on weak layers under the weight of riders on Sheep Mountain near Cooke City (<a href="https://www.youtube.com/watch?v=Tsr8x3PCG3s"><strong><span>video and d</span></strong></a><a href="https://www.mtavalanche.com/node/27426"><strong><span>etails</span></st…;), at Lionhead near West Yellowstone (<a href="https://www.mtavalanche.com/node/27430"><strong><span>video and details</span></strong></a>), in the Taylor Fork (<a href="https://www.mtavalanche.com/node/27474"><strong><span>details and photos</span></strong></a>), and naturally in Cabin Creek (<a href="https://www.mtavalanche.com/node/27490"><strong><span>details and photos</span></strong></a>). Sadly, on December 31st, a rider triggered a fatal avalanche on Crown Butte (<a href="https://www.mtavalanche.com/node/27422"><strong><span>video and details</span></strong></a>). The same weak layers exist in the mountains around Bozeman and Big Sky. Standing in a pit in the middle of a large avalanche path on Saddle Peak yesterday, Doug was “Not stoked” and pulled the plug on his descent (<a href="https://www.youtube.com/watch?v=8T2VFhPHOV4"><strong><span>video</span>…;
<p><span>The challenge of <em>moderate danger</em> is that some slopes will slide under the weight of a skier or rider, but the probability of instability is lower on many others. Assess slope scale stability<em> </em>before considering travel in avalanche terrain. Yesterday, on Mt. Ellis, we did our homework and decided the likelihood of instability on that slope was low before deciding to travel in avalanche terrain (<a href="https://www.youtube.com/watch?v=2KNZ5czf_U0"><strong><span>video</span>…;). The day before on Little Ellis, a group dug and found less stable snow and decided to keep things mellow (<a href="https://www.mtavalanche.com/node/27483"><strong><span>observation</span…;). This is how it works. </span></p>
<p>For the future, we are seeing (and many are reporting) a layer of beautiful, feathery surface hoar growing on top of the snow in all corners of the advisory area, including Buck Ridge, where Ian rode yesterday (<a href="https://www.youtube.com/watch?v=wCXEJtfHRtI"><strong><span>video</span>…;). If new snow buries this layer before the wind and sun destroy it. It will become a new weak layer. An inch of fresh snow near West Yellowstone may have done this yesterday. Stay tuned. <span> </span></p>
<p><span><span><span>Carry and practice with a beacon, shovel, and probe. Dig and test for instability. And, if there is any doubt, the answer is to avoid slopes steeper than 30 degrees. Today, the danger is rated MODERATE.</span></span></span></p>
<p>Persistent weak layers buried in the snowpack in Island Park make avalanches failing deep within this winter’s snowpack possible. On a recent ride, I found sugary facets buried in two layers, 18 to 24 inches deep and near the bottom of the snowpack (<a href="https://www.youtube.com/watch?v=j54LPGBrmkg&list=PLXu5151nmAvTi1DBS…;). Yesterday, a group of seven riders near Taylor Mountain triggered a collapse or “whumph” while sitting in flat terrain. This is a red flag because they essentially triggered an avalanche on a persistent weak layer, but their location wasn’t steep enough to slide (<a href="https://www.mtavalanche.com/node/27477"><strong><span>observation</span…;). Thank you for the observation! Contribute to Island Park avalanche information by <a href="https://www.mtavalanche.com/node/add/snow_obs"><span>submitting your observations on the website</span></a>.</p>
<p>Carry and practice with a beacon, shovel, and probe. Dig and test for instability. And, If there is any doubt, the answer is to avoid slopes steeper than 30 degrees.</p>
Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar.
Widespread surface hoar in Hyalite observed up to 8200ft, mostly on E and NE aspects
Had seven sleds in a relatively small area on the south-facing side of Taylor mountain at about 10k ft.
Group noticed a substantial whumph after sitting for less than a minute.
The snow rangers from the Hebgen Lake Distract standing on the debris of a large avalanche near the Airplane Bowl at Lionhead Area. Photo: GNFAC