Avalanche triggered by snowmobilers in the Little Belts on Thursday (1/10). This is outside of our advisory area, but shows many of the mountains in Montana have a weak and unstable snowpack. Photo: N. Boyer
Avalanche triggered by snowmobilers in the Little Belts on Thursday (1/10). This is outside of our advisory area, but shows many of the mountains in Montana have a weak and unstable snowpack. Photo: N. Boyer
<p>In the mountains near West Yellowstone and the southern Madison and Gallatin ranges it is possible to trigger avalanches 2-3’ deep that break on weak, sugary facets at the base of the snowpack. I rode into Lionhead Ridge on Friday and saw the remnants of five large natural and snowmobile triggered avalanches that are similar to what can be triggered today (<strong><a href="https://www.youtube.com/watch?v=b3LBdamYYvU&t=0s&list=PLXu5151n…;, <strong><a href="https://www.mtavalanche.com/node/19639">details</a></strong>, <strong><a href="https://www.mtavalanche.com/node/19672">details</a></strong>). On Thursday in Cabin Creek we found a similar poor snowpack structure that can produce these types of avalanches (<u><strong><a href="https://www.youtube.com/watch?v=BQ6V8-Pdb3M&t=0s&list=PLXu5151n…;, <u><strong><a href="https://www.mtavalanche.com/images/19/buried-weak-layers-cabin-creek">p…;).</p>
<p>Avalanches are becoming less likely without recent snow and wind loading, which makes stability assessment tricky because we see fewer obvious signs like cracking and collapsing or unstable test results. Steep slopes might not break under the weight of the first rider, sometimes allowing a couple to dozens of tracks before someone finds the weak spot. Avoid riding on and directly below slopes steeper than 35 degrees or carefully assess slopes to determine they don’t have a poor snowpack structure. Today, large avalanches are possible to trigger and avalanche danger is MODERATE.</p>
<p>In the mountains near Bozeman, Big Sky and Cooke City it is possible to trigger avalanches that break 1-2’ deep on layers of weak, sugary facets. On Friday, on the south face of Mt. Abundance near Cooke City a snowmobiler triggered an avalanche 1-2' deep and large enough to bury a person (<strong><a href="https://www.mtavalanche.com/node/19684">details</a></strong>, <strong><a href="https://www.mtavalanche.com/images/19/snowmobile-triggered-mt-abundance…;). Yesterday near Big Sky Eric found a weak snowpack and had one low angle slope collapse (<strong><a href="https://www.youtube.com/watch?v=Ryd8fZKwVmo&list=PLXu5151nmAvRNl9ku…;), a sign that avalanches are possible on steeper slopes. The last couple days, skiers in Hyalite <strong>(<u><a href="https://www.mtavalanche.com/images/19/poor-structure-near-lick-creek">p…;, <strong><a href="https://www.mtavalanche.com/images/19/ectp-hyalite">photo</a></strong>) and the Bridger Range (<u><strong><a href="https://www.mtavalanche.com/images/19/weak-snow-northern-bridgers">phot…;) observed a similar poor snowpack structure.</p>
<p>Not all slopes have an unstable and weak snowpack structure. Some are stronger and some are entirely weak, yet stable without a cohesive slab on top. The weakest snow is found where the snowpack is less than 3’ deep (<u><strong><a href="https://www.youtube.com/watch?v=d2uyqO9S4Qw&t=0s&list=PLXu5151n…;, </strong></u><u><strong><a href="https://www.youtube.com/watch?v=cljvf0-9vyU&list=PLXu5151nmAvRNl9ku…;). Carefully assess the snowpack and consequences of a slide before riding steep slopes. Today, buried weak layers make avalanches possible to trigger and avalanche danger is <strong>MODERATE</strong>.</p>
<p>If you get out and have any avalanche or snowpack observations to share, contact us via our <u><a href="https://www.mtavalanche.com/node/add/snow_observation">website</a></u>, email (<u><a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a></u>), phone (406-587-6984), or Instagram (#gnfacobs).</p>
On Wednesday, a snowmobiler was killed in an avalanche on Togwotee Pass northeast of Jackson Hole. Preliminary details from the Bridger Teton Avalanche Center can be found here. The BTAC will have an updated accident report in the near future. This is the third U.S. avalanche fatality in the past week. Our condolences go out to the friends and family of the victim.
A rider experienced cracking on the edge of their tracks in Cabin Creek in the southern Madison Range. This is a sign of a poor, unstable snowpack structure. Photo: M. Lanterman
From e-mail: "We dug our pit upon crossing into the northern aspect of Twin Falls Basin. We had observed a few, small avalanches across the basin on Mount Bole and decided to dig a pit before skiing the northern aspect. We observed an ECTP 17 and decided to cross back over the ridge and ski out the rather sun crusted south facing aspect. Very faceted snow and large wind slabs were observed during the entire tour." Photo: M. Beck
A snowmobiler triggered this avalanche on Friday afternoon (1/11) on Mt. Abundance north of Cooke City. It broke into old snow, and is on a south aspect at 10,000'.
A snowmobiler triggered this avalanche on Friday afternoon (1/11) on Mt. Abundance north of Cooke City. It broke into old snow, and is on a south aspect at 10,000'.
A snowmobiler triggered this avalanche on Friday afternoon (1/11) on Mt. Abundance north of Cooke City. It broke into old snow, and is on a south aspect at 10,000'.
