From email: "Went for a tour today on specimen ridge in yellowstone park. Stuck to terrain well below 30 degrees. Widespread whumphs throughout the tour. Cracking and collapsing snowpack on small convexities. Observed multiple small avalanches on windloaded slopes." Photo: C. Way
Went for a tour today on specimen ridge in yellowstone park. Stuck to terrain well below 30 degrees. Widespread whumphs throughout tour. Cracking and collapsing snowpack on small convexities. Observed multiple small avalanches on windloaded slopes. I believe they were triggered remotely by game.
A nice day going up Avalanche Gulch to Responsible. No signs of instability including a pretty good look up into the Maid of the Mist area. Good stability/structure in the gullies. Snow surfaces got wet on steep rocky solar aspects today.
Skier Triggered a 1.5' slide to his right while making a turn near a cliff band. The slide did not intersect with the skiers path. We did a ECT before choosing our line and were not able to get the soft slab, or anything else to propagate, but clearly the slab is ready to go as it slid on rocks. We both skied out without incident.
I toured up Flanders today, and found a weak, thin snowpack. A pit on an east aspect at 9400’ was 98 cm deep, and failed at ECTP15 on a layer of loose, sugary facets sitting between crusts at 38 cm and 53 cm. The rest of the snowpack seemed relatively solid, but I imagine this layer will take a long while to gain strength.
I did not observe any recent natural activity from the top of Flanders, save for one small slide that started right at a ridgeline, likely from the strong, warm sun we had today. I did not experience any collapsing or cracking, although thinner snow near trees or rocks was weak and unsupportable.
<p>The snowpack in the mountains around West Yellowstone, Big Sky and Bozeman all have a similarly weak structure with a slab of new and wind-drifted snow sitting on top of a weak foundation of sugary facets. A structure like this does not inspire confidence even as the likelihood of human-triggered avalanches goes down as we become further removed from our last snowstorm. The analogy Doug and I made yesterday at Lionhead was that skiing or riding in steep terrain right now is like playing Russian Roulette, but with fewer chambers loaded (<strong><a href="https://www.youtube.com/watch?v=rWeNgK6_PTs&feature=emb_title">vide…;). This analogy applies equally in this portion of our advisory area where we have seen continued signs of instability such as:</p>
<ul>
<li>Two large collapses (“whumps”) and unstable test results on our tour at Lionhead Ridge yesterday</li>
<li>Two large deep slab avalanches triggered by the YC Ski Patrol during yesterday’s avalanche mitigation. One was 600’ wide and 3’ deep, the second broke 5’ deep</li>
<li>Two different tourers reported loud “whumphs” and shooting cracks in the Southern Gallatin Range</li>
<li>A large unintentionally triggered avalanche on the Football Field just south of the Bridger Bowl Boundary on Christmas Day (<a href="https://www.mtavalanche.com/node/23396"><strong>photos and details</strong></a>)</li>
</ul>
<p>These events correspond to what we have observed in the field. Go through this <strong><a href="https://www.youtube.com/playlist?list=PLXu5151nmAvQDzKmH5K3ZS8Gg3DzwsZ3…’s field video library</a></strong> for discussions about our field observations.</p>
<p>Today, utilize thorough snowpack evaluation and careful route selection that avoids steep terrain. Human triggered avalanches remain a scary possibility and the danger is rated MODERATE.</p>
<p>While the danger rating is the same in Cooke City as in our other areas, the avalanche problem is different because the foundation of the snowpack I s generally strong. Human-triggered avalanches failing 2-3’ deep within the new and wind-drifted snow from the last week of snowstorms are possible in steep, rocky terrain. Watch our videos and read about recent avalanche activity to get an idea of what is possible (<a href="https://youtu.be/bHZazXX4EXM"><strong>video</strong></a>, <a href="https://youtu.be/Ava7FSUx9kY"><strong>video</strong></a>, <a href="https://www.mtavalanche.com/node/23352"><strong>details</strong></a>). The new snow will continue to stabilize but remain vigilant by following safe travel protocols and carrying avalanche rescue gear. Today, watch for signs of instability such as shooting cracks and evaluate the upper few feet of the snowpack by digging and performing a stability test before committing to any avalanche terrain. The avalanche danger is rated MODERATE.</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>
Upcoming Avalanche Education and Events
See our education calendar for an up to date list of all local classes. Here are a few select upcoming events and opportunities to check out:
Up Woody Ridge. Single pit at 9000ish, or higher, just before snowpack thins towards tree line before ridge line, was interesting. 1.2 to 1.4 M deep. Layer at 18-24 inches from top that was reactive (at 24 with partial propagation) and another layer about 2 feet from bottom that came out with work. All in all it gave us a reason to think about what seemed to be a no brainer. Glad we dug.
Observed 6-7" of lower density new snow today on Woody Ridge, with maybe 3" or so since last night. There was a crust present on south facing aspects to pretty much the top of Woody. This crust was at times present on north facing aspects also. The new snow was decently bonded to the crust in most places. Dug a pit in a fairly open but sheltered area about 3/4 way up Woody. Dug 3.5-4 feet down and the snowpack appeared fairly locked up following last week's atmospheric river event. No new avalanche activity observed besides what has already been reported (e.g. east face Republic).
Up on the shoulder of Blackmore today. HS 125cm plus or minus, with 15-20cm HST. Poor structure is widespread. No cracking/collapsing/signs of avalanche activity on basal layers. The steep, wind loaded terrain on lookers R of the N Face (NE aspect) slid naturally some time towards the end of the snow event on the interface, around 30 cm estimated depth, some crowns up to 40m across. Nothing ran more than 100m. SS-N-D1R2-I. On the east face, nothing more than size 1 Dry Loose. This round of snow didn't seem to tip the scales around the general Blackmore area but I'm not really trusting larger pieces of terrain in the Hyalite region for the foreseeable future.
