From obs: "2/17 Immediately noticed signs of wind loading and wind slabs on NE-E aspects once in the basin. New cornices have formed in the last couple days along the North ridge to the summit. Cornice collapse on the summit triggered a small wind slab on an isolated slope." Photo: R. Rintala
From obs: "2/17 Immediately noticed signs of wind loading and wind slabs on NE-E aspects once in the basin. New cornices have formed in the last couple days along the North ridge to the summit. Cornice collapse on the summit triggered a small wind slab on an isolated slope." Photo: R. Rintala
From obs: "3 small storm slabs observed on steep terrain of Bridger Ridge (E aspect observed from wolverine woods) Attached is a photo of the deepest likely ~12in crown. No observed wind slab development below 8100ft. No propagating test results in pits dug Lower ramp, and wolverine woods." Photo: L. Butler
From obs" "Observed a few old avalanches today, maybe from the 2/8 storm. Although well out of the advisory area, helpful for skiers in the Red Lodge Area.
1) Silver Falls Cr (Lake Fork), 9200', E, HS-N-R4-D1.5-O 45cm thick pencil hardness slab, HS 135. Pulled out into upper 20 degree terrain. 2-3 avalanches here, with one crown ~600' long.
Climbing at the Unnamed Wall in the vicinity of The Fat One, there are some 3"–8" wind slabs formed. At least three small pockets had released from 2" to 5" deep. Lots of spindrift and heavy winds filled in parts of our trail in a few minutes.
2/17 Immediately noticed signs of wind loading and wind slabs on NE-E aspects once in the basin. New cornices have formed in the last couple days along the North ridge to the summit. Cornice collapse on the summit triggered a small wind slab on an isolated slope.
3 small storm slabs observed on steep terrain of Bridger Ridge (E aspect observed from wolverine woods) Attached is a photo of the deepest likely ~12in crown
No observed wind slab development below 8100ft. No propagating test results in pits dug Lower ramp, and wolverine woods.
<p>There has been a lot of snow recently, and dangerous avalanche conditions exist across the forecast area. Two things have kept us from going to an avalanche warning. First, snow has fallen with little wind. Second, we have a stronger-than-average snowpack this season (see Mark’s <a href="https://www.youtube.com/shorts/O6qlZ9VHs3M"><span>video</span></a>). But make no mistake: if you ski or ride in steep terrain, you will <em>likely</em> trigger an avalanche (<a href="https://www.mtavalanche.com/avalanche-activity"><span>list of recent avalanche activity</span></a>), and that avalanche will <em>likely </em>be large enough to carry, injure or kill you.</p>
<p>Across the forecast area, <strong>wind slab avalanches </strong>on steep wind-loaded slopes are sensitive to human triggers (you). Thankfully, without much wind so far (knock on wood), these unstable wind drifts will be in relatively predictable locations on higher elevation slopes, often above treeline, near ridgelines and below cornices. <em>Avoid all steep slopes</em> you think might be wind-loaded and be watching for signs of instability telling you to back off.</p>
<p>Careful snowpack assessment, cautious route-finding and conservative decision-making are essential to safer travel in non-wind-loaded terrain. During my fieldwork the last two days, I continually evaluated for shooting cracks, scanned hillsides for avalanche activity and dug down a couple of feet below the new snow to assess and test for instability related to buried weak layers (<a href="https://www.youtube.com/shorts/hf1nmcVcC_s"><strong><span>Beehive video</span></strong></a>). Evaluate the potential for <strong>storm slab avalanches </strong>resulting from inconsistencies within the recent snow and <strong>loose snow avalanches </strong>(or sluffs) on steep slopes where the new snow isn’t acting cohesively. Yesterday, skiers north of Bridger Bowl and in Cooke City did a great job recognizing instability and adjusting travel plans to match conditions (<a href="https://www.mtavalanche.com/node/34219"><strong><span>Ramp observation</span></strong></a>, <a href="https://mtavalanche.com/node/34236"><strong><span>Throne observation</span></strong></a>, <a href="https://www.mtavalanche.com/node/34222"><strong><span>Republic Creek observation</span></strong></a>). Even with good evaluation, instability can surprise you as it did with skiers in Hyalite and riders on Buck Ridge (<a href="https://www.mtavalanche.com/node/34210"><strong><span>Elephant Mountain photo</span></strong></a>, <a href="https://www.mtavalanche.com/images/25/snowmobile-triggered-avalanche-bu… photo</span></strong></a>).</p>
<p><strong>Persistent slab avalanches</strong> could break on weak layers buried 2-4 feet deep in the Southern Gallatin and Southern Madison Ranges and the mountains around West Yellowstone, Cooke City and Island Park. Last week in Taylor Fork Alex and I saw four avalanches that broke 1-2 feet deep on layers of sugary facets and feathery surface hoar. This weekend, a rider triggered a small wind slab avalanche at Lionhead that subsequently triggered a deeper persistent slab avalanche (<a href="https://www.mtavalanche.com/node/34208"><strong><span>report</span></st…;). Continued snowfall and wind-loading increase the likelihood of these larger slides<span> </span>(<a href="https://www.mtavalanche.com/node/34156"><strong><span>Lionhead photo</span></strong></a>, <a href="https://www.mtavalanche.com/images/25/cornice-triggered-avalanche-miner… City photo</span></strong></a>,<strong> </strong><a href="https://www.youtube.com/watch?v=wZ3k35z5Ej8&embeds_referring_euri=h… Fork video</span></strong></a>). Test for instability on these buried weak layers before considering any steeper terrain.</p>
<p><span>If you are unsure about the terrain and snowpack assessments described above, or they seem like too much work, avoid terrain steeper than 30 degrees because the danger is rated CONSIDERABLE on all slopes. </span></p>
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0.5/7" Snow at Black Bear SNOTEL
