18-19

<p>Last night the Bridger Range received 7-9” of snow equal to .7-1.3” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</a> (SWE). This heavy new snow fell on buried weak layers and firm crusts, and it will be drifted into thick slabs that are easy to trigger or can break naturally. On Friday a solo skier got partially buried in an avalanche near Fairy Lake (<strong><a href="https://www.mtavalanche.com/node/19732">details</a></strong&gt;, <strong><a href="https://www.mtavalanche.com/images/19/avalanche-crown-bridger-range">ph…;), and natural slides were observed on saddle peak (<strong><a href="https://www.mtavalanche.com/node/19741">details</a></strong&gt;). Eric went to Fairy Lake yesterday and found unstable 8-12” thick wind slabs over weak facets.</p>

<p>The new snow will create dangerous avalanche conditions, and the best skiing since 2018. A scary combination. Signs of instability like cracking, collapsing and natural avalanches will be clues that the snowpack is unstable. In the absence of these clues, I would still resist the temptation to ride steeper slopes and let the snowpack adjust. Avoid travel on and underneath avalanche terrain today. Avalanche danger is <strong>HIGH</strong> on wind loaded slopes and <strong>CONSIDERABLE</strong> on all other steep slopes.</p>

<p>The mountains near West Yellowstone and south of Big Sky have the weakest snowpack in the advisory area. The base of the snowpack is 1.5’ of weak, sugary facets (<u><strong><a href="https://www.youtube.com/watch?v=3Y_F3uaJKvI&amp;t=0s&amp;list=PLXu5151n…;). Avalanches can break 2-3’ deep on this weak layer, and can propagate far and wide. It is possible to trigger these slides from lower angle terrain below steep slopes, and they are more likely on wind loaded slopes (example: <u><strong><a href="https://www.mtavalanche.com/images/19/skier-triggered-near-taylor-fork"…;, <u><strong><a href="https://www.mtavalanche.com/node/19716">details</a></strong></u&gt;). Avoid travel on and underneath steep slopes today. Human triggered avalanches are likely and avalanche danger is <strong>CONSIDERABLE</strong>. Danger could rise to <strong>HIGH</strong> on wind loaded slopes with steady snow and wind today.</p>

<p>I visited Cooke City the last couple days to assess how the snowpack took the weight of 10-12” of new snow (<u><strong><a href="https://www.youtube.com/watch?v=tNPre5Xu2yE&amp;t=0s&amp;list=PLXu5151n…;). The snowpack was generally strong where it is deeper than three feet, and the new snow was not yet unstable on shallower weak areas (less than 3’). This is good news, but more snow today and tonight will continue to test the strength of the snowpack. Avalanches are likely to be triggered where the new snow is drifted into thick slabs, and with more snow today&nbsp;avalanches may become easy&nbsp;to trigger on all steep slopes. Avalanche danger is <strong>CONSIDERABLE</strong> on wind loaded slopes and <strong>MODERATE</strong> on all other slopes. Danger may rise to <strong>CONSIDERABLE</strong> on all slopes with steady snowfall today.</p>

<p>The mountains south of Bozeman and near Big Sky received the least snow with 6-7” of snow since Thursday. Avalanches are possible to trigger where wind has drifted this snow into fresh slabs. Avalanches can break larger on weak layers buried 1.5-2’ deep (<u><strong><a href="https://www.youtube.com/watch?v=Ryd8fZKwVmo&amp;list=PLXu5151nmAvRNl9ku…;, <u><strong><a href="https://www.youtube.com/watch?v=VnA2ZhT8vzY&amp;list=PLXu5151nmAvRNl9ku…;). On non-wind loaded slopes, loose snow and slab avalanches of new snow are possible. Carefully assess the snowpack and consequences of being caught in a slide before riding steep slopes. Avalanche danger today 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&gt;, email (<u><a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a></u&gt;), phone (406-587-6984), or Instagram (#gnfacobs).</p>

<p>The snowpack has had some time to adjust to the recent loading event. This does not cancel the fact a poor snowpack structure exists on all aspects and elevations (<u><strong><a href="https://www.youtube.com/watch?v=3Y_F3uaJKvI&amp;t=0s&amp;list=PLXu5151n…;). Slopes that received wind drifted snow the past few days will be the most likely to hold unstable conditions. Slides have to potential to break 2-3’ deep and propagate wider than you might expect (<u><strong><a href="https://www.mtavalanche.com/images/19/skier-triggered-near-taylor-fork"…;, <u><strong><a href="https://www.mtavalanche.com/node/19716">details</a></strong></u&gt;). Watch for areas of wind drifted snow below ridgelines, cliff bands, and cross loaded terrain features.</p>

<p>While big slopes have the potential to create big slides, small slopes can also be dangerous. Be extra cautious when riding small steep slopes in the woods or near gullies where the consequences of triggering a slide are amplified. Always travel one at a time in steep terrain and make sure you have a close eye on your partners. &nbsp;</p>

<p>Today, human triggered avalanches are likely on wind loaded slopes which have <strong>CONSIDERABLE</strong> avalanche danger. Non-wind loaded slopes have a <strong>MODERATE</strong> avalanche danger. &nbsp;</p>

<p>Yesterday, Alex and his partner rode north of Cooke City and found 8” of new snow resting over a variety of old snow surfaces. On slopes where the new snow was deposited on a strong snowpack, conditions were generally stable. In areas where the pack was shallow and weak, they got unstable results in stability tests. As Alex describes in his video, wind loaded slopes are the most concerning since they have the heaviest load (<strong><a href="https://www.youtube.com/watch?v=tNPre5Xu2yE&amp;t=0s&amp;list=PLXu5151n…;). &nbsp;Non-wind loaded slopes are more stable, but still hold the potential to produce slides (<strong><a href="https://www.mtavalanche.com/images/19/dry-loose-new-snow-avalanche-cook…;). Make sure and put the shovel in the snow to assess the snowpack structure before committing to avalanche terrain.</p>

<p>Today, dangerous avalanche conditions exist on wind loaded slopes which have a <strong>CONSIDERABLE</strong> avalanche danger. Non-wind loaded slopes have <strong>MODERATE</strong> avalanche danger. &nbsp;&nbsp;</p>

<p>Yesterday, a lone skier on the summer trail above Fairy Lake was caught and partially buried in an avalanche. The skier triggered the slide from low on the slope and was swept 100’ downhill. He came to rest near some trees and was buried up to his chest. Fortunately, the skier was uninjured and able to self rescue. This was a close call that could have ended much worse.</p>

<p>This slide occurred during the loading event, a time when slopes are typically most reactive. Today, conditions won’t be as touchy, but wind loaded slopes still need to be approached with caution. In most cases, avalanches will stay confined to the new snow, but could potentially step down to weak layers buried deeper in the pack (<strong><a href="https://www.youtube.com/watch?v=Ryd8fZKwVmo&amp;list=PLXu5151nmAvRNl9ku…;). Areas where the snowpack is less than 3’ deep are the most likely to harbor buried weak layers capable of producing larger more dangerous slides (<strong><a href="https://www.youtube.com/watch?v=VnA2ZhT8vzY&amp;list=PLXu5151nmAvRNl9ku…;

<p>Today, wind slabs and weak layers make human triggered avalanches possible and the avalanche danger is rated <strong>MODERATE</strong>. &nbsp;</p>