19-20

<p>The avalanche equation in Cooke City is simple. Heavy snow and wind in the last 24 hours will result in avalanches today. The mountains received 10” of snow last night adding up to .9” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</a> (swe) and winds are gusting up to 40 mph on ridgetops. Ian explains avalanche precautions on storm days like this in his <a href="https://www.youtube.com/watch?v=2JZIsEvkGYY&amp;list=PLXu5151nmAvSbcbVf…;. You are very likely to trigger avalanches in wind loaded areas and likely to trigger slides everywhere else. Avalanches within the new snow will be large and it is possible to trigger slides breaking deeper into the snowpack like those on Henderson and Chimney Rock ten days ago (<a href="https://www.mtavalanche.com/node/21368"><strong>photos</strong></a&gt;). Stick to low angle slopes today and avoid flat areas underneath avalanche terrain. The avalanche danger is rated HIGH on wind loaded slopes and CONSIDERABLE in all other areas.</p>

<p>3-8” of new snow favored the area around West Yellowstone and winds gusting 35-40 mph will stress the weak snowpack in the Lionhead, Southern Gallatin, and Southern Madison Ranges. Yesterday in the Taylor Fork, my partner and I found the weak structure that is consistent in the mountains from Big Sky through West Yellowstone (<strong><a href="https://www.youtube.com/watch?v=QoHpKz6J52s&amp;list=PLXu5151nmAvSbcbVf…;, </strong><a href="https://www.youtube.com/watch?v=Ww-vCQEg-wA"><strong>Bacon Rind video</strong></a>, <a href="https://www.youtube.com/watch?v=kuqUUzl0Wj8"><strong>Lionhead video</strong></a>). On Friday, the GVSA groomer was collapsing flat slopes and falling into the weak facets at the bottom of the snowpack. Today, human triggered avalanches are likely and conservative decision-making is essential. Stay off steep slopes and give extra distance to areas where the wind is creating fresh drifts of snow. The avalanche danger is CONSIDERABLE.</p>

<p>It was an exciting weekend in the Northern Madison, Bridger, and Northern Gallatin Ranges. Riders in Second Yellowmule triggered an avalanche that broke 10 feet deep from low on the slope, partially burying two people (<a href="https://www.mtavalanche.com/node/21453"><strong>details</strong></a&gt;). Doug and Alex visited the site on Sunday and captured some breathtaking photos (<a href="https://www.mtavalanche.com/images/20/snowmobile-triggered-avalanche-bu…;, <a href="https://www.mtavalanche.com/images/20/snowmobile-triggered-avalanche-bu…;, <a href="https://www.youtube.com/watch?v=7vDe6LE-nhU"><strong>video</strong></a&…;). A dog-triggered avalanche passed within 150 feet of my partner and me as we ascended out of Middle Basin (<a href="https://www.youtube.com/watch?v=VZD8KZflzXg&amp;feature=youtu.be"><stro…;, <a href="https://www.mtavalanche.com/sites/default/files/2020-01/P1013879.JPG"><…;). And, the Big Sky and Bridger Bowl Ski Patrol triggered large, hard slab avalanches on deep, persistent weak layers during control work (<a href="https://www.mtavalanche.com/images/20/big-sky-patrol-triggered-deep-sla…;, <a href="https://www.mtavalanche.com/images/20/bridger-patrol-triggered-deep-sla…;). Today, avalanches will be harder to trigger and early red flags will be less likely. Approach steep terrain with caution and after a thorough assessment. The danger is rated MODERATE with natural avalanches unlikely and human triggered avalanches possible.</p>

<p>If you get out, please send us your observations no matter how brief. You can fill out an&nbsp;<a href="https://www.mtavalanche.com/node/add/snow_observation"><strong>observat… form</strong></a>, email us (<a href="mailto:mtavalanche@gmail.com"><strong>mtavalanche@gmail.com</strong></a…;), leave a VM at 406-587-6984, or Instagram (#gnfacobs).</p>

<p>Today strong wind and new snow will increase the avalanche danger. New snow will be drifted into fresh slabs that are possible to trigger. The weight of these fresh drifts may break avalanches deeper in the snowpack, similar to those triggered by snowmobilers last weekend (<strong><a href="https://www.mtavalanche.com/node/21368">photos</a></strong&gt;). Over the weekend skiers near Cooke City observed cracking, settling and unstable test scores below the new snow that fell since Wednesday (<strong><a href="https://www.mtavalanche.com/node/21485">details</a></strong&gt;, <strong><a href="https://www.mtavalanche.com/images/20/sheep-creek-profile-5-jan">snowpi…;). Last Thursday Ian found weak layers below the 1-2 feet of new snow, and he warned to give them time to stabilize (<strong><a href="https://youtu.be/pStZS8rCbJ0">video</a></strong&gt;). Natural avalanches are possible, especially on slopes where thick drifts grow through the day. Avoid steep slopes and be extra cautious below slopes being rapidly loaded by wind-drifted snow. Avalanche danger is CONSIDERABLE.</p>

<p>Saturday, on Buck Ridge near Big Sky a snowmobiler triggered a very large avalanche that partially buried two other riders (<u><strong><a href="https://www.mtavalanche.com/node/21453">details</a></strong></u&gt;). Yesterday Doug and I visited the slide and were wide eyed when we approached the 10 foot deep crown (<strong><a href="https://www.mtavalanche.com/images/20/snowmobile-triggered-avalanche-bu…;, <strong><a href="https://www.mtavalanche.com/images/20/snowmobile-triggered-avalanche-bu…;, <strong><a href="https://www.youtube.com/watch?v=7vDe6LE-nhU">video</a></strong&gt;). Dave was at Beehive Basin where he witnessed a dog break a massive cornice that sent a large avalanche down the slope below (<strong><a href="https://www.youtube.com/watch?v=VZD8KZflzXg&amp;feature=youtu.be">video…;, <strong><a href="https://www.mtavalanche.com/sites/default/files/2020-01/P1013879.JPG">p…;). The dog was okay. Today similar avalanches are possible to trigger, but do not expect similar lucky outcomes.</p>

<p>Weak layers buried deep in the snowpack were overloaded by snow and strong wind last week, and large avalanches were triggered and broke naturally. See our <u><strong><a href="https://www.mtavalanche.com/photos?field_advisory_year_target_id=438&am… page</a></strong></u> and <u><strong><a href="https://www.mtavalanche.com/avalanche-activity">avalanche activity log</a></strong></u> for a comprehensive view of types of slides that are possible to trigger today. Avoid heavily wind loaded slopes, identifiable by large overhanging cornices or big round pillows of snow, stay far back from the edge of cornices (tell your dog), and avoid steep slopes where you suspect buried persistent weak layers.</p>

<p>Strong wind will continue today&nbsp;and drift snow into fresh slabs. Danger will increase through the day. Natural avalanches are possible on wind loaded slopes and human triggered avalanches are possible on all steep slopes. Avalanche danger is CONSIDERABLE on wind loaded slopes and MODERATE on other steep slopes.</p>

<p>If you get out, please send us your observations no matter how brief. You can fill out an&nbsp;<u><strong><a href="https://www.mtavalanche.com/node/add/snow_observation">observation form</a></strong></u>, email us (<u><strong><a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a></strong></u&gt;), leave a VM at 406-587-6984, or Instagram (#gnfacobs).</p>