18-19

<p>The snowpack depth in the mountains near West Yellowstone and south of Big Sky is below average. In most locations, the pack is 2-3’ deep and consists of sugary facets near the ground. This persistent weak layer is widespread and continues to be our main avalanche concern.</p>

<p>Human triggered avalanches remain possible, primarily on slopes where older slabs of wind deposited snow rest over the weak faceted foundation. The best defense against a pervasive weak layer problem is careful terrain management. It’s best to keep slope angles less than 30 degrees and avoid recreating on slopes attached to steep slopes above. If you do travel into avalanche terrain, carry the proper rescue gear, only expose one person at a time to steep slopes, and always watch your partner from a safe location.</p>

<p>Today, a poor snowpack structure makes all steep slopes susceptible to human triggered avalanches and the avalanche danger is rated <strong>MODERATE</strong>.</p>

<p>The snowpack is highly variable in the mountains around Cooke City. North of town, a layer of facets 1-1.5’ below the surface is the main avalanche concern. Doug found this layer to be reactive in stability tests on Wednesday (<u><strong><a href="https://www.youtube.com/watch?v=W6iS9ManzPo&amp;index=2&amp;list=PLXu51…;, <u><strong><a href="https://www.mtavalanche.com/images/18/instability-near-lulu-pass">photo…;). The tricky part about this layer is it does not exist on every slope and has not been overly reactive. The only way to assess the strength and distribution of this weak layer is dig a snowpit and do a stability test. If test results point to instability, stick to lower angle terrain or find a slope with a stronger structure. &nbsp;</p>

<p>South of town, the snowpack is shallower and weaker. Yesterday, Doug toured up Republic Creek and found facets in the lower portion of the pack to be his main concern. This weak layer is not under a lot of stress without new snow and wind, but will be problematic&nbsp;with the next significant loading event.</p>

<p>Today, buried weak layers make human triggered avalanches possible and the avalanche danger is rated <strong>MODERATE</strong>.</p>

<p>Over the past 24 hours, the Bridger Range picked up 4-6” of low density snow (cold smoke). This did not add a lot of weight/stress to the snowpack, but it did create new snow instabilities. Yesterday, Alex toured on the Throne in the northern Bridgers and found loose dry avalanches (sluffs) and soft wind slabs to be the main avalanche problems (<strong><a href="https://www.youtube.com/watch?v=nmkEoBQ6X_0&amp;list=PLXu5151nmAvRNl9ku…;, <a href="https://www.mtavalanche.com/images/18/low-density-new-snow-bridgers">ph…;). Today, sluffs and soft slabs will be possible to trigger on all steep slopes. For this reason, the avalanche danger is rated <strong>MODERATE</strong> in the Bridger Range.</p>

<p>The northern Gallatin (Hyalite) and northern Madison (Big Sky) Ranges&nbsp;picked up 1-2” of&nbsp;snow&nbsp;the past few days. This new snow has been pushed around by west-northwest winds in upper elevation terrain. As a result, small wind slabs have formed in isolated areas. These fresh slabs won’t be exceptionally large, but could catch you off guard if you’re not paying attention. Be especially aware of this problem if you’re skiing or riding in steep, high consequence terrain. Aside from&nbsp;isolated wind slabs, the snowpack is generally stable (<u><strong><a href="https://www.youtube.com/watch?v=2lO7K1Y-gOs&amp;index=4&amp;list=PLXu51…;

<p>Today, human triggered avalanches are possible on wind loaded slopes which have a <strong>MODERATE</strong> avalanche danger. Non-wind loaded slopes have a <strong>LOW</strong> avalanche danger.</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>In the mountains south of Big Sky and near West Yellowstone, the snowpack is weak but not highly unstable. Without a recent loading event, facets near the ground are not overly stressed. The last reported activity was audible collapsing at Bacon Rind in the southern Madison Range on the 22^nd of December (<u><a href="https://www.mtavalanche.com/node/19372">details</a></u&gt;). Similar activity was reported south of our forecast area in the Centennial Range on the 23^rd (<u><a href="https://www.mtavalanche.com/node/19391">details</a></u&gt;).</p>

<p>Avalanches are becoming less likely without new snow and wind. However, a poor snowpack structure continues to make slides possible. Slopes with wind drifted snow are the most likely to produce unstable conditions. Since weak facets near the ground exist on all aspects and elevations, it’s important to pay attention to surface conditions on the slope you want to ski or ride. If the snow feels firm, punchy, slabby, or all the above, stay off steep slopes and move to more sheltered terrain. The avalanche fatality south of Jackson Hole earlier in the week is a sobering reminder it only takes a small slide to create a potentially deadly situation (<u><a href="http://jhavalanche.org/eventDetail/event/15743">accident report</a></u>). &nbsp;&nbsp;&nbsp;</p>

<p>Today, a poor snowpack structure makes all steep slopes susceptible to human triggered avalanches. For this reason the avalanche danger is rated <strong>MODERATE</strong>.</p>

<p>In the past week, the mountains around Cooke City have picked up over a foot of snow totaling more than 1.5” of SWE (<a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</a>). This incremental load is adding stress to a layer of facets buried 1-2’ feet deep. This weak layer formed in early December and exists on all aspects and elevations. Yesterday, Doug found this layer to be reactive in stability tests near Lulu Pass (<strong><a href="https://www.youtube.com/watch?v=W6iS9ManzPo&amp;index=2&amp;list=PLXu51…;, <strong><a href="https://www.mtavalanche.com/images/18/instability-near-lulu-pass">photo…;). This is consistent with Alex’s observations from last week (<strong><a href="https://www.youtube.com/watch?v=u520iMxlXOQ&amp;index=7&amp;list=PLXu51…;). &nbsp;</p>

<p>Slopes with wind drifted snow will be the most likely to hold unstable conditions, but non-wind loaded slopes also hold the potential to produce slides. Today, carefully evaluate the snowpack before committing to avalanche terrain and always be thinking about the consequences of triggering a slide.</p>

<p>Today, human triggered avalanches are possible on all steep slopes and the avalanche danger is rated <strong>MODERATE</strong>.</p>

<p>In the mountains around Bozeman and Big Sky, the snowpack is generally strong and stable (<strong><a href="https://www.youtube.com/watch?v=2lO7K1Y-gOs&amp;index=4&amp;list=PLXu51…;). Yesterday, I skied Divide Peak in Hyalite and observed no signs of instability (<strong><a href="https://www.youtube.com/watch?v=HkbjuWGKUQI&amp;index=3&amp;list=PLXu51…;). I did find 6-8” of low density snow that will easily be transported by light to moderate winds.</p>

<p>Today, wind loaded slopes are the main avalanche concern. Watch for soft wind drifts on slopes loaded by west-northwest winds. These drifts will be relatively small in size, but could catch and carry a skier or rider into unfavorable terrain. Most avalanches will stay confined to the new snow, but slides breaking on facets buried 1-1.5’ deep are also possible. This layer continues to produce unstable test results on slopes with thick slabs of wind drifted snow. Although this layer is not highly reactive, it’s worth assessing before riding steep terrain.</p>

<p>Today, human triggered avalanches are possible on wind loaded slopes which have a <strong>MODERATE</strong> avalanche danger. Non-wind loaded slopes have a <strong>LOW</strong> avalanche danger.</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>