17-18

<p>The Lionhead area near West Yellowstone has the shallowest and weakest snowpack in the advisory area. Heavy snow two days ago combined with more snow and wind today will create very dangerous avalanche conditions. Yesterday, snowmobile guides from Ace Powder Guides in West Yellowstone found a fragile snowpack willing to propagate fractures easily in stability tests (<strong><a href="https://www.youtube.com/watch?v=Kl0SZcPkP4I&amp;index=2&amp;list=PLXu51…;). Tests were failing on a layer of facets sitting over the Thanksgiving ice crust. This facet/crust combo is the perfect recipe for avalanches on both wind loaded and non-wind loaded slopes.</p>

<p>As more snow and wind impact the area today, the avalanche danger will continue to rise. Given the weak snowpack structure and current loading event, Natural and human triggered avalanches will be likely on wind loaded slopes which have a <strong>HIGH</strong> avalanche danger. Non-wind loaded slopes have a <strong>CONSIDERABLE</strong> avalanche danger.</p>

<p>Yesterday, my partner and I were more surprised by what we didn’t see then what we saw in the Taylor Fork in the southern Madison Range. I was expecting to see natural avalanches in high elevation terrain and to get unstable results in stability tests, but we were 0-2 on these assumptions. We did observe one small natural avalanche in wind loaded terrain, but this slide was not a major red flag (<strong><a href="https://www.mtavalanche.com/photos">photo</a></strong&gt;). We did however find the layer of near surface facets under the new snow, which could become more reactive with the additional weight of today’s storm (<strong><a href="https://www.youtube.com/watch?v=u7_Z88o2aaQ&amp;list=PLXu5151nmAvQSYtIf…;

<p>This scenario also plays true with the mountains around Bozeman, Big Sky and Cooke City. We know there is a layer of facets buried 1-2’ deep with sporadic distribution (<a href="https://www.mtavalanche.com/images/17/weak-facets-are-under-new-snow"><…;, <a href="https://youtu.be/sZxO8CPCcTk"><strong>video</strong></a&gt;). This layer caused cracking/collapsing and recent avalanches in the mountains around Cooke City a few days ago (<strong><a href="https://www.mtavalanche.com/images/17/avalanche-wind-loaded-slope">phot…;). It has also caused signs of instability in the mountains around Bozeman and Big Sky.</p>

<p>As the storm continues today, human triggered avalanches will be likely on all slopes. For this reason, the avalanche danger is rated <strong>CONSIDERABLE</strong>.</p>

<p>If you get out and have any avalanche or snowpack observations to share, drop a line via our <a href="https://www.mtavalanche.com/node/add/snow_observation">website</a&gt;, email (<a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a&gt;), phone (406-587-6984), or Instagram (#gnfacobs).</p>