17-18

<p>On Sunday, outside Cooke City, skiers triggered two small avalanches (<a href="https://www.mtavalanche.com/images/18/remote-triggered-soft-slab"><stro…;, <a href="https://www.mtavalanche.com/images/18/remote-triggered-soft-slab-0"><st…;), and yesterday another small slide was triggered on a wind-loaded slope (40’ wide; 12-18” deep). Around Lionhead the snowpack remains weaker than other areas from sugary snow near the ground, but it is getting more difficult to trigger avalanches with each passing day. I saw this twice in the last week, once in Lionhead (<a href="https://youtu.be/nQ5ZZBJLC-4"><strong>video</strong></a&gt;), and again this Sunday in Cabin Creek in the southern Madison Range (<a href="https://youtu.be/-5OhvArl2P0"><strong>video</strong></a&gt;). In general, our snowpack in the southern mountains is strengthening.</p>

<p>Wind speeds are 20-40 mph out of the southwest and a few slopes will be wind-loaded. Wind slabs are not widespread, but skiers triggered a small one yesterday and another skier saw a 3’ deep avalanche on a north-facing slope up Republic Creek in Cooke City. For today, human triggered avalanches are possible and the danger is rated <strong>MODERATE</strong> on all slopes.</p>

<p>The mountains near Bozeman and Big Sky are mostly stable. Alex was in the Bridger Range on Saturday and found the new snow was bonded and winds were not forming drifts. In the last two days, strong wind scoured many slopes and reports from ski patrols indicate there is not much loose snow left to blow around. Field observations from the northern Gallatin and northern Madison Ranges all indicate good snow stability. If you went out of you way looking for trouble you might find a small wind pillow near the ridgeline that could avalanche, but in general, avalanches are unlikely and the danger is rated <strong>LOW</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>

<p>Since Friday&nbsp;the mountains near Cooke City got 1.5 to 2 feet of snow equal to 1.5” of snow water equivalent (<a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2…;). West to southwest wind drifted this light powder into 1-3’ deep soft slabs that are easy to trigger. Yesterday, skiers near Cooke City triggered small soft slab avalanches from low angle terrain 10-20 feet away (<strong><a href="https://www.mtavalanche.com/images/18/remote-triggered-soft-slab">photo…;, <strong><a href="https://www.mtavalanche.com/images/18/remote-triggered-soft-slab-0">pho…;). These types of slides are likely today. Be cautious of wind loaded slopes and avoid all steep slopes if you see collapsing or cracking of the snow surface. Stay back from the edge of cornices along ridgelines, and avoid large pillows of snow below.</p>

<p>Avalanches breaking deeper than recent snow are difficult to trigger, but are possible and can be large (<a href="https://www.mtavalanche.com/images/18/avalanches-mt-hornaday-ynp"><stro…;). These are more likely where the snowpack depth is highly variable or relatively shallow. Dig and test stability of a layer of facets 1-2’ above the ground before riding steep slopes.</p>

<p>Snow and wind over the weekend formed slabs that are easy to trigger. The avalanche danger is <strong>CONSIDERABLE</strong> on wind loaded slopes and <strong>MODERATE</strong> on all other slopes.</p>

<p>The mountains near Bozeman, Big Sky and West Yellowstone got 6-10” of new snow over the weekend that was drifted into wind slabs 1-2’ thick. These wind slabs are possible to trigger near ridgelines and along the edges of cliffs and gullies. Be cautious of wind loaded slopes, stay back from the edge of ridgelines to avoid large cornices, and avoid steep slopes directly below.</p>

<p>Doug was in Cabin Creek in the southern Madison Range yesterday and found the weak layer of facets 3-5’ deep to be relatively strong (<strong><a href="https://youtu.be/-5OhvArl2P0">video</a></strong&gt;). Large avalanches on this layer are difficult to trigger, but possible. <u>This weak layer is particularly dangerous and unstable in the Lionhead area near West Yellowstone</u> (<a href="https://youtu.be/nQ5ZZBJLC-4"><strong>video</strong></a&gt;, <a href="https://www.mtavalanche.com/images/18/snowmobile-triggered-avalanche-li…;), and on slopes with a relatively shallow snow depth. Carefully evaluate the snowpack before riding any steep slope, and never expose more than one person at a time to steep slopes or terrain below. Avalanche danger today is <strong>MODERATE</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>

<p>The mountains near Cooke City got 8” of new snow equal to .6” snow water equivalent (SWE), and near West Yellowstone and the southern Madison and Gallatin ranges got 3-4” of new snow equal to .3-.4” SWE. Strong winds drifted this light powder into dense slabs 1-3’ thick that are easy to trigger. Avoid large pillows of snow on steep slopes and near ridgelines. Stay far back from the edge of large cornices along ridgelines, and avoid slopes below them. Ski and ride in terrain sheltered from the wind.</p>

<p>Almost a foot of low density snow near Cooke City makes dry loose avalanches and storm slabs possible. Avoid steep slopes if you experience collapsing or see shooting cracks across the snow surface.</p>

<p>Avalanches breaking 3-5' deep on a layer of weak facets are becoming difficult to trigger, but are large and destructive (<strong><a href="https://www.mtavalanche.com/images/18/avalanches-mt-hornaday-ynp">photo…;, <a href="https://www.youtube.com/playlist?list=PLXu5151nmAvQSYtIfyQP-gMYrlfja6Ls…;). This weak layer of facets 1-2’ off the ground is particularly dangerous and unstable in the Lionhead area near West Yellowstone (<a href="https://youtu.be/nQ5ZZBJLC-4"><strong>video</strong></a&gt;, <strong><a href="https://www.mtavalanche.com/images/18/snowmobile-triggered-avalanche-li…;). Be extra cautious of steep slopes and runout zones below. If necessary to cross avalanche terrain never expose more than one person at a time.</p>

<p>Avalanche danger today is <strong>CONSIDERABLE </strong>on wind loaded slopes and <strong>MODERATE</strong> on all other slopes.</p>

<p>The mountains near Bozeman and Big Sky got 1-2” of new snow since yesterday and 4-6” since Thursday. Strong west-southwest wind drifted this snow into slabs 1-2’ thick that are possible to trigger near ridgelines and along the edges of cliffs and gullies. Avoid steep terrain if you see cracking or collapsing of fresh drifts. Avoid terrain traps like cliffs, trees, and confined gullies to minimize the consequences of being caught in any size slide.</p>

<p>Avalanches breaking deeper than fresh wind slabs are not likely, but possible in specific terrain. A buried layer of sugary, weak facets 1-2’ off the ground can produce large avalanches, and it is most unstable where the snowpack is relatively shallow or highly variable. Careful snowpack evaluation is essential before riding any steep slope. On Friday I found an isolated weak layer of surface hoar that was only visible after it produced an unstable result in a stability test (<a href="https://youtu.be/gKvrr5JHODA"><strong>video</strong></a&gt;), which gave good reason to ride different or low angle terrain.</p>

<p>Strong wind and recent snow make avalanche possible and avalanche danger today is <strong>MODERATE</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>