17-18

<p>Near Bozeman and Big Sky, yesterday’s storm delivered 7-10” of low density snow equal to .3-.5” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</a> (SWE). I was in Hyalite yesterday where there was minimal wind and the main concern was soft slabs of new snow and dry loose avalanches on steep terrain (<strong><a href="https://youtu.be/7RTIXnPxSDQ">video</a></strong&gt;). Today, strong westerly winds will drift new snow into slabs that are easy to trigger. These slabs could be 2-3 feet thick, and found near ridgelines as well as along the edges of cliffs and gullies. Avoid steep, wind-loaded terrain today.</p>

<p>On non-wind loaded slopes, soft slabs of new snow and dry loose avalanches are possible. These avalanches could run far and wide in very steep terrain, and on slopes where the previous snow surface is weak. On some slopes the new snow buried weak facets that formed during recent high pressure (<a href="https://www.mtavalanche.com/images/17/small-faceted-grains"><strong>pho…;, <a href="https://www.mtavalanche.com/images/17/unstable-test-results-west-side-b…;, <a href="https://www.youtube.com/watch?v=b30nRjneTlE"><strong>video</strong></a&…;). Watch for signs of instability such as cracking and collapsing, and avoid slopes similar to where these signs are present.</p>

<p>Today, fresh wind slabs are easy to trigger and the avalanche danger is <strong>CONSIDERABLE</strong> on wind loaded slopes and <strong>MODERATE</strong> on all other slopes.</p>

<p>The mountains near West Yellowstone and Cooke City got 2-3” of low density snow yesterday. Moderate westerly winds will drift this snow into slabs up to a foot thick that are possible to trigger today. These slabs are most likely found near ridgelines. Evaluate terrain for the consequences of being caught in even a small slide. Approach wind loaded slopes with caution or avoid them altogether.</p>

<p>On non-wind loaded slopes the snowpack is generally stable and avalanches are not likely. The recent snow buried weak layers on some slopes, which will be a future problem, but pose minimal threat today without a significant load (<a href="https://www.mtavalanche.com/images/17/small-faceted-grains"><strong>pho…;, <strong><a href="https://www.mtavalanche.com/images/17/thin-and-faceted-pika-point">phot…;). Today, the avalanche danger is <strong>MODERATE</strong> on wind loaded slopes and <strong>LOW</strong> on non-wind loaded slopes.</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>This storm looks to be weaker than originally forecasted. By the time it’s over, the mountains will likely pick up 3-5” of low density snow. This won’t add a significant amount of stress to the snowpack, but it will be enough produce heightened avalanche conditions. On some slopes, the new snow is being deposited on a weak layer of near surface facets that formed during the recent high pressure. Alex and I found this layer on the west side of the Bridger Range (<a href="https://www.mtavalanche.com/images/17/small-faceted-grains"><strong>pho…;, <a href="https://www.youtube.com/watch?v=b30nRjneTlE"><strong>video</strong></a&…;) and I also found it in the Lionhead area near West Yellowstone yesterday. It’s safe to say this persistent weak layer exists throughout the advisory area (<a href="https://www.mtavalanche.com/images/17/unstable-test-results-west-side-b…;).</p>

<p>Today, human triggered avalanches will be possible on wind loaded and non-wind loaded slopes. In areas where the new snow has been deposited over a weak old snow surface, it will be possible to trigger small soft slab avalanches&nbsp;in steeper terrain. These slides won’t carry a tremendous amount of volume, but they could easily catch and carry a skier or rider into unfavorable terrain. Watch for signs of instability such as cracking/collapsing and avoid slopes where these signs are present.</p>

<p>Fortunately, this storm did not arrive with a heavy amount of wind, so wind loading won’t be a major concern. There will be small isolated wind slabs near the ridgelines, but these should be easy to recognize and avoid. In the Bridger Range, wind slabs that formed prior to this storm could still be a problem. On Thursday, a skier triggered a wind slab on the Football Field south of Bridger Bowl that ran over the cliffs hundreds of feet below. Today, these older slabs should be more stubborn, but they’re something to keep in mind when traveling in the backcountry around the Bridgers. In all areas, manage you’re terrain carefully.</p>

<p>Today, human triggered avalanches are possible and the avalanche danger is rated <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>