18-19

<p>No avalanches have been reported in the southern mountains over the past four days. The reason for the decline in activity is the absences of a recent loading event. Although the snowpack is well adjusted and avalanches are becoming less likely, they still remain possible. The primary avalanche concern is a persistent weak layer of facets buried a foot or two off the ground. This layer has been the culprit for numerous large avalanches over the past ten days (<u><strong><a href="https://www.youtube.com/watch?v=SFA1kKs6wsw&amp;t=0s&amp;index=2&amp;li…;, <u><strong><a href="https://www.mtavalanche.com/node/20160">details and photos</a></strong></u>).</p>

<p>Assessing the strength and distribution of deeply buried weak layers isn’t easy. The best defense against trigging a deep slab avalanche is to avoid riding steep slopes, especially those beneath cornices or in steep rocky terrain.&nbsp; It’s important to remember that tracks on a slope do not indicate stability. If a slide is triggered today, it will&nbsp;likely be large and dangerous. Shallow wind slabs on upper elevation slopes loaded by westerly winds will also be a growing concern as winds increase throughout the day.</p>

<p>Buried weak layers and increasing winds make human triggered avalanches possible and the avalanche danger is rated <strong>MODERATE</strong>.</p>

<p>Wind slabs on upper elevation slopes loaded by west-southwest winds will be the main concern today (<u><strong><a href="https://www.mtavalanche.com/images/19/skier-triggered-avalanche-sheep-m…;). These slabs won’t be exceptionally large, but could break 1-2’ deep. Managing this problem shouldn’t be too difficult. Watch for and avoid areas of wind drifted snow beneath cornices, cliff bands, and cross loaded terrain features. Winds are forecasted to increase through the day making wind slabs more widespread. Active wind loading is a clear indicator instability is on the rise, a warning sign to steer clear of steep wind loaded slopes.</p>

<p>There is an isolated chance a skier or rider could trigger a slide breaking on facets near the ground. Watch for this problem in areas where the snowpack is thinner or on slopes that have been heavily wind loaded. A few a slides earlier in the week are a reminder this problem is still lurking (<u><strong><a href="https://www.mtavalanche.com/images/19/snowmobile-triggered-avalanche-fi…;, <u><strong><a href="https://www.mtavalanche.com/images/19/avalanche-crown-butte-2">photo</a…;, <u><a href="https://www.youtube.com/watch?v=_5mSOkh9iqE&amp;list=PLXu5151nmAvRNl9ku…;

<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>Minimal snow and wind in the southern mountains has allowed the snowpack time to adjust and become more stable. Although avalanches are becoming harder to trigger, they remain a very real concern. If a slide is triggered, it will likely fail on weak layers buried deep in the pack. A large slide triggered in the Lionhead area on Monday is a scary reminder of what remains possible (<u><strong><a href="https://www.youtube.com/watch?v=SFA1kKs6wsw&amp;t=0s&amp;index=2&amp;li…;, <u><strong><a href="https://www.mtavalanche.com/node/20160">details and photos</a></strong></u>). Heavily wind loaded slopes are the most prone to producing deep slab avalanches, but non-wind loaded slopes remain suspect.</p>

<p>Be extra cautious when skiing or riding in steep rocky terrain or near scoured ridgelines where slab margins are thinner. These are likely areas to impact weak layers that could propagate into deeper parts of the slope. Assessing stability on deep weak layers is difficult and avoidance is really the best strategy for dealing with them. Remember that tracks on a slope don’t mean it’s stable, particularly with&nbsp;deep instabilities.</p>

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

<p>Wind loaded slopes are the main concern in the mountains around Bozeman, Big Sky and Cooke City. Yesterday, a skier near Big Sky triggered a small wind slab in a steep alpine chute that subsequently triggered a larger slab as it traveled downhill. Fortunately, the skier was above the slide and not caught. On Monday, a skier triggered a larger slide on a heavily wind loaded slope outside of Cooke City. The skier deployed his airbag and fortunately escaped unharmed (<u><strong><a href="https://www.mtavalanche.com/images/19/skier-triggered-avalanche-sheep-m…;, <u><strong><a href="https://www.mtavalanche.com/node/20159">details</a></strong></u&gt;).</p>

<p>Slides breaking 1-2’ deep in wind-blown are most likely, but there is the potential for slides to step down to weak layers buried deep in the pack. Activity on Buck Ridge and around Cooke City earlier in the week are good examples of this problem (<strong><a href="https://www.mtavalanche.com/images/19/snowmobile-triggered-avalanche-fi…;, <strong><a href="https://www.mtavalanche.com/images/19/avalanche-crown-butte-2">photo</a…;, <a href="https://www.youtube.com/watch?v=_5mSOkh9iqE&amp;list=PLXu5151nmAvRNl9ku…;). Outside of wind loaded slopes the snowpack is generally stable. Yesterday, I skied around the Throne in the northern Bridgers. I found the new snow to be unreactive and well bonded to the old snow surface in non-wind loaded terrain (<strong><a href="https://www.youtube.com/watch?v=DnHKb2KrLxo">video</a></strong>).</p&gt;

<p>Today, the avalanche danger is rated <strong>MODERATE</strong> on wind loaded slopes and <strong>LOW</strong> on all other slopes.</p>