24-25

<p>Human-triggered avalanches failing on weak layers of faceted snow in the lowest 1-2 feet of the snowpack are possible in the mountains around West Yellowstone and Cooke City and in the Southern Gallatin and Southern Madison Ranges.</p>

<p>Large <strong>persistent slab avalanches</strong> are becoming less likely and the most recent known slides occurred one week ago (<a href="https://www.mtavalanche.com/node/33584"><strong><span>Red Mountain</span></strong></a>, <a href="https://www.mtavalanche.com/node/33544"><strong><span>Woody Ridge 1</span></strong></a>, <a href="https://www.mtavalanche.com/node/33528"><strong><span>Woody Ridge 2</span></strong></a>). However, a rider near Cabin Creek sent in a video of knee-deep, shooting cracks propagating across the slope on Sunday (<a href="https://www.mtavalanche.com/node/33790"><strong><span>photos</span></st…;). Do not ignore these signs of persistent slab instability. Avalanches are most likely on slopes with significant variations in snow depth where a skier or rider impacts weak layers that fail in shallow areas around rocks or wind-scoured terrain and propagate across a slope. Conversely, avalanches are less likely on slopes with a uniformly deep snowpack.</p>

<p><strong>Wind slab avalanches</strong> are possible where snow drifts onto steep slopes. Yesterday, riders in Cooke City noted a natural avalanche within the wind-drifted snow on Henderson Mountain that broke up to two feet deep (<a href="https://www.mtavalanche.com/node/33806"><strong><span>details</span></s…;).</p>

<p><strong>If you consider traveling on slopes steeper than 30 degrees</strong>, choose non-wind-loaded terrain with relatively deep and consistent snow cover. Follow safe travel practices, ensuring all party members carry a beacon, shovel, and probe and only expose one person at a time to hazardous slopes.</p>

<p><span>The avalanche danger is MODERATE.</span></p>

<p>In the mountains near Bozeman, Big Sky and Island Park, <strong>wind slab avalanches</strong> are possible on steep slopes with recent drifts of wind-loaded snow. Avalanches are unlikely in non-wind-loaded terrain.</p>

<p>Strong winds are drifting snow into slabs several inches to a few feet thick. On Sunday, Alex and Haylee toured north of Bridger Bowl, triggering thin wind slabs on small test slopes (<a href="https://www.youtube.com/watch?v=19A0eFtksEQ"><strong><span>video</span>…;, </strong><a href="https://www.mtavalanche.com/node/33779"><strong><span>observation</span…;). Local ski patrols triggered avalanches on wind-loaded slopes during frosty avalanche mitigation work, and backcountry travelers reported “reactive wind slabs up to 30 inches deep” in the Bridger Range (<a href="https://www.mtavalanche.com/node/33804"><strong><span>observations 1</span></strong></a><strong>, </strong><a href="https://www.mtavalanche.com/node/33803"><strong><span>2</span></strong>…;). Use visual clues of drifting and signs of instability, such as cracking or a stiffening of the snow surface, to identify and avoid problem areas (<a href="https://www.mtavalanche.com/images/25/shooting-crack-jefferson-17-jan-2…;, <a href="https://www.mtavalanche.com/images/25/cracking-shallow-wind-drift"><str…;). Even a small wind slab may have significant consequences in steep or extreme terrain.</p>

<p><strong>Persistent Slab Avalanches</strong> breaking on weak layers near the bottom of the snowpack are unlikely. However, isolated areas of instability exist. On Sunday, skiers found a poor snowpack structure and experienced multiple collapses in a shallow snowpack near Fairy Lake (<a href="https://www.mtavalanche.com/node/33788"><strong><span>observation</span…;).</p>

<p><span>While following safe travel practices, seek out slopes <em>sheltered from the effects of the wind</em> with a <em>uniformly deep</em> snowpack, as these will be the safest. The avalanche danger is MODERATE on wind-loaded slopes and LOW on other slopes.</span></p>