24-25

<p><span><span><span><span><span><span>A person can trigger avalanches 2-4 feet deep, or deeper on some wind-loaded slopes, which break on persistent weak layers near the bottom of the snowpack. You are more likely to trigger these big </span></span></span></span></span></span><span><span><span><strong><span><span>persistent slab avalanches </span></span></strong></span></span></span><span><span><span><span><span><span>on slopes with snow depths less than 3-4 ft deep. On big slopes where snow depth varies you can trigger one of these slides from a thinner area and it can break wide into a deeper part of the slope. Choose slopes that are non-wind-loaded and with a relatively deep and more uniform snow depth, or stay on slopes less than 30 degrees to keep it simple. Recent avalanches show some of the types of terrain to avoid to minimize triggering a persistent slab avalanche (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33584"><span><span><span><strong><span… Mountain</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33544"><span><span><span><strong><span… Ridge 1</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33528"><span><span><span><strong><span… Ridge 2</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>).</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Additionally, </span></span></span></span></span></span><span><span><span><strong><span><span>wind slab avalanches </span></span></strong></span></span></span><span><span><span><span><span><span>can be triggered where the recent snow has been drifted into soft slabs up to 1-2 feet thick. Assess the snowpack for unstable drifts, assess the terrain for consequences like cliffs, trees and gullies, and remember even a small slide can easily knock you down. Human-triggered avalanches are possible and the avalanche danger is MODERATE near Cooke City, West Yellowstone and in the southern Madison and Gallatin Ranges.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Near Bozeman, Big Sky and Island Park </span></span></span></span></span></span><span><span><span><strong><span><span>wind slab avalanches</span></span></strong></span></span></span><span><span><span><span><span><span> can be triggered where recent snow has been drifted into slabs up to a couple feet thick. Watch for drifting snow off ridgelines (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/25/saddle-peak-wind-transport"><span…;) and cracking across the snow surface (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/25/shooting-crack-jefferson-17-jan-2…;) as signs that fresh wind slabs exist. Older drifts of snow that formed over the last week will be more stubborn, but worth watching out for. Note that strong winds last week formed some drifts in less typical locations like lower elevations.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Avalanches breaking on persistent weak layers are unlikely in these parts of our forecast area. However, buried weak layers do exist, so it is worth choosing slopes with a deeper, more uniform snow depth. See our recent observations from </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33746"><span><span><span><span><span><… Park</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span> and </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33742"><span><span><span><span><span><…. Ellis</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>, and </span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=63ynwwMOJ4U"><span><span><span><span><s…’s video</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span> for more info on this unlikely persistent slab problem.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>In the mountains around Bozeman, Big Sky, and Island Park the avalanche danger is MODERATE on wind-loaded slopes and LOW on other slopes. Assess the snowpack for buried weak layers and unstable drifts before committing to steep slopes.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>There are two main avalanche concerns today - avalanches breaking within recently wind-drifted snow and avalanches breaking deep in the snowpack on persistent weak layers 1-2 ft off the ground.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><strong><span><span>Wind Slab avalanches</span></span></strong></span></span></span><span><span><span><span><span><span> are most likely in the areas that have more new snow. Keep an eye out for wind drifts deeper than a couple inches. If you find a drift on a steep slope, either steer around it or assess how well it has bonded to the old snow.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>You’re most likely to trigger a </span></span></span></span></span></span><span><span><span><strong><span><span>Persistent Slab avalanche </span></span></strong></span></span></span><span><span><span><span><span><span>in a thinner snowpack. That could be a lower elevation slope, a thin spot near rocks, or somewhere in the zones around West Yellowstone that generally have a thinner snowpack. While these slides are most likely to start in a thin area, they could propagate out into deeper places and turn into quite a big avalanche. If you want to get into steeper terrain, look for slopes with a uniformly thick snowpack (5+ ft deep) and accept that there is still some possibility you may trigger a slide. Make sure you and your partners all have rescue gear and the rest of your group is watching from a safe spot in case you get unlucky.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Human triggered avalanches are possible and the avalanche danger is MODERATE today.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Around Bozeman and Big Sky, avalanches have become unlikely on slopes unaffected by the wind. With weak layers in the snowpack, there is always some chance of triggering a deeper slide, but you should focus most of your attention on watching out for wind drifts.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>As you travel through the mountains today, you’ll find wind drifts that formed at different times over the last week and are bonded to different degrees. Strong winds a couple days were drifting snow at low elevations and in atypical locations, so stay alert even when you’re not up in the normal loading areas near ridgelines. New drifts will likely be thin, but easier to trigger, while older drifts are potentially thicker, but less likely to avalanche. Carefully assess the depth and bonding of drifts before getting into steep terrain. Cracks shooting out in front of your skis or sled are a clear sign of unstable snow and should lead to a quick retreat off steep slopes.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The avalanche danger is MODERATE on wind loaded slopes and LOW on non-wind loaded slopes.</span></span></span></span></span></span></p>