22-23

<p><span><span><span>A person can trigger large to very large avalanches breaking on buried weak layers. The avalanche that killed a snowmobiler on Saturday near Cooke City broke 1.5-4 feet deep on a layer of sugary, faceted snow below a very hard slab (<strong><a href="https://www.youtube.com/watch?v=zjGCqBikpRw&amp;list=PLXu5151nmAvTi1DBS… of site investigation</a></strong>). Snow from the past week was drifted onto the slope to further stress the weak layer towards breaking. Also, a snowmobiler triggered slide on Sheep Mountain near Cooke City broke 1-4 feet deep (<a href="https://www.youtube.com/watch?v=Tsr8x3PCG3s"><strong><span>video</span>…;, <a href="https://www.mtavalanche.com/node/27426"><strong><span>details</span></s…;), and another on Lionhead ridge near West Yellowstone broke 2-4 feet deep (<a href="https://www.mtavalanche.com/node/27430"><strong><span>details</span></s…;). All these avalanches broke on buried persistent weak layers which means similar avalanches continue to be possible until the snowpack has an extended break from the stress of new and wind-drifted snow.</span></span></span></p>

<p><span><span><span>Avalanches of recently wind-drifted snow are also possible to trigger. These could be large enough to bury a person, and especially dangerous if they push you into hazards like trees, rocks, or over cliffs. Yesterday, skiers north of Bridger Bowl changed their plans after finding unstable snowpack test results below a slab of wind-drifted snow (<strong><a href="https://www.mtavalanche.com/node/27454">observation</a></strong&gt;), and there was a natural avalanche on Saddle Peak that involved recent wind-drifted snow (<strong><a href="https://www.mtavalanche.com/images/23/natural-slide-quarter-saddle">pho…;). Today’s east winds will form drifts in less common locations. </span></span></span></p>

<p><span><span><span>The snowpack depth is shallower in northern areas than further south, but the list of avalanche concerns and travel advice is the same. Carefully assess the snowpack on each steep slope you plan to ride or cross. Watch for signs of unstable drifts such as cracking across the snow surface and avoid steep slopes where you suspect buried weak layers exist. Slopes with a relatively shallower snowpack or where the snow depth varies greatly across a slope are the most suspect and first to be avoided, but you should dig and probe to look for buried weak layers before riding or crossing any steep slope. Today, buried weak layers and recently drifted snow make human-triggered avalanches possible and the avalanche danger is MODERATE.</span></span></span></p>

<p><span><span><span>Please share avalanche, snowpack or weather observations via our<a href="https://www.mtavalanche.com/node/add/snow_obs"&gt; </a><a href="https://www.mtavalanche.com/node/add/snow_obs"><strong><span>website</s…;, email (<strong>mtavalanche@gmail.com</strong>), phone (406-587-6984), or Instagram (#gnfacobs). &nbsp;</span></span></span></p>

<p><span><span><span>Near Island Park a person can trigger large to very large avalanches that break on buried weak layers. Dave was riding in the Centennials yesterday and found these weak layers on some slopes, but not all which can make assessment tricky. See Dave's&nbsp;</span></span></span><strong><span><span><span><a href="https://www.youtube.com/watch?v=j54LPGBrmkg&amp;list=PLXu5151nmAvTi1DBS…; for information on what he found and what to do about it. Either avoid steep slopes or dig to look for and assess buried weak layer before entering steep terrain.</span></span></span></p>