21-22

<p>The mountains around Cooke City and West Yellowstone and the Southern Madison and Southern Gallatin Ranges picked up 2-3” of new snow bringing the storm totals to 33-40” of new snow in the last week (2.8-3.7” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/null/?cid=nrcseprd1314… water equivalent</a> - SWE). Tragically, two snowmobilers died in an avalanche yesterday on Scotch Bonnet Mountain north of Cooke City (<a href="https://mtavalanche.com/node/25278"><strong>details and photos</strong></a>). Another&nbsp;group of skiers near Henderson Bench reported a natural avalanche likely triggered by a cornice fall that broke 5-6’ deep on buried weak layers near the ground (<a href="https://mtavalanche.com/node/25281"><strong>details and photo</strong></a>).</p>

<p>The same fundamental structure and loading patterns resulting in avalanches near Cooke City exist in the Lionhead area (<a href="https://www.youtube.com/watch?v=qumV6n73pTs&amp;list=PLXu5151nmAvT1nrM2…;), the Southern Madison (<a href="https://www.youtube.com/watch?v=rdVk9B7UbtQ&amp;list=PLXu5151nmAvT1nrM2…;) and the Southern Gallatin Ranges. Human-triggered avalanches are likely where winds from the last week drifted the 3’ of new snow onto steep slopes. Avalanches may break within the layers of new snow and wind-drifted snow or 5-6’ deep on weak layers buried in the lower third of the snowpack. Keep it simple and avoid steep wind-loaded slopes. Avalanches are possible on non-wind-loaded slopes where you should utilize thorough snowpack assessments, consider the consequences of the terrain and follow safe travel protocols.</p>

<p>You can ride and ski safely today. Avalanches occur in terrain that is 30 degrees and steeper or areas immediately below these steep slopes. Utilize an inclinometer and measure slope angles frequently.</p>

<p>The danger is CONSIDERABLE on wind-loaded slopes and MODERATE on all others.</p>

<p>The mountains around Bozeman and Big Sky got 5-9” of new snow in the last two days equal to 0.4-0.6” of SWE. Skiers at Mount Blackmore noted that recent winds had affected the snow surface and concerns about wind-loaded terrain kept them off steep faces. The Big Sky and Bridger Bowl Ski Patrols both triggered 12-24” deep slides on wind-loaded slopes during routine avalanche mitigation with some breaking across a wide area. Today, human-triggered avalanches are possible in wind-loaded terrain. Most likely they would be similar to the natural avalanche on Saddle Peak on Christmas day (<a href="https://www.mtavalanche.com/images/21/natural-avalanche-saddle-peak-1">…;), but weaker layers of snow in the lower in the snowpack could fail on heavily wind-loaded slopes. With less active wind-loading today, look for other clues to identify areas with <em>recent</em> wind-loading such as cornices, snow stiffening under your feet or sled and shooting cracks.&nbsp;</p>

<p>Avalanches are unlikely in non-wind-loaded terrain as we discuss in our videos from <a href="https://www.youtube.com/watch?v=_MhpDHnH8So"><strong>Saddle Peak</strong></a>, <a href="https://youtu.be/cf-qqv2Ssjw"><strong>Buck Ridge</strong></a> and <a href="https://youtu.be/ePMCJs3qAs0"><strong>Beehive Basin</strong></a>. Yesterday, standard safe travel protocols and a good snowpack assessment kept a group of skiers out of steep terrain and away from terrain traps in the Northern Gallatin Range when they found a poor snowpack structure, even though they had stable test results. Utilize these strategies for your mountain travel.</p>

<p>The danger is MODERATE on wind-loaded terrain and LOW elsewhere.&nbsp;</p>

<p>If you get out, please send us your observations no matter how brief. You can submit them via our <a href="https://www.mtavalanche.com/node/add/snow_observation"><strong>website<…;, email (<a href="mailto:mtavalanche@gmail.com"><strong>mtavalanche@gmail.com</strong></a…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>

<p>Consistent snowfall for the last five days brings our storm total to 31-37” equal to 2.6” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/null/?cid=nrcseprd1314… water equivalent</a> (SWE) in the Southern Madison and Southern Gallatin Ranges and 3.5” of SWE in the mountains around West Yellowstone and Cooke City. The combination of recent snow and moderate winds from the southwest creates dangerous avalanche conditions. While the wind will ease off today, recently formed 1-4’ deep drifts will remain unstable. Avalanches failing on weaker layers of snow in the mid and lower snowpack are a possibility and would be large and dangerous. This reality kept Doug and me out of avalanche terrain yesterday at Lionhead (<a href="https://www.youtube.com/watch?v=qumV6n73pTs"><strong>video</strong></a&…;). <a href="https://www.youtube.com/watch?v=rdVk9B7UbtQ"><strong>Alex’s advice from the Taylor Fork</strong></a> and <a href="https://www.youtube.com/watch?v=4GrVPi-1FC8&amp;list=PLXu5151nmAvT1nrM2… from last week in Cooke City</strong></a> holds true today, steer clear of wind-loaded slopes and carefully assess the snowpack and terrain features in non-wind-loaded areas prior to entering any avalanche terrain.</p>

<p>With the significant caveat that visibility is limited, we have not seen or received reports of widespread avalanche activity during this storm. We do have good indicators of instability such as large “whumphs” triggered by skiers near Bacon Rind on Friday (<a href="https://www.mtavalanche.com/node/25253"><strong>details</strong></a&gt;) and unstable snowpack tests throughout the area failing and propagating within new snow layers and on weak layers near the ground. If you see an avalanche in the mountains today, snap a photo and submit it through our <a href="https://mtavalanche.com/node/add/snow_obs"><strong>observations form</strong></a>.</p>

<p>The avalanche danger is rated CONSIDERABLE on wind-loaded slopes where human-triggered avalanches are likely and MODERATE on non-wind-loaded slopes where avalanches are possible</p>

<p>The mountains around Bozeman and Big Sky received 5-8” of new snow equal to 0.3-0.5” SWE during yesterday’s storm with winds from the southwest quickly forming thicker drifts. Let recent signs of instability in wind-loaded terrain such as a natural avalanche on Saddle Peak on Christmas Day guide your travel plans today (<a href="https://www.mtavalanche.com/images/21/natural-avalanche-saddle-peak-1">…;). Remain dedicated to your safe travel protocols and pay attention to changes to the snow under your feet or sled, turning around if you enter a deeper drift, see shooting cracks or the snow surface seems to stiffen. These are the areas where triggering a slab avalanche within the new snow or on deeper weak layers is possible. Human-triggered slides on non-wind-loaded terrain are unlikely today. See our recent field videos from <a href="https://www.youtube.com/watch?v=_MhpDHnH8So"><strong>Saddle Peak</strong></a>, <a href="https://youtu.be/cf-qqv2Ssjw"><strong>Buck Ridge</strong></a> and <a href="https://youtu.be/ePMCJs3qAs0"><strong>Beehive Basin</strong></a> for a further look. Today, the avalanche danger is MODERATE on wind-loaded slopes and LOW on all others.</p>

<p>If you get out, please send us your observations no matter how brief. You can submit them via our <a href="https://www.mtavalanche.com/node/add/snow_observation"><strong>website<…;, email (<a href="mailto:mtavalanche@gmail.com"><strong>mtavalanche@gmail.com</strong></a…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>