17-18

<p>Storm totals for the Lionhead area are close to 20” totaling 2.1” of SWE. This rapid and heavy load has pushed the snowpack past its breaking point making natural and human triggered avalanches likely. Yesterday, a snowmobiler had a close call when he remotely triggered a slide in thick trees and called conditions “very sketchy” (<strong><a href="https://www.mtavalanche.com/images/18/remote-trigger-lionhead">photo</a…;). With more snow and wind since then, conditions will remain hair trigger. Slides are failing on a layer of facets buried 3-4’ deep, which is producing large and dangerous events.</p>

<p>Today, very dangerous avalanche conditions exist and the avalanche danger is rated <strong>HIGH</strong> on all slopes. Avalanche terrain and avalanche runout zones should be avoided.</p>

<p>Storm totals are impressive across the advisory area, see totals below.</p>

<ul>
<li><a href="https://www.mtavalanche.com/weather/stations/bridger-lift">Bridger Bowl</a>: 16” of snow totaling 1.6” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2…;
<li><a href="https://www.mtavalanche.com/weather/stations/shower-falls-snotel-site">… Falls</a> Snotel site, northern Gallatin Range: 12” of snow totaling 1.2” of SWE.</li>
<li><a href="https://www.mtavalanche.com/weather/stations/fischer-creek">Fisher Creek</a> Snotel site, Cook City: 14” of snow totaling 1.5” of SWE.</li>
<li><a href="https://www.mtavalanche.com/weather/stations/fischer-creek">Carrot Basin</a> Snotel site, southern Madison Range: 9” of snow totaling .9” of SWE.</li>
<li><a href="https://www.mtavalanche.com/weather/yellowstoneclub/timber">Timber weather station</a>, Yellowstone Club: 9” of snow totaling .7” of SWE.</li>
</ul>

<p>The government might be shutting down, but avalanches won’t be. Most avalanches occur during or immediately after a storm and today will be no exception. The main concern will be slides failing in the new snow. Wind slabs, storm slabs, and loose snow avalanches (sluffs) will all be a possibility.</p>

<p>Yesterday, I skied north of Bridger Bowl and got the new snow to move easily in steep terrain (<strong><a href="https://www.youtube.com/watch?v=-ziyDBVHveE">video</a></strong&gt;). Sluffs were moving quickly and entraining large volumes of snow, creating healthy debris piles in runout zones. Bridger Bowl Ski Patrol reported similar results during control work. Skiers in the northern Bridgers also reported touchy conditions, mainly on wind loaded slopes. Although winds calmed with the passing of the storm, fresh wind slabs will remain sensitive near upper elevation ridgelines.</p>

<p>Another problem to look out for will be a layer of surface hoar or near surface facets under the new snow. This layer is not widespread, but was observed on some sheltered slopes prior to the storm (<a href="https://www.mtavalanche.com/images/18/surface-hoar"><strong>photo</stro…;). Look out for this problem when traveling in steep, sheltered terrain.</p>

<p>An additional problem will be slides failing on a layer of facets buried 2-4’ deep. This layer has been getting stronger, but still holds the potential to produce large and dangerous slides (<a href="https://www.mtavalanche.com/images/18/unstable-snow-avalanche-and-colla…;). Keep an eye out for this problem in mid to low elevation terrain where the snowpack is shallower and weaker (<a href="https://www.mtavalanche.com/images/18/dudley-creek"><strong>snowpit</st…;).</p>

<p>Today, human triggered avalanches are likely and the avalanche danger is rated <strong>CONSIDERABLE</strong>.</p>

<p>If you get out and have any avalanche or snowpack observations to share, drop a line via our <a href="https://www.mtavalanche.com/node/add/snow_observation">website</a&gt;, email (<a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a&gt;), phone (406-587-6984), or Instagram (#gnfacobs).</p>

<p>The combination of new snow, wind and buried weak layers will keep the avalanche danger elevated in the Lionhead area near West Yellowstone. Today, there will be multiple avalanche problems to look out for. The main problem will large persistent slab avalanches failing on a layer of facts buried 2-4’ feet deep. This layer has been slow to gain strength and has produced numerous human triggered slides over the past week (<a href="https://youtu.be/taPrFLj52aA"><strong>video</strong></a><strong&gt;, </strong><a href="https://www.mtavalanche.com/images/18/snowmobile-triggered-avalanche-li…;). Today, all steep slopes should be considered suspect and avalanche terrain should be approached with caution.</p>

<p>Additional problems include cornices and wind slabs. Strong winds over the past 24 hours contributed to cornice and wind slab growth near the ridgelines. These will both be touchy to human triggers today. Give cornices a wide berth along the ridgelines and avoid wind loaded slopes in steep, upper elevation terrain.</p>

<p>Today, wind slabs and weak layers make human triggered avalanches likely and the avalanche danger is rated <strong>CONSIDERABLE</strong>.</p>

<p>New snow instabilities will be the main issue in the mountains around Bozeman, Big Sky and Cooke City. Over the past six hours, the Bridger Range has picked up 10” of new snow totaling nearly 1” of SWE. The mountains south of Bozeman have picked up 5-7” totaling .5 to .7” of SWE.</p>

<p>Snow and wind throughout the day will allow wind slabs and storm slabs to grow in size and distribution. Wind loaded slopes will be the most prone to producing human triggered slides (<a href="https://www.mtavalanche.com/photos"><strong>photo</strong></a&gt;). Watch for fresh wind slabs on the leeward side of ridgelines and cross loaded terrain features. Cracking and collapsing of the new snow are obvious clues of instability. Today, wind loaded slopes will fail easily under the weight of a skier or rider and should be approached with caution.</p>

<p>On some slopes, the new snow has been deposited on a layer of surface hoar or near surface facets (<a href="https://www.mtavalanche.com/images/18/surface-hoar"><strong>photo</stro…;, <a href="https://www.youtube.com/watch?v=WyhGoVqCMcc">video</a></strong&gt;). These layers are not widespread, but have survived on some shady and sheltered slopes. This will be something to look out for when traveling in steep, sheltered terrain.</p>

<p>Last but not least, slides still have to the potential to fail on weak facets buried 2-4’ deep. Earlier in the week, skiers west of Cooke City experienced cracking/collapsing and observed a fresh avalanche (<a href="https://www.mtavalanche.com/images/18/unstable-snow-avalanche-and-colla…;). This layer also produced unstable results in stability tests north of Big Sky on Wednesday (<a href="https://www.youtube.com/watch?v=Z5zkCJfIfdI"><strong>video</strong></a&…;, <strong><a href="https://www.mtavalanche.com/images/18/dudley-creek">snowpit</a></strong…;). Although this deep instability is gaining strength, slides failing this layer can’t be entirely ruled out.</p>

<p>Today, human triggered avalanches are likely on wind loaded slopes which have a <strong>CONSIDERABLE</strong> avalanche danger. Non-wind loaded slopes have a <strong>MODERATE</strong> avalanche danger. The danger could rise on all slopes if the storm continues through the day.&nbsp;</p>

<p>If you get out and have any avalanche or snowpack observations to share, drop a line via our <a href="https://www.mtavalanche.com/node/add/snow_observation">website</a&gt;, email (<a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a&gt;), phone (406-587-6984), or Instagram (#gnfacobs).</p>