17-18

<p>The mountains near West Yellowstone will see the strongest impacts of this current storm system. New snow and wind will form a fresh batch of wind slabs, which will grow in size and distribution throughout the day. Instability will be on the rise, so evaluate terrain and the snowpack carefully before exposing yourself to steeper slopes. The safest riding today will be on sheltered, low angle slopes not attached to steeper slopes.</p>

<p>Dry loose avalanches (sluffs) will also be possible in steeper terrain. This will be a growing problem as snow accumulates through the day. These slides won’t be huge, but could potentially carry a skier or rider into trees, rocks or gullies. Give cornices a wide berth along the ridgelines as they can break further back than you might expect.</p>

<p>Outside of new snow instabilities, the snowpack is mostly stable.</p>

<p>Today, the combination of new snow and wind will make human triggered avalanches likely on wind loaded slopes which have a <strong>CONSIDERABLE</strong> avalanche danger. Non-wind loaded slopes have a <strong>MODERATE</strong> avalanche danger.</p>

<p>The mountains saw fresh snow and wind earlier this week. This created dense slabs sitting on top of lower density snow. On Wednesday, these fresh slabs were reactive to stability tests in the Bridger range (<a href="https://www.youtube.com/watch?v=pL3sFBfPucM&amp;t=0s&amp;list=PLXu5151n…;). These slabs will be largest and most widespread at upper elevations and in cross loaded terrain, and may be covered by fresh snow throughout the course of the day. These slabs have had a few days to and stabilize, but they could still be triggered (<a href="https://www.youtube.com/watch?v=Uyy9N7OmpEs&amp;index=3&amp;list=PLXu51…;

<p>Growing cornices continue to pose a threat and should be given a wide berth. They can break farther back than expected if you hit the right spot. A large natural slide occurred on Monday in the Bridger range (<a href="https://www.mtavalanche.com/images/18/large-natural-slide-northern-brid…;), likely due to cornice failure.</p>

<p>Today, natural avalanches are unlikely, but human triggered avalanches remain possible on wind loaded slopes which have a <strong>MODERATE</strong> avalanche danger. Non-wind loaded slopes have a <strong>LOW </strong>avalanche danger.</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 snowpack across the advisory area is well over 100% (<strong><a href="https://www.mtavalanche.com/images/18/snowpack-swe-normal">photo</a></s…;), which is creating deep and mostly stable conditions (<strong><a href="https://www.mtavalanche.com/images/18/how-deep-cooke-city-deep">photo</…;). The one exception is wind loaded slopes (<strong><a href="https://www.youtube.com/watch?v=Uyy9N7OmpEs&amp;index=3&amp;list=PLXu51…;). Over the past few days, strong winds have transported an abundance of low density snow into thick slabs (<strong><a href="https://www.mtavalanche.com/photos">photo</a></strong&gt;). These slabs mostly exist in wind loaded terrain near ridgelines and cross loaded sub-ridges.</p>

<p>Yesterday, we rode into the northern Bridgers and observed strong winds transporting snow. This was creating fresh slabs that were reactive in stability tests (<strong><a href="https://www.youtube.com/watch?v=pL3sFBfPucM&amp;t=0s&amp;list=PLXu5151n…;). We also checked out a large slide that occurred on Monday (<a href="https://www.mtavalanche.com/images/18/large-natural-slide-northern-brid…;). This slide appears to have been triggered by a falling cornice. Cornices are massive right now and pose a significant threat. Yesterday, skiers near Big Sky tried cutting a small chunk of cornice, but ended up triggering a much larger piece, which caught them by surprise. Make sure and give these monsters extra distance along the ridgelines and limit exposure time on slopes below.</p>

<p>Winds will remain moderate to strong today which will continue to build cornices and wind slabs. Recognize and avoid wind loaded slopes, especially in steep high consequence terrain.</p>

<p>Outside of wind loaded slopes there a few isolated instabilities to keep an eye out for. A thin layer of facets 2-3’ feet deep have produced unstable results in a few stability tests. On a positive note, this layer has not produced recent avalanches and has a very isolated distribution. While it’s not a major concern, it’s something to keep in mind.</p>

<p>Today, human triggered avalanches are possible on wind loaded slopes which have a <strong>MODERATE</strong> avalanche danger. Non-wind loaded slopes have a <strong>LOW</strong> avalanche danger.</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>Yesterday morning the Bridger Range had 22” of powder with strong winds. This combination created avalanches, both natural and human triggered. I toured along the ridge, north of Bridger Bowl, and got shooting cracks in the wind slabs (<strong><a href="https://youtu.be/Uyy9N7OmpEs">video</a&gt;, <a href="https://www.mtavalanche.com/images/18/wind-slabs-cracking">photo</a></s…;); other skiers ventured into Wolverine Bowl and triggered a slide (<strong><a href="https://www.mtavalanche.com/images/18/skier-triggered-avalanche-wolveri…;); a snowboarder triggered a small wind pocket south of the ski area (<strong><a href="https://youtu.be/f33fhTh5Oms">video</a></strong&gt;); a small natural avalanche broke on Saddle Peak (<strong><a href="https://www.mtavalanche.com/images/18/natural-avalanche-saddle-peak">ph…;); and a large natural avalanche was seen near Fairy Lake (<strong><a href="https://www.mtavalanche.com/images/18/natural-avalanche-near-fairy-lake…;).</p>

<p>Winds have decreased and so will avalanche activity. I’m more concerned about someone getting caught in a slide today than yesterday because the red flags of shooting cracks, wind-loading and natural avalanches may be absent. It has been less than 24-hours since the winds lessened and wind slabs may still be unstable. Today the avalanche danger is a solid <strong>MODERATE</strong> on all wind-loaded terrain and<strong> LOW</strong> elsewhere.</p>

<p>Since Saturday, Cooke City has gotten 1.5-2 feet of snow. The only avalanches were point release, loose snow avalanches; nothing deeper. Ski guides reported windy conditions yesterday and had small wind slabs crack under their skis. Seven days ago Eric found a weak layer of faceted snow 2-3 feet deep (<strong><a href="https://youtu.be/yu1AnPdOjaI">video</a></strong&gt;), but it has not been active. This is good news, but I’m still reluctant to give non-wind-loaded slopes the bright green light. Partially it has to do with this layer, but the other part is that I’m gun shy because my confidence in the snowpack isn’t as solid as the other mountain ranges. For today, the avalanche danger is rated <strong>MODERATE</strong> on all slopes.</p>

<p>The Gallatin and Madison Ranges and the Lionhead area received 1-2 feet of snow since Saturday night along with wind. I rode into Lionhead on Sunday (<strong><a href="https://youtu.be/FqzP2G2hpcM">video</a></strong&gt;) and my concerns were limited to wind-loaded slopes. On all other slopes the snowpack is generally stable which Eric described in his <strong><a href="https://youtu.be/aqz9MPBYfyo">video</a></strong&gt; from Friday. The evidence for stability has been stacking up with concurring observations from Hyalite, around Big Sky, and in the southern Madison Range. There are no widespread weak layers in the snowpack. For today, the avalanche danger is <strong>MODERATE</strong> on wind-loaded slopes and <strong>LOW </strong>everywhere else.</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>