17-18

<p>The Lionhead area near West Yellowstone has a weak, unstable snowpack and large avalanches are easy to trigger (<a href="https://www.mtavalanche.com/images/18/poor-snowpack-structure-lionhead"…;). This weak snowpack was loaded with 2 feet of snow equal to 2.5” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</a> (SWE) last week, and it will not quickly gain strength. Yesterday at Lionhead, a group of snowmobilers triggered a 2-4’ deep avalanche from within trees low on the slope (<strong><a href="https://www.mtavalanche.com/images/18/remote-triggered-slide-near-lionh…;). Eric was at Hebgen Lake and had large collapses while touring through the trees. He found a snowpack similar to Lionhead, capable of producing avalanches across entire slopes (<strong><a href="https://youtu.be/taPrFLj52aA">video</a></strong&gt;). This is bullseye information to avoid travel on and below steep slopes. Avalanche danger is <strong>CONSIDERABLE</strong>.</p>

<p>The Bridger Range got 3-4 feet of snow equal to 3.7” SWE since Wednesday. On Friday, Eric and I found short-lived new snow instabilities to be our main concern (<a href="https://youtu.be/Nxyxl-apgAM"><strong>video</strong></a&gt;). Strong wind last night drifted snow into slabs 2-3’ feet thick that are easy to trigger. These slabs are most likely near ridgelines, and possible at lower elevations near the edges of cliffs and steep, convex rolls. Aside from wind slabs, the snowpack in the Bridger Range is generally strong. However, almost 4” of water in four days is like a widespread stability test. Give steep slopes a day to pass the exam and adjust to the recent load. Avalanche danger today is <strong>CONSIDERABLE</strong>.</p>

<p>In Cooke City and the southern Madison and Gallatin ranges avalanches breaking on a weak layer of facets 3-4’ deep are getting harder to trigger, but recent observations show they are possible. A large natural avalanche was observed on the Fin near Cooke City on Friday (<strong><a href="https://www.mtavalanche.com/images/18/fin-avalanche-crown-close">photo<…;). Before the recent 2-3’ of snow, riders in the southern Madison Range had unstable stability test scores (<strong><a href="https://www.mtavalanche.com/images/18/instability-teepee-basin">photo</…;). Doug had similar findings at Bacon Rind on Thursday (<a href="https://www.youtube.com/watch?v=gK10ZVPy7Wk&amp;list=PLXu5151nmAvQSYtIf…;). In addition, wind has drifted snow into small wind slabs near ridgelines that are easy to trigger today. Avalanche danger is <strong>CONSIDERABLE</strong> today.</p>

<p>In the mountains near Hyalite and Big Sky moderate winds drifted recent new snow into slabs that are possible to trigger. Yesterday, Doug found fresh drifts easy to trigger near ice climbs in Hyalite (<strong><a href="https://youtu.be/D_yPQDu0REg">video</a></strong&gt;), and skiers near Divide Peak saw a natural avalanche on a wind loaded slope (<strong><a href="https://www.mtavalanche.com/images/18/natural-wind-slab-hyalite">photo<…;). These slabs will gain strength, but be cautious of wind loaded slopes today.</p>

<p>Avalanches on weak facets 2-4’ deep are possible, but confined to specific terrain where the snowpack is relatively shallow, 3-5’ deep. On Friday, skiers in the northern Madison Range remotely triggered a large avalanche on this layer (<a href="https://www.mtavalanche.com/images/18/skier-triggered-slide-dudley-cree…;). Be cautious of lower elevation terrain and slopes with highly variable snow depth. Today, the avalanche danger is rated <strong>MODERATE</strong> on all slopes.</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 Bridger Range has a foot of new snow equal to 1.4” of snow water equivalent (SWE) since yesterday morning, and 2.5 feet of snow equal to 3” of SWE since Wednesday morning. Eric and I were in the northern Bridgers yesterday and found an overall strong snowpack with new snow instabilities our main concern (<strong><a href="https://youtu.be/Nxyxl-apgAM">video</a></strong&gt;). The rapid, heavy load of snow since yesterday will increase the size and likelihood of avalanches today. Moderate wind overnight drifted new snow into slabs near ridgelines that will be easy to trigger or break naturally. Despite a fairly strong snowpack, the heavy cumulative load since Wednesday makes avalanches breaking on facets buried 3-4’ deep more likely. Avoid wind loaded slopes and be extra cautious of all steep terrain today. The avalanche danger is <strong>HIGH</strong> on wind loaded slopes and <strong>CONSIDERABLE</strong> on non-wind loaded slopes.</p>

<p>The Lionhead area near West Yellowstone has an unstable snowpack, and 2 feet of snow this week equal to 2.4” of snow water equivalent (SWE) created very dangerous avalanche conditions (<a href="https://youtu.be/e9OACzfb7pQ"><strong>video</strong></a&gt;, <a href="https://www.mtavalanche.com/images/18/poor-snowpack-structure-lionhead"…;). Yesterday’s avalanche warning is no longer in effect, but large avalanches are easy to trigger and can be triggered from flat or low angle terrain below steep slopes. Avoid travel on and underneath steep slopes. Today, large avalanches are easy to trigger and natural avalanches are possible. The avalanche danger is <strong>CONSIDERABLE</strong>.</p>

<p>The southern Madison and Gallatin Ranges and mountains near Cooke City got to 2-2.5 feet of snow equal to 2-2.5” of SWE since Wednesday. The snowpack in these areas is handling this load well, as Doug found in Bacon Rind on Thursday (<a href="https://www.youtube.com/watch?v=gK10ZVPy7Wk&amp;list=PLXu5151nmAvQSYtIf…;). However, more snow equals more avalanches, and this recent snow was no exception. Yesterday, a large natural avalanche was observed on the Fin near Cooke City (<strong><a href="https://www.mtavalanche.com/images/18/natural-avalanches-fin">photo</a>…;), and skiers reported collapsing on lower elevation terrain. A layer of facets buried 2-4’ deep is stronger than it was a few weeks ago, but avalanches on this layer are&nbsp;easier to trigger&nbsp;with the weight of the recent snow. New snow, wind and&nbsp;natural avalanches mean avalanches are easy to trigger, and the avalanche danger today is <strong>CONSIDERABLE</strong>.</p>

<p>The mountains near Hyalite and Big Sky have had less snow than elsewhere, and have a generally stronger snowpack. Moderate westerly winds drifted recent new snow into wind slabs that are easy to trigger near ridgelines today. There’s still the possibility for slides to break on facets buried 2-4’ deep. Skiers in Dudley Creek in the northern Madison Range remotely triggered a large avalanche yesterday (<strong><a href="https://www.mtavalanche.com/images/18/skier-triggered-slide-dudley-cree…;). This instability is confined to specific terrain (where the snowpack is relatively shallow, 3-5’ deep), and needs to be watched for when traveling on mid to low elevation&nbsp;slopes or areas where the snowpack depth is highly variable. Today, the avalanche danger is rated <strong>CONSIDERABLE</strong> on wind loaded slopes and <strong>MODERATE</strong> on non-wind loaded slopes.</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>