19-20

<p>In the mountains near West Yellowstone, heavy new snow and strong wind are overloading a very weak snowpack and creating dangerous avalanche conditions. Large avalanches can easily be triggered on a layer of weak, sugary snow at the base of the snowpack (<strong><a href="https://www.mtavalanche.com/images/19/ect-near-two-top">photo</a></stro…;). Avalanches can be triggered on low angle terrain below steep slopes. Natural avalanches are likely on wind-loaded slopes where the biggest slabs of snow will grow through the day. Avoid travel on and underneath steep slopes. Avalanche danger is <strong>HIGH</strong> on wind loaded slopes and <strong>CONSIDERABLE</strong> on all other slopes.</p>

<p>See the <strong><a href="https://www.mtavalanche.com/forecast/lionhead">Lionhead</a></strong&gt; or <strong><a href="https://www.mtavalanche.com/forecast/centennials">Centennials</a></stro…; regional page for videos and photos that show the weak, unstable snowpack there.</p>

<p>The mountains near Big Sky and the Taylor Fork have a weak, sugary layer of facets at the base of the snowpack (<strong><a href="https://www.mtavalanche.com/images/19/unstable-ect-weak-snow-beehive">p…;, <strong><a href="https://www.mtavalanche.com/sites/default/files/styles/very_large_1200w…;, <strong><a href="https://www.youtube.com/watch?v=AbtyS3X7glA&amp;list=PLXu5151nmAvSbcbVf…;). This snow structure is similar to the mountains near West Yellowstone, but half as much new snow is expected near Big Sky and Taylor Fork. Today new snow and strong wind will increase the avalanche danger and make avalanches easy to trigger. Avalanches breaking on sugary, weak snow can be triggered from lower angle terrain below steep slopes. Natural avalanches are possible on wind loaded slopes as they are loaded through today. Avalanche danger is <strong>CONSIDERABLE</strong>.</p>

<p>The mountains near Cooke City have a snowpack that lacks widespread buried weak layers. Avalanches will mostly break directly below the new snow from last night and today, which will total over a foot of snow equal to at least 1” of<strong> <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</a></strong>. Danger will increase through the day, and avalanches will be largest and easy to trigger where strong winds drift new snow into thick slabs. Avoid steep wind-loaded slopes. Practice cautious route finding and conservative terrain selection. Avalanche danger is <strong>CONSIDERABLE</strong>.</p>

<p>In the Bridger Range and Hyalite avalanches will break on the interface below the new snow, mainly where it is drifted into fresh slabs. Expect avalanches to become larger and easier to trigger as snow piles up through today. Carefully assess the stability of the new snow before riding in steep terrain.</p>

<p>On Tuesday and Thursday, Bridger Bowl Ski Patrol triggered hard slab avalanches that broke on a thin layer of facets (<u><strong><a href="https://www.mtavalanche.com/images/19/large-avalanche-mundys-bowl-bridg…;, <u><strong><a href="https://www.youtube.com/watch?v=mbm3kJ652Fk&amp;list=PLXu5151nmAvSbcbVf…;). You can trigger similar slides today on heavily wind-loaded slopes near the ridgeline, such as the upper third of Saddle Peak. Today the avalanche danger is <strong>MODERATE.</strong></p>

<p>If you get out, please send us your observations no matter how brief. You can fill out an&nbsp;<u><strong><a href="https://www.mtavalanche.com/node/add/snow_observation">observation form</a></strong></u>, email us (<u><strong><a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a></strong></u&gt;), leave a VM at 406-587-6984, or Instagram (#gnfacobs).</p>

<p>Weak snow at the ground is widespread near Big Sky and West Yellowstone (<strong><a href="https://www.mtavalanche.com/images/19/ect-near-two-top">photo</a></stro…;). It remains possible to trigger an avalanche where these weak layers have a cohesive slab of newer snow above them. Any slope where you’re not sinking to the ground as you ski or ride deserves further investigation, as that is a good sign that you may have a cohesive enough slab for an avalanche (<strong><a href="https://www.youtube.com/watch?v=AbtyS3X7glA&amp;list=PLXu5151nmAvSbcbVf…;, <strong><a href="https://www.youtube.com/watch?v=tlOyL-hbwE4&amp;list=PLXu5151nmAvSbcbVf…;, <strong><a href="https://www.youtube.com/watch?v=mAbxNKrJb2U&amp;list=PLXu5151nmAvSbcbVf…;). A quick <a href="https://www.youtube.com/watch?v=6s9LND3-gho">Extended Column Test</a> is a great way to check that slab-weak layer combination and search for signs of instability.</p>

<p>Avalanches are possible and the avalanche danger is <strong>MODERATE</strong> today.</p>

<p>Triggering avalanches on weak snow near the ground is also possible in the Bridger Range. However, these concerns are more localized to heavily wind loaded slopes near the ridgeline. On Tuesday and Thursday, Bridger Bowl Ski Patrol triggered large avalanches that broke on a thin layer of weak snow low in the snowpack (<strong><a href="https://www.mtavalanche.com/images/19/large-avalanche-mundys-bowl-bridg…;, <strong><a href="https://www.youtube.com/watch?v=mbm3kJ652Fk&amp;list=PLXu5151nmAvSbcbVf…;). Alex and Dave also found this weak layer and got unstable test results on it near the Throne earlier in the week (<strong><a href="https://www.youtube.com/watch?v=5U2vv30wHmw&amp;list=PLXu5151nmAvSbcbVf…;). You can trigger similar slides today on high elevation slopes with thick drifts of windloaded snow. With these hard slabs, avoiding suspect slopes is your best strategy.</p>

<p>The avalanche danger is <strong>MODERATE </strong>on windloaded slopes. Elsewhere, the avalanche danger is <strong>LOW</strong>.</p>

<p>The Northern Gallatin Range and mountains around Cooke City have the deepest snowpacks and the most isolated weak layers. Triggering an avalanche is unlikely. However, we can’t rule out the possiblity that there may pockets with lingering instabilities. Dig a quick pit to look for unstable weak layers before committing to a steep slope. The avalanche danger is <strong>LOW</strong>.</p>

<p>If you get out, please send us your observations no matter how brief. You can fill out an&nbsp;<strong><a href="https://www.mtavalanche.com/node/add/snow_observation">observation form</a></strong>, email us (<strong><a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a></strong&gt;), leave a VM at 406-587-6984, or Instagram (#gnfacobs).</p>

<p>The snowpack in the Madison Range, Southern Gallatin Range, and Lionhead area has a weak foundation of sugary, faceted snow (<strong><a href="https://www.mtavalanche.com/images/19/poor-snow-structure-buck-ridge">p…;, <strong><a href="https://www.youtube.com/watch?v=AbtyS3X7glA&amp;list=PLXu5151nmAvSbcbVf…;, <strong><a href="https://www.youtube.com/watch?v=tlOyL-hbwE4&amp;list=PLXu5151nmAvSbcbVf…;, <strong><a href="https://www.youtube.com/watch?v=mAbxNKrJb2U&amp;list=PLXu5151nmAvSbcbVf…;). As each additional day passes since the last snowfall, avalanches are slowly becoming less likely. However, triggering an avalanche remains possible on slopes with a cohesive slab capping the weak snow at the ground. Before getting onto a steep slope quickly dig down to see if you have this worrisome combination of slab and weak layer. If you find this combo, evaluate it carefully or stick to lower angled terrain.</p>

<p>The avalanche danger is <strong>MODERATE</strong> today.</p>

<p>Triggering avalanches remains possible on heavily wind loaded slopes in the Bridger Range, Northern Gallatin Range and around Cooke City. Yesterday, Bridger Bowl Ski Patrol triggered several large avalanches breaking under hard slabs of wind drifted snow near the ridgeline. Alex went up to take a look at these slides and found they were breaking on a thin layer of weak snow low in the snowpack (<strong><a href="https://www.youtube.com/watch?v=mbm3kJ652Fk&amp;list=PLXu5151nmAvSbcbVf…;). You can trigger similar slides today on high elevation slopes with thick drifts of windloaded snow (e.g. Saddle Peak). Hard slabs are a difficult problem to manage, you will likely not see any signs of instability until you hit just the wrong spot and trigger a large slide.</p>

<p>Slopes without thick winddrifts are generally stable. However, digging to evaluate the snowpack for yourself on a particular slope is the best way to avoid an unpleasant surprise. &nbsp;</p>

<p>Today, avalanches are possible on wind loaded slopes where avalanche danger is <strong>MODERATE</strong>. On non-wind loaded slopes avalanche danger is <strong>LOW</strong>.</p>

<p>If you get out, please send us your observations no matter how brief. You can fill out an&nbsp;<strong><a href="https://www.mtavalanche.com/node/add/snow_observation">observation form</a></strong>, email us (<strong><a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a></strong&gt;), leave a VM at 406-587-6984, or Instagram (#gnfacobs).</p>