18-19

<p>The snowpack in the northern Madison Range requires scrutiny. On Saturday in Bear Basin, skiers triggered a large avalanche on weak snow near the ground (<a href="https://www.mtavalanche.com/node/20359">details and photos</a>). It released in a rocky, shallow area of the snowpack and propagated under thicker wind slabs. It is ugly terrain and luckily no one was caught. Triggering a large slide like this is getting more difficult without new snow loading, but still makes my palms sweat.</p>

<p>Dig and look for instability; it only takes a few minutes. A deep slab breaking in a test leaves a strong impression, but conversely, <em>not</em> finding instability is not a green light. Be careful around shallow areas of the snowpack, especially in rocky terrain where facets can be well developed, because these are likely trigger zones. For today avalanches remain possible and the danger is rated MODERATE.</p>

<p>The snowpack in the rest of the forecast area is generally safe with a few isolated issues. A weak layer of faceted snow was buried 8-16” under the snow surface last week, but it is not a widespread problem. Alex found it to be spotty in Hyalite (<strong><a href="https://www.youtube.com/watch?v=7YtcaZzw5MQ&amp;index=5&amp;list=PLXu51…;), Ian could not get this layer to fracture above Hebgen Lake (<u><strong><a href="https://www.youtube.com/watch?v=TCn1ZXThYzM&amp;list=PLXu5151nmAvRNl9ku…;), and near Cooke City they strengthened over the weekend (<u><strong><a href="https://www.youtube.com/watch?v=P4oCbQ5oIHU&amp;index=2&amp;list=PLXu51…;). This layer is close to the surface and easy to test.</p>

<p>On Monday, skiers were able to trigger thin wind drifts (6”) in the northern Bridger Range (<u><strong><a href="https://www.mtavalanche.com/node/20370">details</a></strong></u&gt;, <u><strong><a href="https://www.mtavalanche.com/images/19/wind-slab-fairy-lake">photo</a></…;). This problem is not widespread, but small avalanches could push us over cliffs or into terrain traps.</p>

<p>Eric skied into the southern Gallatin Range yesterday and found a relatively thin snowpack with sugary facets at the ground (<strong><a href="https://www.youtube.com/watch?v=CqDjipxrGwM&amp;list=PLXu5151nmAvRNl9ku…;). In general stability was good and getting better with time. An avalanche on Sunday in Paradise Valley (outside our forecast area) failed in a snowpack that looks similar to this (<u><strong><a href="https://www.mtavalanche.com/node/20360">details</a></strong></u&gt;, <u><strong><a href="https://www.mtavalanche.com/images/19/avalanche-knowles">photo</a></str…;). It was skier triggered and broke near the ground wiping out tracks from the day before. Triggering a slide like this is unlikely, but not impossible.</p>

<p>For today, the avalanche danger is rated LOW. Before jumping into steep terrain do a quick stability test since it may reveal one of these isolated problems. If you take your sport seriously, then be serious and dig. People still die during a low avalanche danger.</p>

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

<p>It remains possible to trigger large avalanches near Big Sky. Slides may break on weak layers buried last week (8-16” deep) or on weak snow near the ground. On Saturday, a skier in Bear Basin triggered a slide that broke 3-12 feet deep (<strong><a href="https://www.mtavalanche.com/node/20359">details and photos</a></strong><strong>)</strong>. It initially broke on a weak layer in the upper snowpack and then stepped down to weak snow at the ground. This slide was triggered from a shallow spot near rocks on a steep, windloaded, slope with variable snow depth (<strong><a href="https://www.mtavalanche.com/images/19/deep-slab-bear-basin-2">photo</a>…;). Recent avalanche activity is a clear sign that some slopes remain unstable.</p>

<p>Yesterday, skiers in Middle Basin got unstable tests results on the shallowly buried facet layer and decided to back off from their initial objective, sticking to lower angled terrain. This is a great example of searching for signs of instability, and then adjusting plans according.</p>

<p>Stack the deck in your favor by choosing uniform, non-windloaded slopes and digging down to look for and assess the weak layers in the upper snowpack. These weak layers have gained strength, and do not exist on all slopes, but you want to make sure you haven’t stumbled onto a slope where they remain unstable (<strong><a href="https://www.youtube.com/watch?v=7YtcaZzw5MQ&amp;list=PLXu5151nmAvRNl9ku…;, <strong><a href="https://www.mtavalanche.com/images/19/throne-stable-snowpit-9-mar">phot…;).</p>

<p>Triggering an avalanche is possible and the avalanche danger is <strong>MODERATE</strong>.</p>

<p>Triggering an avalanche has become unlikely in the rest of the advisory area. Doug dug on five different slopes yesterday near Cooke City looking for unstable facets in the upper snowpack (8-16” deep) and didn’t find them (<strong><a href="https://www.youtube.com/watch?v=P4oCbQ5oIHU&amp;index=2&amp;list=PLXu51…;). On Sunday, I found them near Hebgen Lake, but they weren’t unstable (<strong><a href="https://www.youtube.com/watch?v=TCn1ZXThYzM&amp;list=PLXu5151nmAvRNl9ku…;). Still, last week avalanches broke on this layer in Hyalite (<strong><a href="https://www.mtavalanche.com/images/19/skier-triggered-mt-blackmore">pho…;) and near Cooke City (<strong><a href="https://www.mtavalanche.com/node/20333">details</a></strong&gt;), so it’s worth quickly checking for this layer before getting onto a steep slope.</p>

<p>While the probability of triggering a slide has decreased, the potential consequences have not. We can’t completely rule out avalanches breaking at the base of the snowpack. On Sunday, skiers in the Absarokas (outside of the advisory area) triggered a deep slab avalanche on a slope with numerous tracks (<strong><a href="https://www.mtavalanche.com/node/20360">details</a></strong&gt;, <strong><a href="https://www.mtavalanche.com/images/19/avalanche-knowles">photo</a></str…;).</p>

<p>Yesterday in the Northern Bridgers two separate groups of skiers triggered thin wind slab avalanches (<strong><a href="https://www.mtavalanche.com/node/20370">details</a></strong&gt;, <strong><a href="https://www.mtavalanche.com/images/19/skier-triggered-wind-slab-n-bridg…;). These slides only broke 6” deep and didn’t generate much debris, but be mindful in places where a slide knocking you off your feet would have big consequences. Also watch out for small wet loose avalanches on steep sunny slopes as the snow surface heats up.</p>

<p>Avalanches are unlikely and the avalanche danger is <strong>LOW</strong> today.</p>

<p>If you get out and have any avalanche or snowpack observations to share, contact us 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>