17-18

<p>The equation is pretty simple around Cooke City. Heavy snow and strong winds are creating very dangerous avalanche conditions. Over the past 24 hours more than a foot of snow has fallen totaling 1.1” of SWE. This heavy shot of snow was accompanied by strong winds out of the west. Today, I expect natural and human triggered avalanches to occur on wind loaded slopes. Avoid all wind loaded terrain and be extra cautious when traveling in avalanche run out zones (<a href="https://www.youtube.com/watch?v=cj2Qhn1ldQA&amp;list=PLXu5151nmAvQSYtIf…;

<p>Non-wind loaded slopes also pose a significant avalanche threat. Storm slabs will be easy to trigger in steeper terrain. Yesterday, Alex skied up Republic Creek south of town and found steep, non-wind loaded slopes to be touchy to human triggers. I expect steep slopes to be even more reactive today. Slides have the potential to step down to buried surface hoar 2-3’ deep or weaker layers near the ground (<a href="https://www.mtavalanche.com/images/18/natural-avalanche-woody-ridge"><s…;, <a href="https://www.mtavalanche.com/images/18/propagation-surface-hoar-near-coo…;).&nbsp;Today's a great day to&nbsp;seek out lower angle terrain while practicing cautious route-finding and conservative decision making.</p>

<p>Today, very dangerous avalanche conditions exist on wind loaded slopes which have a <strong>HIGH</strong> avalanche danger. Non-wind loaded slopes have a <strong>CONSIDERABLE</strong> avalanche danger.</p>

<p>Today, wind loaded slopes are the main concern in the mountains around West Yellowstone. Four to six inches of new snow over the past few days combined with moderate to strong winds out of the west will create a fresh batch of wind slabs (<a href="https://www.mtavalanche.com/images/18/small-avalanche-lionhead"><strong…;). Watch for wind loaded slopes below ridgelines and on the leeward side of cross-loaded terrain features.</p>

<p>Buried surface hoar continues to produce unstable test results and is the main layer of concern. This pesky weak layer does not exist on all slopes so digging a pit and doing a quick stability test is an easy way to stack the deck in your favor. (<a href="https://youtu.be/thn9hnFUi4Y"><strong>video</strong></a><strong&gt;, </strong><a href="https://www.mtavalanche.com/photos"><strong>photo</strong></a&gt;). Facets near the ground are getting stronger, but still hold the potential to produce large slides in isolated areas.</p>

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

<p>Yesterday's fast moving storm dropped 6” inches of snow in the Bridgers and 3-5” around Hyalite and Big Sky. The new snow was easily transported by strong westerly winds. Yesterday, both Big Sky and Bridger Bowl Ski Patrols found wind loaded slopes to be reactive during control work. Slides are staying confined to the new snow, but have enough volume to carry and potentially bury a skier or rider. Warm temps will make wind slabs a little stubborn, but they still can’t be trusted, especially in steep high consequence terrain (think Saddle Peak). The snowpack is mostly stable on non-wind loaded slopes (<a href="https://www.youtube.com/watch?v=-Kh4wvvQ3Wk"><strong>video</strong></a>…;

<p>Today, the avalanche danger is rated <strong>MODERATE</strong> on all wind-loaded slopes and <strong>LOW</strong> elsewhere. The avalanche danger could rise if this evening’s storm arrives earlier than forecasted.</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 primary avalanche problem in the mountains around Cooke City is wind loaded slopes. New snow combined with moderate winds from the west is the perfect recipe for wind slab formation. Yesterday, Alex rode north of town and observed evidence of a large recent avalanche that occurred in wind loaded terrain (<strong><a href="https://www.youtube.com/watch?v=cj2Qhn1ldQA&amp;list=PLXu5151nmAvQSYtIf…;). This is consistent with another large avalanche that occurred off Woody Ridge earlier in the week (<a href="https://www.mtavalanche.com/images/18/natural-avalanche-woody-ridge"><s…;). Today, staying off wind loaded slopes will be the best way to avoid avalanches (<strong><a href="https://www.mtavalanche.com/images/18/examples-wind-loaded-terrain">pho…;).</p>

<p>A secondary concern is a layer of surface hoar buried 1-2’ deep (<strong><a href="https://www.mtavalanche.com/images/18/propagation-surface-hoar-near-coo…;). Yesterday, Alex got unstable results on this layer in his stability tests. Buried surface hoar is notorious for having sporadic distribution so keep a watchful eye out for this layer before jumping into steeper terrain.</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 <strong>MODERATE</strong> avalanche danger.</p>

<p>Read a recent blog post on the complexities of the snowpack around Cooke City: <a href="https://www.mtavalanche.com/blog/additional-thoughts-regarding-my-uncer…;

<p>Yesterday, snowmobilers triggered a small slide in the Lionhead area near West Yellowstone (<strong><a href="https://www.mtavalanche.com/images/18/small-avalanche-lionhead">photo</…;). Although this side was small and relatively harmless, it’s a key indicator that larger slides are possible. Today, wind loaded slopes are the main concern. Watch for and avoid slopes that appear to be heavily wind load and steer clear of large cornices along the ridgelines. Cornices can break farther back than expected and also trigger larger avalanches on the slopes below.</p>

<p>Additionally, surface hoar buried 1-2’ deep and facets near the ground both hold the potential to produce slides. Buried surface hoar continues to produce unstable test results and is the main layer of concern. Fortunately, this layer is not buried very deep and is easy to look for and assess (<a href="https://youtu.be/thn9hnFUi4Y"><strong>video</strong></a><strong&gt;, <a href="https://www.mtavalanche.com/photos">photo</a></strong&gt;). Facets near the ground are getting stronger, but could still produce large slides in isolated areas.</p>

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

<p>Overnight, winds blew 15-30 mph out of the west. Wind slabs 1-2’ deep likely formed in upper elevation, leeward terrain (<a href="https://www.youtube.com/watch?v=-Kh4wvvQ3Wk"><strong>video</strong></a&…;). These slabs could fail under the weight of a skier or rider. In most cases wind slabs are easy to recognize and avoid, but occasionally catch skiers and riders off guard. It’s poor practice to ski or ride onto a slope to try and intentionally trigger wind slabs. These can break deeper and wider than you might expect and can also break above you. Earlier this winter, a skier in the Bridgers took a nasty ride when he attempted to trigger a wind slab that broke above him and carried him 800’ downslope. Fortunately, he was not injured. Outside of wind loaded slopes, the snowpack is mostly stable.</p>

<p>For today, the avalanche danger is rated <strong>MODERATE</strong> on all wind-loaded slopes and <strong>LOW</strong> elsewhere. The avalanche danger could rise if the storm intensifies throughout the day.</p>