19-20

<p>In December we warned you that we were going to be talking about the weak snow near the ground for a long time. Yesterday, a rider was side hilling across the top of a break over in Buck Ridge and triggered a deep avalanche on this layer (<a href="https://www.mtavalanche.com/node/22129"><strong>avalanche activity</strong></a>). Deep slides continue to occur across our advisory area and where there aren’t happening, well, Doug was unwilling to ski the avalanche terrain on Mount Ellis yesterday even after getting stable test results (<a href="https://www.youtube.com/watch?v=3zzAAW7wFzk"><strong>video</strong></a>…;

<p>Avalanches over the weekend demonstrated instabilities in the northern ranges. Friday, skiers came across a cornice triggered avalanche that propagate 200’ across the slope and failed 2-5’ deep in Bear Basin (<a href="https://www.mtavalanche.com/node/22058"><strong>description and photos</strong></a>) and a natural avalanche that propagated a mile wide in the Divide Peak Basin (<a href="https://www.mtavalanche.com/node/22057"><strong>photos</strong></a&gt;). Saturday, skiers observed many natural avalanches from Mount Blackmore ranging from small to 8’ deep (<a href="https://www.mtavalanche.com/node/22096"><strong>details and photos</strong></a>). Sunday, a natural avalanche broke deep north of Bridger Bowl in Wolverine Bowl (<a href="https://www.mtavalanche.com/node/22103"><strong>details</strong></a&gt;). Yesterday’s lightweight snow (0.3” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</a>) will not significantly change the avalanche danger, but stay vigilant because the snowpack hasn’t gotten a rest yet.</p>

<p>In the southern ranges, a snow biker in the Taylor Fork triggered a 5’ deep slide on Saturday and in the Hayden Creek drainage south of Cooke City a cornice fall triggered an avalanche that failed at the ground (<a href="https://www.mtavalanche.com/images/20/snowmobiler-triggered-slide-taylo… Fork details</strong></a><strong>, </strong><a href="https://www.mtavalanche.com/node/22118"><strong>Hayden Creek details</strong></a>). I spent the last two days in Cooke City and found a stabilizing snowpack, but one that isn’t completely trustworthy yet. There it will take a significant trigger (i.e. a cornice fall or an avalanche in the new snow), a big storm adding a lot of weight, or some bad luck to trigger the weak snow near the ground now insulated by a deep snowpack. New snow is bonding well to the surface, but, where wind had drifted snow, shooting cracks under our skis and sleds demonstrated isolated instabilities (<a href="https://youtu.be/kzAyDyTQsgs"><strong>video</strong></a&gt;). Doug echoed this message in Lionhead, you can still find thinner or wind loaded spots to trigger an avalanche, but it is getting harder (<a href="https://youtu.be/S_gUqe5axGQ"><strong>video</strong></a&gt;).</p>

<p>Today, be cautious in areas that received more new snow and maintain a healthy distrust of the weak snow near the ground. It is still possible to trigger deep and destructive avalanches on the sugary snow as yesterday’s slide in Buck Ridge demonstrates. The avalanche danger is rated MODERATE.&nbsp;</p>

<p>If you get out, please send us your observations no matter how brief. You can fill out an&nbsp;<a href="https://mtavalanche.us17.list-manage.com/track/click?u=6653a830e4819c9e…; target="_blank"><strong>observation form</strong></a>, email us (<a href="mailto:mtavalanche@gmail.com&quot; target="_blank"><strong>mtavalanche@gmail.com</strong></a>), leave a VM at 406-587-6984, or Instagram (#gnfacobs).</p>

<p>In the northern mountains there has been a lot of natural avalanche activity. Most slides broke Friday and Saturday. Many were large, deep and broke trees. Our <strong><a href="https://www.mtavalanche.com/photos">Photos page</a></strong> and <strong><a href="https://www.mtavalanche.com/avalanche-activity">Avalanche Activity page</a></strong> are bursting at the seams with avalanches. Some notable ones:</p>

<ul>
<li>A huge avalanche in <strong><a href="https://www.mtavalanche.com/node/22057">Divide Basin</a></strong>,</li>
<li>Many avalanches on and around <strong><a href="https://www.mtavalanche.com/node/22096">Mt. Blackmore, Elephant Mountain and Alex Lowe Peak</a></strong>,</li>
<li>A large avalanche in <strong><a href="https://www.mtavalanche.com/node/22058">Bear Basin</a></strong>,</li>
<li>An avalanche yesterday morning in <strong><a href="https://www.mtavalanche.com/node/22103">Wolverine Bowl</a></strong>, north of Bridger Bowl.</li>
</ul>

<p>Most of the avalanches were on heavily wind-loaded terrain, but not all. Some were triggered by cornice falls, and the larger slides broke at the ground on the sugary facets that formed in November. What is astonishing is how these slopes did not go with the big storm a week ago, and instead broke with just a few more inches of snow and wind. Like the proverbial ‘straw that broke the camel’s back’ we just witnessed how every snowpack has its breaking point. &nbsp;</p>

<p>Natural activity will become more unlikely today, but triggering slides remains very real. Terrain that folks might normally think of as “safe” are questionable, especially low elevation hills. These have a thin snowpack consisting of very weak snow now capped with a couple feet of snow. Avalanches on <strong><a href="https://www.mtavalanche.com/node/22088">Chestnut Mountain</a></strong>, near <strong><a href="https://www.mtavalanche.com/node/22071">Lick Creek</a></strong>, and <strong><a href="https://www.mtavalanche.com/node/22082">Wheeler Mountain</a></strong> are evidence that slopes near History Rock, Mt Ellis, Beehive Basin and other low lying areas are untrustworthy. The one word avalanche danger, Moderate or Considerable, does not capture the overall seriousness of traveling in avalanche terrain.</p>

<p>Avoid wind-loaded slopes. Avoid steep slopes in general, because after this many avalanches it’s hard to justify. Time will calm things down, but today remains heads-up. On any slope with a wind-load, triggering avalanches is likely and the danger is rated CONSIDERABLE. On all others, triggering avalanches remains possible and the danger is rated MODERATE.</p>

<p>In the southern mountains, including West Yellowstone and Cooke City, there has been new snow and wind most of the last 7 days. A snow biker on Saturday triggered an avalanche in Taylor Fork (<strong><a href="https://www.mtavalanche.com/images/20/snowmobiler-triggered-slide-taylo…;), and a large avalanche on the east face of Woody Ridge, south of Cooke City, avalanched on Friday. Dave is in Cooke City. His concerns are two-fold: winds have drifted snow that could avalanche, and weak, sugary snow at the ground still has the potential to slide. He could feel the unconsolidated snow at the ground when he probed into the 10-foot deep snowpack (<strong><a href="https://youtu.be/kzAyDyTQsgs">video</a></strong&gt;). His concerns mirrored mine in Lionhead on Saturday (<u><strong><a href="https://youtu.be/S_gUqe5axGQ">video</a></strong></u&gt;). For today, avalanches are still possible and the danger is rated MODERATE. Do not get on steep slopes or wind-loaded slopes if you get cracking or collapsing.</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://mtavalanche.us17.list-manage.com/track/click?u=6653a830e4819c9e…; target="_blank">observation form</a></strong></u>, email us (<u><strong><a href="mailto:mtavalanche@gmail.com&quot; target="_blank">mtavalanche@gmail.com</a></strong></u>), leave a VM at 406-587-6984, or Instagram (#gnfacobs).</p>