20-21

<p>The snowpack from the Bridger Range to West Yellowstone is weak, not getting any stronger and gives me a headache. The problem is a thick layer of weak, sugary facets at the ground called depth hoar. This layer is 1-2 feet thick and is responsible for collapses, whumpfs and many avalanches (e.g. <a href="https://www.mtavalanche.com/node/23867"><strong><u>Tepee avalanche</u></strong></a>). A secondary problem is a thin layer of feathery surface hoar crystals about a foot down (<a href="https://www.mtavalanche.com/images/21/poor-snowpack-structure"><strong>… of layering</u></strong></a>). While the depth hoar is on most slopes, the surface hoar is not. Yesterday, Alex and I rode around Buck Ridge, found it, and added it to our list of concerns. We also saw 7+ avalanches from 5-7 days ago (<a href="https://www.mtavalanche.com/images/21/4-avalanches-near-mcatee-basin"><…;). In our stability test we were able to break the weak snow at the ground which caught our attention and should erase any fantasy thinking about this layer getting stronger&nbsp; (<a href="https://youtu.be/fUK0nUTBSvU"><strong><u>video</u></strong></a>,<strong…; </strong><a href="https://www.mtavalanche.com/images/21/muddy-crk-profile-jan-21"><strong… profile</u></strong></a>). A snowpack with depth hoar is not to be trusted.&nbsp;</p>

<p>Low snowfall and slopes stripped by wind has created a thin snowpack (<a href="https://www.mtavalanche.com/images/21/wind-scoured-mcatee-basin"><stron…;). Thin and weak go hand-in-hand. Folks will continue to trigger an occasional avalanche if they get unlucky or careless. Continue to dig and look for surface hoar and test the weak snow at the ground, but no matter what I find I’m hesitant to get into avalanche terrain.&nbsp;</p>

<p>Given the poor snow structure, recent avalanche activity and two weak layers in the snowpack, the avalanche danger is rated MODERATE.</p>

<p>The mountains around Cooke City have 3” of new snow, enough to improve riding conditions without increasing avalanche danger. These mountains have two layers of concern: feathery surface hoar crystals buried 12-18” deep and a thin layer of weak grains 3 feet under the surface. These layers are not on every slope and there is no quick and easy way to find them without digging. On Tuesday, snowmobilers triggered this layer in Sheep Creek and luckily escaped getting caught, and near Goose Lake skiers saw 2 human triggered slides (<a href="https://www.mtavalanche.com/node/23857"><strong><u>details and photo</u></strong></a>). Dave and his partner were in these mountains Sunday and Monday and treated slopes as though these layers were on every one. His 2 videos explain what to look for (<a href="https://youtu.be/J9oQHYge_gM"><strong><u>video1</u></strong></a&gt;, <a href="https://youtu.be/J9oQHYge_gM"><strong><u>video2</u></strong></a&gt;). For today, the avalanche danger is rated MODERATE since a person could trigger a slide on one of these weak layers.&nbsp;</p>

<p>If you get out, please send us your observations no matter how brief. You can submit them via our <a href="https://www.mtavalanche.com/node/add/snow_observation"><strong><u>websi…;, email (<a href="mailto:mtavalanche@gmail.com"><strong><u>mtavalanche@gmail.com</u></str…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>

<p>The wind is decreasing and there has not been new snow since Monday. The snow from the Bridger Range south to West Yellowstone has a weak structure. There are two layers in the snowpack to be concerned about, one thin and one thick. The thin layer is feathery crystals of surface hoar buried a foot under the surface (<a href="https://www.mtavalanche.com/images/21/buried-surface-hoar-cooke-city"><…;). The thicker layer is sugary, weak grains at the bottom 1-2 feet of the snowpack. Both of these layers are weak and could be triggered.&nbsp;</p>

<p>On Monday and Tuesday snowmobilers triggered slides in Tepee Basin (<a href="https://www.mtavalanche.com/node/23867"><strong><u>photos and details</u></strong></a>) and Buck Ridge (<a href="https://www.mtavalanche.com/images/21/snowmobile-triggered-avalanche-se… Yellowmule photo</u></strong></a>). And on Tuesday skiers saw a recent avalanche on the north face of Mt. Blackmore (<a href="https://www.mtavalanche.com/images/21/slab-avalanche-mt-blackmore"><str…;). The thick layer of weak snow underlying the bottom third of the snowpack is on most slopes. The thin layer of surface hoar is not everywhere, but it’s a good idea to assume it is since we don’t know it’s exact location. This was my advice in Monday’s <a href="https://youtu.be/YzVvIsb7on4"><strong><u>video</u></strong></a&gt; and it still holds true today.&nbsp;</p>

<p>These recent avalanches coupled with skiers still getting collapses/whumpfs, plus poor stability test scores, are signs of the snowpack’s chronic instability. Triggering avalanches is still possible today and the danger is rated MODERATE on all slopes.</p>

<p>The mountains around Cooke City have two weak layers to be concerned about. The first is an inch thick layer of feathery crystals (surface hoar) that is buried 12-18” deep. On Tuesday, a group of snowmobilers triggered this layer in Sheep Creek, and 2 small slides in Goose Creek broke on this layer the same day (<a href="https://www.mtavalanche.com/node/23857"><strong><u>details and photo</u></strong></a>). The second is a thin layer of faceted grains buried 3 feet deep. Both of these layers are scattered and not on every slope. Dave was in Cooke City on Sunday and Monday and recommends either assuming these layers are everywhere, or assessing slopes carefully by digging and testing (<a href="https://www.youtube.com/watch?v=-AhOAQTfkHE&amp;list=PLXu5151nmAvQDzKmH…;, <a href="https://www.youtube.com/watch?v=J9oQHYge_gM"><strong><u>video</u></stro…;). Without new snow or wind-loading triggering avalanches is more difficult, but still possible. Because of buried weak layers and avalanche activity as recent as 48 hours ago, the avalanche danger is rated MODERATE on all slopes.</p>

<p>If you get out, please send us your observations no matter how brief. You can submit them via our <a href="https://www.mtavalanche.com/node/add/snow_observation"><strong><u>websi…;, email (<a href="mailto:mtavalanche@gmail.com"><strong><u>mtavalanche@gmail.com</u></str…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>