From obs on 1/23/21: "I observed a couple older (1-2 week) naturals on E/ESE aspects in the Divide basin, and newer (1-3 days) naturals [shown in photo] on the NE side of Divide and an east aspect at the head of the Maid of the Mist basin." Photo: S. Reinsel
<p>Large avalanches are possible to trigger due to a layer of weak, sugary snow near the ground, which is buried 2-3 feet deep on many slopes. Minimal weight has been added to the snowpack over the last few days. It is slowly becoming more difficult to trigger an avalanche, but the weak layer at the ground is slow to gain strength and remains fragile. Yesterday at Lionhead we had unstable, collapsing and propagating stability tests, and saw recent avalanches from the past 4-10 days (<strong><a href="https://www.youtube.com/watch?v=HtHMcXwo3mw&list=PLXu5151nmAvQDzKmH…;, <strong><a href="https://www.mtavalanche.com/images/21/lionshead-ridge-profile-jan-23">s… profile</a></strong>, <strong><a href="https://www.mtavalanche.com/images/21/natural-avalanche-near-lionhead">…;). On Thursday, Doug and I were on Buck Ridge and had the sugary snow near the ground break in our stability tests (<a href="https://youtu.be/fUK0nUTBSvU"><strong>video</strong></a>,<strong> </strong><a href="https://www.mtavalanche.com/images/21/muddy-crk-profile-jan-21"><strong… profile</strong></a>).</p>
<p>There is also a thin layer of surface hoar buried 8-10” deep (<a href="https://www.mtavalanche.com/images/21/poor-snowpack-structure"><strong>… of layering</strong></a>) that we found at Lionhead, Buck Ridge and Beehive. This layer has not propagated in stability tests or produced avalanches (except in Cooke City, see below). It is easy to dig down a couple feet to look for and test this layer.</p>
<p>Yesterday in the Bridger Range, moderate downhill winds on the east side of the range drifted snow into hard slabs across mid-elevation terrain, far below the ridgeline. Today these slabs could be unstable in areas like Saddle Peak or The Throne.</p>
<p>The primary factor limiting our terrain selection is the sugary snow at the ground. Until that can be trusted we are avoiding most slopes steeper than 30 degrees. Simple, small slopes with low consequences may present acceptable risk to ride down, across or under. Travel on or underneath any steep slope requires careful thought about the snowpack and consequences of a slide. Today, large avalanches are possible to trigger and the avalanche danger is rated MODERATE.</p>
<p>Yesterday near Cooke City, a snowmobiler triggered an avalanche, was partially buried to his waist and uninjured (<strong><a href="https://www.mtavalanche.com/node/23885">limited details</a></strong>). There are two buried weak layers on some slopes near Cooke City which make avalanches possible. A layer of surface hoar buried 12-18” deep produced avalanches, cracking and collapsing over the last week (<strong><a href="https://www.mtavalanche.com/node/23858">snowmobile triggered avalanche details</a></strong>, <a href="https://www.mtavalanche.com/node/23857"><strong>human triggered slides details and photo</strong></a>), and there is a weak layer of sugary snow buried 2-3 feet deep. Although these layers do not exist on all slopes, you can avoid avalanches by avoiding slopes steeper than 30 degrees (see Dave’s videos from last weekend: <a href="https://youtu.be/J9oQHYge_gM"><strong>video1</strong></a>, <a href="https://youtu.be/J9oQHYge_gM"><strong>video2</strong></a>). Diligently assess the snowpack before riding steep slopes. Review recent avalanche activity and media before you head out (<strong><a href="https://www.mtavalanche.com/forecast/cooke-city">Cooke regional page</a></strong>), and dig to look for buried weak layers on slopes similar to where you plan ride. Today avalanches are possible and the avalanche danger is rated MODERATE.</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>website<…;, email (<a href="mailto:mtavalanche@gmail.com"><strong>mtavalanche@gmail.com</strong></a…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>
See our education calendar for an up-to-date list of all local classes. Here are a few select upcoming events and opportunities to check out:
We saw this natural avalanche on 1/23/21. It likely occurred in the past week. SE aspect at 9,200', Photo: GNFAC
CCMS called and said a rider triggered a
slide
about 1/4 mile north of Huckelberry Lake on a south facing slope. It trashed a rental sled. The rider was at the crown when it broke and was above most of the debris. He was only buried to his knees and was uninjured. No details on size or depth of
slide
. A close call.
<p>Buried persistent weak layers make human triggered avalanches possible today. A layer of weak, sugary snow near the ground is buried 2-3 feet deep on many slopes and has produced large avalanches this season. The most recent reported was triggered by a snowmobiler Tuesday in the southern Madison Range (<strong><a href="https://www.mtavalanche.com/node/23867">photos and details</a></strong>). On Thursday Doug and I found this layer on Buck Ridge, in addition to a thin layer of surface hoar buried 8-10” deep (<a href="https://www.mtavalanche.com/images/21/poor-snowpack-structure"><strong>… of layering</strong></a>). The sugary snow near the ground broke in our stability test which reminds us it remains unstable and is not going anywhere (<a href="https://youtu.be/fUK0nUTBSvU"><strong>video</strong></a>,<strong> </strong><a href="https://www.mtavalanche.com/images/21/muddy-crk-profile-jan-21"><strong… profile</strong></a>). The surface hoar is not on all slopes, but the sugary depth hoar near the ground is on most.</p>
<p>Light wind with a couple inches of snow the last few days combined with continued calm, clear weather today gives weak layers a reprieve from additional load. Triggering an avalanche is becoming more difficult, but the possibility and consequences require careful terrain selection and diligent snowpack assessment. Be cautious of travel on and underneath slopes steeper than 30 degrees. Large avalanches are possible to trigger and the avalanche danger is rated MODERATE.</p>
<p>In the mountains near Cooke City a layer of surface hoar buried 12-18” deep produced avalanches, cracking and collapsing over the last week. On Tuesday, snowmobilers triggered an avalanche on this layer in Sheep Creek (<strong><a href="https://www.mtavalanche.com/node/23858">details</a></strong>), and near Goose Lake skiers saw 2 human triggered slides that we suspect broke on this layer (<a href="https://www.mtavalanche.com/node/23857"><strong>details and photo</strong></a>). Additionally, a weak layer of sugary, faceted snow buried 2-3 feet deep exists on some slopes. Dave rode near Cooke City last Sunday and Monday and traveled as if these weak layers are on all slopes (<a href="https://youtu.be/J9oQHYge_gM"><strong>video1</strong></a>, <a href="https://youtu.be/J9oQHYge_gM"><strong>video2</strong></a>). Although these layers do not exist on all slopes, you can avoid avalanches by avoiding slopes steeper than 30 degrees. Otherwise, you have to diligently assess the snowpack which starts with a thorough review of recent avalanche activity (<strong><a href="https://www.mtavalanche.com/avalanche-activity">activity log</a></strong>) and media from the region (<strong><a href="https://www.mtavalanche.com/forecast/cooke-city">Cooke regional page</a></strong>), and should include digging to look for these layers before riding steep slopes. Today avalanches are possible and the avalanche danger is rated MODERATE.</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>website<…;, email (<a href="mailto:mtavalanche@gmail.com"><strong>mtavalanche@gmail.com</strong></a…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>
See our education calendar for an up-to-date list of all local classes. Here are a few select upcoming events and opportunities to check out:
