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
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
We dug a pit near the base of a 35-40 degree slope. Snow depth was 155cm.
ECT results were as follows:
ECTN 15 - 25cm down on the known layer of buried surface hoar. Clear failure at this layer but no propagation.
ECTP 23 - 70cm slab failed & propagated on weak sugary facets at the base of snowpack.
There were multiple snowmobile highmark tracks on this slope that looked to be from the day before and no signs of snowpack failures from those tracks. Consistent with the forecast for cooke, the layer of buried surface hoar was harder to detect throughout the day but the sugary facets at the base of the snowpack were present everywhere we rode.
2 slides on the South west side of Sheep mtn. Crown looked to be 1-2 feet high. Both where triggered by timbersleds, judging by tracks going into the avy area.
After reading this AMs forecast I may have some more information on the AMu reported near Cooke. We were up on the Henderson bench and saw what could have been a crown from a distance. Hard enough to tell if it was an avalanche or sled track that I didn’t report it. SW aspect of sheep mountain around 9800 ft, on the R as you drive up to Lulu. Seems possible this could have been it? Not a lot of S aspects or bigger terrain 1/4 mike N of Huckleberry... I would estimate D2 depth 30-60 cm. Crappy photo attached, potential crown marked.
<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.
