Black Bear Canyon Avalanche, W Yellowstone
Riders in Black Bear Cayon saw a small avalanche on a wind loaded slope that recently happened, either on 01/14 or the day before on 01/13.
Riders in Black Bear Cayon saw a small avalanche on a wind loaded slope that recently happened, either on 01/14 or the day before on 01/13.
A small avalanche was seen in Black Bear Canyon on 01/14. This was a recent avalanche that happened today or yesterday 01/13.
From email: "Lots of hand pits to look for the SH and only found it in open areas at higher elevations. The SH was 10-15mm in size, well intact and "sturdy", overlaying small-grained facets. In hand pits, the column would fail upon isolation, yet the slab wasn't very cohesive, even in windloaded areas. The hand pits were failing on the facets underneath the SH. Some cr, co at higher elevations.
One crown on the Middle Siren, probably part of the last cycle.
Winds were L-M out of the south and S-1 snow starting at 11am. 1cm of new by end of day. "
From obs: "We observed widespread shooting cracks on all ridges and all NE facing slopes. Cracks would propagate up to 200’ in front." O. Robinson
A small avalanche was noted in Black Bear Canyon on a northeast facing slope. Snow was wind loaded, cornices were seen on nearby slopes. This appeared to be storm slab and likely rider triggered. Slope was greater than 30 degrees.
Observed wind slabs forming on top of weak snow. Saw cracking as well. Snowing and blowing on the way out. Photo taken near Texas meadows at 7800’
We observed widespread shooting cracks on all ridges and all NE facing slopes. Cracks would propagate up to 200’ in front. Heavily wind effected sastrugi conditions.
<p><span><span><span><span><span><span>The snowpack is unstable and human-triggered avalanches are likely. Over the last week winds drifted new snow into cohesive slabs on top of a very weak snowpack (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/24/surface-hoar-stripe-underneath-sl… photo</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/24/large-buried-surface-hoar-layer">…;, </span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=K_t6Fi6wUC4&list=PLXu5151nmAvSH326z… of weak layers</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>There were natural avalanches mid-week near Cooke City (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/29906"><span><span><span><strong><span…;, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/29921"><span><span><span><strong><span…;) and Big Sky (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/29873"><span><span><span><strong><span…;), and over the last few days skiers and riders triggered avalanches (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/avalanche-activity"><span><span><span><stro… activity</span></span></u></span></strong></span></span></span><span><span><span><span><span><u><span><span> </span></span></u></span></span></span></span></span><span><span><span><strong><span><u><span><span>list</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Many recent avalanches were triggered remotely, from a distance, meaning you could trigger a slope from lower angle terrain adjacent to or below steeper slopes (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=aTnE5gzG1sc"><span><span><span><strong>… Fork video</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, </span></span></span></span></span></span><a href="https://youtu.be/QNkJeGFSPYs"><span><span><span><strong><span><u><span>… video</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/29915"><span><span><span><strong><span… City photos</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>A break from snowfall and wind-loading is allowing snow stability to slowly improve, but the very weak snowpack means it remains easy to trigger a large avalanche. With persistent weak layers, as stability slowly improves snowpack evaluation becomes tricky. Snowpack tests may give false-stable results and a slope might allow multiple tracks before it breaks. Any slope has potential to slide if it has a cohesive, supportable slab sitting on top of weak, sugary snow.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Careful snowpack evaluation and cautious route finding are required. Be extra cautious of travel on or below slopes steeper than 30 degrees, especially previously wind-loaded slopes. Avalanche danger is CONSIDERABLE.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Recent snow has drifted into slabs on top of a very weak snowpack (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=GJxMtiIQGbs"><span><span><span><strong>… Range video</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Avalanches are possible to trigger, especially on wind-loaded slopes. Watch and feel for signs of wind drifting, such as cracking across the snow surface, cornices, or smooth rounded pillows of snow. Avoid steep slopes that have these signs. The weak snowpack can also cause facet sluffs that gouge deep into the snowpack and run long distances (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=Y0LROtnc7Us"><span><span><span><strong>… Ridge video</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Be cautious of long, sustained steep slopes where these may occur, especially if there are consequences like rocks, trees or cliffs. Carefully evaluate the snowpack and consequences of an avalanche before traveling on or below steep slopes. Avalanches are possible to trigger and the avalanche danger is MODERATE.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>The cold temperatures create higher consequences of an accident. Any bad situation can quickly become worse.</span></span></span></span></span></span></p>
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From email on 01/13: "From Miller Ridge today, I had a brief look into Sheep Creek, and to the mountains south of Cooke City, and observed 7 fresh slab avalanches (that happened in the last 1-3 days). Will send photos of them later if I can get better views.
Most of them were on NEerly aspects, and appeared to be on the new/old Jan. 5th interface. Mid and upper elevations, most commonly in wind loaded terrain. Some propagating a few hundred feet wide. "