We triggered a wind slab. It propagated about 200 ft wide and was 3 ft at the deepest point. Interestingly on the edges and near the bottom (downhill side) of the slab it was only a few inches deep. It broke on the interface between the wind loaded snow and the light and dry snow we received a few days ago. Photo: A Shafer
We triggered a wind slab. It propagated about 200 ft wide and was 3 ft at the deepest point. Interestingly on the edges and near the bottom (downhill side) of the slab it was only a few inches deep. It broke on the interface between the wind loaded snow and the light and dry snow we received a few days ago. Photo: A Shafer
We triggered a wind slab. It propagated about 200 ft wide and was 3 ft at the deepest point. Interestingly on the edges and near the bottom (downhill side) of the slab it was only a few inches deep. It broke on the interface between the wind loaded snow and the light and dry snow we received a few days ago. Photo: A Shafer
Toured up the ramp this morning, found between 3-6" of new snow on the skin track, winds were fairly strong from the north/northwest and moving snow. Snow was falling heavily for the duration of the tour. As we made our last switchback in the ridge line meadow (8500ft directly east facing) near the top of the ramp, we triggered a wind slab. It propagated about 200 ft wide and was 3 ft at the deepest point. Interestingly on the edges and near the bottom (downhill side) of the slab it was only a few inches deep. It broke on the interface between the wind loaded snow and the light and dry snow we received a few days ago. When we entered the upper meadow there was no evidence of tracks from the day before. Further down the ramp we found cross loaded rolls that produced shooting cracks and collapses, and active snow loading from the new snow and wind. A half hour later on our ski down, the skin track was partially buried by new snow as we exited the area.
Little Ellis now has (barely) enough cover to be skiiable (at least up high - still marginal lower down). Dug a pit on the NE aspect 100 yard NE of the summit. Found unconsolidated snow all the way down to the ground (roughly 36" deep). Negative ECT.
<p><span><span><span><span><span><span>Across our forecast area dangerous avalanche conditions exist. Frequent snowfall over the last 2 weeks has built thick, heavy slabs of snow above weak layers that are now buried 2-4 feet deep. Human triggered avalanches are likely, and can be large enough to bury a person, or possibly larger. Where snowfall is heavy this morning the likelihood of triggering an avalanche will increase during the day, and natural avalanches are possible.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Near Cooke City received 13” of heavy snow from Thursday to yesterday afternoon which prompted an avalanche warning yesterday, and there was a big natural avalanche on </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33306"><span><span><span><strong><span… Mtn.</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span> which broke 4 feet deep and hundreds of feet wide. During the last round of snow, there were similarly large natural avalanches on </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33142"><span><span><span><strong><span… Mountain</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span> and </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33267"><span><span><span><strong><span… Peak</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>. This type of </span></span></span></span></span></span><span><span><span><strong><span><span>persistent slab avalanche </span></span></strong></span></span></span><span><span><span><span><span><span>is similar to what you can trigger today.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Yesterday Mark snowmobiled in Cabin Creek near West Yellowstone where he had widespread collapsing and saw relatively large avalanches on road cuts (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=kLYL6RlovQY"><span><span><span><strong>…; </span></span></strong></span></span></span><span><span><span><span><span><span>and </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33297"><span><span><span><strong><span… with photos</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). These are clear signs that a person can easily trigger an avalanche on slopes steeper than 30 degrees, or from flatter terrain connected to steep slopes. We have received daily feedback that the snowpack is unstable via collapsing, whumpfs, and avalanches. </span></span></span></span></span></span><a href="https://www.mtavalanche.com/snow-observations-list"><span><span><span><… out our observations page</span></span></u></span></strong></span></span></span></a><span><span><span><strong><span><span> </span></span></strong></span></span></span><span><span><span><span><span><span>to view the latest reports of these red flags.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Winds have been generally light with the recent snowfall, so there is plenty of soft snow to be drifted into slabs by any increase in wind speed. Last night a few </span></span></span></span></span></span><span><span><span><strong><span><span>wind slabs</span></span></strong></span></span></span><span><span><span><span><span><span> probably formed from moderate southwest winds. These can be a hazard on their own, and increase the chances of triggering larger persistent slab avalanches on wind-loaded slopes. </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Yesterday’s snow fell as temperatures warmed which caused heavier snow to form slabs over lower density snow. This setup caused </span></span></span></span></span></span><span><span><span><strong><span><span>storm slab avalanches </span></span></strong></span></span></span><span><span><span><span><span><span>to break within the new snow (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33296"><span><span><span><strong><span… observation</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). These slabs typically stabilize quickly, but a few might remain unstable today. Cracking across the snow surface is a sign you could trigger slabs of new or wind-drifted snow.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Enjoy the new snow while staying on slopes less than 30 degrees, and away from flatter terrain below these steep slopes (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=wez-MVpRq5w"><span><span><span><strong>…’s video</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). New snow and buried weak layers make human-triggered avalanches likely today, and the avalanche danger is CONSIDERABLE throughout the forecast area.</span></span></span></span></span></span></p>
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From IG 1/3: “Buck ridge today. NE aspect. Probably 100’ wide and at least 3’ deep. Looked like it was triggered by a snowmobiler earlier in the day.”
From IG 1/3: “Buck ridge today. NE aspect. Probably 100’ wide and at least 3’ deep. Looked like it was triggered by a snowmobiler earlier in the day.” Photo: P Rockwell
From IG 1/3: “Buck ridge today. NE aspect. Probably 100’ wide and at least 3’ deep. Looked like it was triggered by a snowmobiler earlier in the day.” Photo: P Rockwell
