22-23

Mt Ellis Pits and Video

Date
Activity
Skiing

We skinned up to Mt. Ellis summit today. We dug our first pit on the approach at 7,700’. The first pit on a NE aspect was thin (HS = 80 cm/2.5 ft) with an ECTN 11 and 22 in the top half of the snowpack. In this shallow snow we saw depth hoar and facets at the ground. We dug our second pit near the Burn below the summit of Mt. Ellis (8,100’). This NE aspect had 2-3 ft of snow (85 cm), and we had an ECTX.

Both pits showed a shallow snowpack with facets at the bottom. Moving forward, the thin snowpack will be more susceptible to faceting. Also, the poor structure of this snowpack (dense snow on top of facets) could be a concern with more snow. These two things show us that we should continue to assess the snowpack around Mt. Ellis.

Region
Northern Gallatin
Location (from list)
Mt Ellis
Observer Name
GNFAC

Middle Peak pit and stability tests

Date
Activity
Skiing

Yesterday we toured into Middle Basin to check out the new snow. It appeared that, throughout the day, wind shifted towards the south and wind loading was isolated to exposed sections of ridge line. Snow was falling at about 2cm/hour from 9-11am, and slowly reduced until skies began to clear around 2pm. Whiteout conditions kept us from heading to the summit of Middle Peak, and we stopped at the entrance of the “buttcrack” to check the snow. At our test location on the SE face of middle, just to the north of the entrance of the chute, wind loading was minimal and we observed ~ 5 inches of fresh snow. Our pit revealed a relatively upright snowpack. Stability tests pointed to a layer of concern at 60cm, where there was an interface between rounds and faceting rounds.  

Region
Northern Madison
Location (from list)
Middle Basin
Observer Name
Erich Schreier

On Dec 9, 2022 we triggered this avalanche while riding across the lower angle slope below. It broke 3-6+' deep and 300' wide. One rider was caught and carried, and luckily nobody was injured. Photo from 12/10: GNFAC

Avalanche Details: Remote triggered deep slab, Fisher
Forecast link: GNFAC Avalanche Forecast for Wed Dec 14, 2022GNFAC Avalanche Forecast for Fri Dec 16, 2022
Cooke City, 2022-12-12
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    • On Dec 9, 2022 we triggered this avalanche while riding across the lower angle slope below. It broke 3-6+' deep and 300' wide. One rider was caught and carried, and luckily nobody was injured. Photo from 12/10: GNFAC

    Avalanche Details: Remote triggered deep slab, Fisher
    Forecast link: GNFAC Avalanche Forecast for Thu Dec 15, 2022GNFAC Avalanche Forecast for Fri Dec 16, 2022GNFAC Avalanche Forecast for Sat Dec 17, 2022
    Cooke City, 2022-12-12
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    • GNFAC Avalanche Forecast for Mon Dec 12, 2022

    Snowpack and Avalanche Discussion

    <p><span><span><span><span><span><span>A person can trigger a large avalanche that breaks on weak layers buried 2-3 feet deep, or deeper on heavily wind-loaded slopes. Minimal new snow and light winds are giving the snowpack a break from added weight, and the likelihood of triggering a large avalanche has decreased. However, the consequences remain large and potentially deadly. These avalanches can be triggered from low angle terrain below steep slopes, and can be triggered by the second, third, or tenth person on a slope.&nbsp;</span></span></span></span></span></span></p>

    <p><span><span><span><span><span><span>Natural and human-triggered avalanches that occurred over the last couple weeks near West Yellowstone and Cooke City are examples of what is possible (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=35NYGUBLhbg&amp;t=5s"><span><span><span… avalanche 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.youtube.com/watch?v=N8CtHy3efxs"><span><span><span><strong>… Pass 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/27113"><span><span><span><strong><span… photo and details</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). On Friday, my partner and I triggered an avalanche that broke 3-6 ft deep and 500 feet above us while we were crossing below a steep slope near Lulu Pass north of Cooke City (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=7sKzKPXI1dM"><span><span><span><strong>…; </span></span></strong></span></span></span><a href="http://www.mtavalanche.com/images/22/fisher-avalanche-full-extent"><spa…;). The snowpack was less than 3 feet deep where we triggered the avalanche from, but the fracture extended up to the deeper, heavily wind-loaded ridgeline.&nbsp;</span></span></span></span></span></span></p>

    <p><span><span><span><span><span><span>Snowpack stability assessment for these large avalanches is tricky. Keep a wide margin for error and avoid travel on and underneath steep slopes that you suspect have a buried weak layer, especially slopes that are heavily loaded with wind-drifted snow. Today, large human-triggered avalanches are possible and avalanche danger is MODERATE.</span></span></span></span></span></span></p>

    <p><span><span><span><span><span><span>Over the past week, strong south-southwest wind blew new snow into dense drifts that can avalanche under the weight of a person on steep slopes (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/27160"><span><span><span><strong><span… Ridge wind slab</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/27169"><span><span><span><strong><span… Range wind slabs</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/22/small-slide-blackmore"><span><spa…. Blackmore wind slab</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Yesterday I looked at the snowpack on Saddle Peak in the Bridger Range and found these hard wind slabs are still possible to trigger (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=XrYqTxRt4go&amp;list=PLXu5151nmAvTi1DBS… Peak video</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>), and deeper avalanches will become possible when there is snow and wind-loading. Although recently formed wind slabs are relatively shallow (6-10”), they could propagate wide and are especially hazardous if they push you into trees, rocks or over a cliff. Doug was ice-climbing in Hyalite on Friday and found a 10” deep drift sitting over a thin weak layer (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=rRbw4FFs4i0"><span><span><span><strong>… gullies video</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). A setup like this makes wind slabs possible to trigger for many days after they form. Before crossing or riding steep slopes, carefully assess the snowpack for slabs resting over weak layers and consider the consequences of even a small slide. The avalanche danger is MODERATE.</span></span></span></span></span></span></p>

    <p><span><span><span><span><span><span>If you get out, please share avalanche, snowpack or weather observations via our</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/add/snow_obs"><span><span><span><span>…; </span></span></span></span></span></span><span><span><span><strong><span><u><span><span>website</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, email (</span></span></span></span></span></span><span><span><span><strong><span><span>mtavalanche@gmail.com</span></span></strong></span></span></span><span><span><span><span><span><span>), phone (406-587-6984), or Instagram (#gnfacobs).</span></span></span></span></span></span></p>

    <p><span><span><span><span><span><span>Recent new snow and strong winds make avalanches possible for a person to trigger today. Last Friday, Dave and Ian found up to 18” of new snow while riding in Yale Creek and drifts up to 4 ft deep (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=06pszOXXgOQ"><span><span><span><strong>… video</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). They also found weak layers similar to what we’ve seen in Lionhead (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/27153"><span><span><span><strong><span… observations</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Be extra cautious of steep slopes, especially slopes that are wind-loaded.</span></span></span></span></span></span></p>

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