20-21

From obs.: "Kicked off a larger than expected cornice as we skinned up the ridge on the W side of Beehive basin. Wind was blowing 20-ish across the opening, cornice had grown pretty good-sized for so little snow. I was making a turn on skins to get back away from the edge when the cornice gave way, probably pulled 25 feet end to end and broke a good 5 feet back from the lee edge of the cornice. I was able to get off the cornice and avoid going over the edge. No activity on the slope below after cornice drop,...

Avalanche Details: Skier triggered large cornice, Beehive
Northern Madison, 2020-12-20
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    • Beehive Basin, West side

    Date
    Activity
    Skiing

    Kicked off a larger than expected cornice as we skinned up the ridge on the W side of Beehive basin. Wind was blowing 20-ish across the opening, cornice had grown pretty good-sized for so little snow. I was making a turn on skins to get back away from the edge when the cornice gave way, probably pulled 25 feet end to end and broke a good 5 feet back from the lee edge of the cornice. I was able to get off the cornice and avoid going over the edge. No activity on the slope below after cornice drop, which was encouraging, although there was a decent hard slab that pulled out just below the ridge when the cornice dropped onto it. Pics attached for reference. Hard slab on the edges was about 10" deep, some big chunks of cornice on the slope for any future riders.

    Overall conditions were pretty crappy. Shallow pack; the deepest we had was 95cm with significant layers at 25cm and 60 cm (from surface). Lots of rocks and trees to dodge on the ski out.

    Region
    Northern Madison
    Location (from list)
    Beehive Basin
    Observer Name
    Garrett Stevens

    YNP Plateau along US-191

    Date
    Activity
    Skiing

    Returned to Telemark Meadows to see if the new snow since Thursday improved the skiing. Didn't ski. From about Specimen Creek, the weather was 22-23 F and freezing rain. There was a 1/4" ice crust on the surface at the TM turn-around. Assume the same in the other areas along US-191 including Bacon Rind. Crazy to see that much ice accumulation here (looks more like New England / upstate NY).

    Drove to Beehive where it was partly sunny, windy and about 30. As reported, thin cover with facets on the ground but less overall snow than in the Park. South facing slopes did ski OK as the facets are not present due, I guess, to sun exposure. The bottom 6-8" are a cohesive mass of large crystals firmly bonded to the ground with what snow has fallen pretty firmly bonded. Problem, of course, is south facing is even thinner snowpack. I made a good PETEX sacrifice to Ullr.

    Region
    Southern Madison
    Observer Name
    Alan Crawford

    Small crowns on Barronette

    COOKE CITY
    Cooke City
    Code
    Latitude
    45.02020
    Longitude
    -109.93800
    Notes

    From email: "We observed a couple more recent slab avalanches today on the east face of Barronette too.  Each slide had similar characteristics to the avalanche photos from yesterday:  about 1' deep, and 50' wide." 

    Number of slides
    1
    Number caught
    0
    Number buried
    0
    Slab Thickness units
    centimeters
    Single / Multiple / Red Flag
    Single Avalanche
    Advisory Year
    20-21

    GNFAC Avalanche Forecast for Sun Dec 20, 2020

    Snowpack and Avalanche Discussion

    <p>From Big Sky to West Yellowstone 1-2 feet of weak, sugary snow on the ground will struggle to hold the weight of fresh drifts that formed from strong westerly wind. Last week Ian was in Taylor Fork and found unstable, soft drifts (<strong><a href="https://www.youtube.com/watch?v=eAZKRKDi-pg&amp;list=PLXu5151nmAvQDzKmH…;), and Doug triggered a 1 foot deep soft slab on a small slope near West Yellowstone (<strong><a href="https://www.mtavalanche.com/node/23272">photo</a></strong&gt;). On Friday, we got reports of multiple slides triggered by snowmobiles, groomers, snowplows, and by explosives at the ski resorts (<a href="https://www.mtavalanche.com/images/20/groomer-triggered-road-cuts"><str…;, <a href="https://www.mtavalanche.com/images/20/small-snowmobile-triggered-slides…; </strong><a href="https://www.mtavalanche.com/images/20/snowplow-triggered-slide-near-big…;).</p>

    <p>Due to the very poor snow structure, slabs that grew over the last week have not stabilized and remain easy to trigger. Avalanche danger is CONSIDERABLE on wind-loaded slopes and MODERATE on non-wind loaded slopes. Near West Yellowstone, heavy snowfall and wind today will increase the avalanche danger to CONSIDERABLE. Avoid travel on or underneath steep, wind-loaded slopes.</p>

    <p>Near Cooke City, avalanche danger is elevated due to new snow and strong wind that will create fresh slabs. Today, these slabs are possible to trigger and large enough to bury or badly injure a person. Expect stability to decrease through the day as more snow and wind grow larger slabs. Be extra cautious of wind-loaded slopes where thick drifts form. The snowpack near Cooke city is 3-5 feet deep and generally lacks widespread buried weak layers (<a href="https://www.youtube.com/watch?v=71V0bipTxfY"><strong>video</strong></a&…;). However, we have seen and heard evidence of weak snow buried 1-2 feet deep on some slopes. This includes a few avalanches west of Cooke City last week which broke 100 feet wide on a layer of sugary snow (<a href="https://www.mtavalanche.com/node/23292"><strong>photo</strong></a&gt;). Today the avalanche danger is MODERATE.</p>

    <p>In the mountains near Bozeman, strong westerly winds over the last 24 hours formed thick drifts that are unstable on steep slopes. These drifts can’t be trusted to hold the weight of a person because the snowpack below has widespread sugary weak layers (<strong><a href="https://www.mtavalanche.com/images/20/snowpit-bridger-29-nov">photo</a>…;, <strong><a href="https://www.youtube.com/watch?v=JrjrgTLRff0&amp;feature=youtu.be">video…;). Avoid steep wind-loaded slopes today. These can range from hard slabs near ridgelines to soft slabs in the trees. On non-wind loaded slopes, a lack of new snow to form a slab over the weak foundation makes avalanches unlikely. If you are unsure which slopes are wind-loaded, be cautious of any slope steeper than 30 degrees. Today the avalanche danger is MODERATE on wind-loaded slopes and LOW on other slopes.</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>

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