20-21

Natural new snow avalanches at Bridger and N. Madison

Bridger Bowl
Bridger Range
Code
SS-N-R1-D1.5-I
Elevation
8500
Aspect
NE
Latitude
45.81560
Longitude
-110.92300
Number of slides
4
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Natural trigger
R size
1
D size
1.5
Bed Surface
I - Interface between new and old snow
Problem Type
New Snow
Images
Natural new snow slab avalanche in northern Madison
Natural slides across North Bowl road at Bridger
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year
20-21

From obs: "[4/25/21] we toured up Sphinx mountain to have a look at the new snow. Both at the base of the west face and at the summit, new snow totals were approximately 5-10cm. On the approach, evidence of wind loading was minimal. Wind speed increased throughout the day, and we observed more significant wind loading on northern aspects. We found a supportable crust on all aspects of our ascent and descent and did not conduct any stability tests. Cracking on isolated wind loaded areas was observed on the approach.

Northern Madison, 2021-04-27
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    • Sphinx Mountain

    Date
    Activity
    Skiing

    Yesterday morning we toured up Sphinx mountain to have a look at the new snow. Both at the base of the west face and at the summit, new snow totals were approximately 5-10cm. On the approach, evidence of wind loading was minimal. Wind speed increased throughout the day, and we observed more significant wind loading on northern aspects. We found a supportable crust on all aspects of our ascent and descent and did not conduct any stability tests. Cracking on isolated wind loaded areas was observed on the approach. We did perform a ski cut on a northern aspect of the west face and on a western aspect below the face, and found that the new snow did not release. It seemed that low snow accumulation and lower temperatures kept the new snow in place on the Sphinx, but warmer temps and increased wind loading in the coming days may create a wind slab problem.

    Region
    Northern Madison
    Location (from list)
    Sphinx Mountain
    Observer Name
    Erich Schreier

    GNFAC Avalanche Forecast for Mon Apr 26, 2021

    Snowpack and Avalanche Discussion

    <p>Heavy new snow&nbsp;creates potential for&nbsp;dangerous avalanche conditions the next few days. The Bridger Range, Cooke City and southern Madison Range got 10-16” of snow equal to 1.3-1.7” of snow water equivalent (SWE), near Big Sky got 9” of snow equal to 0.9” of SWE, and Hyalite and West Yellowstone got 4-5” equal to 0.4-0.5” of SWE.</p>

    <p>Today, large avalanches can be triggered by skiers, snowmobilers, climbers or hikers traveling on steep, snow-covered slopes. Avalanches will involve the new snow and could break as slabs, wide across or up slopes. Loose snow avalanches could run far and become large, especially where more snow fell. Carefully and continuously assess the stability of the new snow if you travel in avalanche terrain.</p>

    <p>Through the week, anticipate avalanche danger to rise each day with sun and warm temperatures. The new snow will quickly get wet from the&nbsp;sun the next couple days, and wet snow avalanches will be easy to trigger and occur naturally. Later in the week, above freezing temperatures at night will prevent the snowpack from freezing and create potential for deeper, destructive wet snow avalanches. On some slopes there is still weak, sugary snow at the base of the snowpack that could produce large wet slabs (<a href="https://www.mtavalanche.com/images/21/depth-hoar-n-madison"><strong>pho…;, <a href="https://www.youtube.com/watch?v=1PFmB3aoeNI&amp;list=PLXu5151nmAvQDzKmH… snowpack summary video</strong></a>). Plan to start your adventures early in the day and be off and out from underneath steep slopes before they have a wet, unsupportive snow surface. See below for additional general spring snowpack and travel advice.</p>

    <p>We will issue our final snowpack and weather update on Friday. We will continue to share relevant avalanche and snowpack information on our website and social media when available. 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>

    Announcements, Avalanche Education and Events

    Bridger Bowl is closed, and backcountry conditions exist (video). There is no avalanche mitigation or ski patrol rescue. Please stay clear of work areas, snowmobiles, chair lifts and other equipment.

    See our education calendar for an up-to-date list of all local classes.

    The Ramp

    Date
    Activity
    Snowboarding

    1-8” of new snow as of 7:30pm increasing with elevation from 6,000-8,400’ We dug a pit at 7,800’ with about 6” of new snow on a northeast facing slope. Snowpack was about 250cm deep. ECTN 25 on a crust from earlier in the week. One small point release in the new snow when we switched to a south aspect at 7,800’

    Region
    Bridger Range
    Location (from list)
    The Ramp
    Observer Name
    Cole Oshiro-Leavitt
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