20-21

Large natural wind slab on Iceberg Peak, near Cooke

Goose Lake
Cooke City
Code
SS-N-R3-D2-S
Elevation
11200
Aspect
NE
Latitude
45.13500
Longitude
-109.88800
Notes

From obs: "... an avalanche we saw out by Goose Lake yesterday (3/27)... we are pretty sure this wasn't there at 8am. On the way back (5pm) we noticed this large avalanche on the NE face of Iceberg Peak at about 11,200. It broke naturally in the new snow which was drifted heavily by SW winds (20-40mph all day). It appears to be 3-4' deep at the deepest spots, 600' wide, and ran 750'. There is a small area below the upper crown that stepped down, but tough to tell if that was just snow from the start of this storm. We did not notice any other activity in the area..."

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Natural trigger
R size
3
D size
2
Bed Surface
S - Avalanche released within new snow
Slab Thickness
30.0 inches
Vertical Fall
750ft
Slab Width
600.00ft
Images
Large natural wind slab near Iceberg Peak
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year
20-21

Fro obs: "... an avalanche we saw out by Goose Lake yesterday (3/27)... we are pretty sure this wasn't there at 8am. On the way back (5pm) we noticed this large avalanche on the NE face of Iceberg Peak at about 11,200. It broke naturally in the new snow which was drifted heavily by SW winds (20-40mph all day). It appears to be 3-4' deep at the deepest spots, 600' wide, and ran 750'. There is a small area below the upper crown that stepped down, but tough to tell if that was just snow from the start of this storm. We did not notice any other activity in the area..." Photo: M. Cohen

Avalanche Details: Large natural wind slab on Iceberg Peak, near Cooke
Forecast link: GNFAC Avalanche Forecast for Mon Mar 29, 2021GNFAC Avalanche Forecast for Tue Mar 30, 2021
Cooke City, 2021-03-28
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    • Sled triggered large avalanche, McAtee Basin

    Buck Ridge
    Northern Madison
    Code
    AMu-R2-D2-O
    Elevation
    9200
    Aspect
    N
    Latitude
    45.17230
    Longitude
    -111.44300
    Notes

    From obs: "Saw this slope which frequently slides had been triggered on our way out last night. Slid to the ground but I expect it was mostly new snow was there is a larger old crown visible further uphill.... I did see two other small pocket slides yesterday also in new snow on bed surfaces of older slides.... General snowpack is getting very deep now but a thick junk layer remains at the ground everywhere I dug sleds out."

    Number of slides
    1
    Number caught
    0
    Number buried
    0
    Trigger
    Snowmobile
    Trigger Modifier
    u-An unintentional release
    R size
    2
    D size
    2
    Bed Surface
    O - Old snow
    Problem Type
    Persistent Weak Layer
    Images
    Sledder triggered avalanche in McAtee Basin
    Slab Thickness units
    centimeters
    Single / Multiple / Red Flag
    Single Avalanche
    Advisory Year
    20-21

    From obs 3/28/21: "Saw this slope which frequently slides had been triggered on our way out last night [lower left in photo]. Slid to the ground but I expect it was mostly new snow as there is a larger old crown visible further uphill... I did see two other small pocket slides yesterday also in new snow on bed surfaces of older slides... General snowpack is getting very deep now but a thick junk layer remains at the ground everywhere I dug sleds out." Photo: J. Gerardi

    Avalanche Details: Sled triggered large avalanche, McAtee Basin
    Forecast link: GNFAC Avalanche Forecast for Mon Mar 29, 2021
    Northern Madison, 2021-03-28
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    • GNFAC Avalanche Forecast for Sun Mar 28, 2021

    Snowpack and Avalanche Discussion

    <p>Think twice about riding or skiing steep slopes today. Avalanche danger will increase as steady strong winds continue to drift recent snow into thick slabs. Yesterday near Mt. Blackmore a skier remotely triggered an 8-10 foot deep avalanche that broke on weak, sugary snow near the ground (<strong><a href="https://www.mtavalanche.com/node/24732">photos and details</a></strong>), and we heard of a recent natural deep slab in Flanders Creek (<strong><a href="https://www.mtavalanche.com/images/21/natural-deep-slab-near-flanders">…;). These are the first avalanches to break on this deep weak layer since February. The likelihood of triggering a deep slab avalanche remains low, but these slides are a sign that the load of recent snow has made it is possible.</p>

    <p>The most likely type of avalanche you can trigger today is a fresh drift of snow 1-2 feet deep. Yesterday skiers triggered fresh wind slabs in Hyalite (<strong><a href="https://www.mtavalanche.com/node/24731">photo and details</a></strong>, <strong><a href="https://www.mtavalanche.com/node/24735">photo and details</a></strong>), the Bridgers, and the Madison Range (<strong><a href="https://www.mtavalanche.com/images/21/wind-slab-avalanche-pyramid-point…;). Similar slabs will grow larger and easier to trigger through today, and could break deeper on weak snow near the ground, or break wide on a weak layer buried below recent snow. We have found the weak layer below the recent snow to be unstable in some of our snowpits, but not all, near Cooke City (<a href="https://www.youtube.com/watch?v=CZ27CVuKWuA"><strong>Cooke video</strong></a>) and Buck Ridge (<strong><a href="https://www.youtube.com/watch?v=JZ1rnPsoIIg&amp;list=PLXu5151nmAvQDzKmH…;, <strong><a href="https://www.youtube.com/watch?v=zCKlHstJTqc&amp;list=PLXu5151nmAvQDzKmH…;

    <p>Warm temperatures and wind-loading will increase the chances of cornice falls, which could trigger larger avalanches. Lastly, above freezing temperatures and sunny skies today make wet snow avalanches possible. Expect this hazard on lower elevation slopes and slopes that receive direct sun. Where the snow surface gets moist, loose snow avalanches will become easy to trigger.</p>

    <p>There is a long list of avalanche hazards today, and stability will decrease with strong wind and above freezing temperatures. To stay safe, make a plan to avoid wind-loaded slopes and complex terrain, and have options to avoid steep slopes altogether. If you plan to ride on slopes steeper than 30 degrees, carefully evaluate the stability of recent snow and consequences of being caught in a slide. Today, on wind-loaded slopes human triggered avalanche are likely and large natural avalanches are possible. The avalanche danger is CONSIDERABLE on wind-loaded slopes and MODERATE on all 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>

    Upcoming Avalanche Education and Events

    See our education calendar for an up-to-date list of all local classes. Here are a few select upcoming events and opportunities to check out:

    March 29, 6 p.m., Free 1-Hour Avalanche Awareness, online Link to Join HERE

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