Snowpack and Avalanche Discussion
<p>A combination of new snow, wind-drifted snow and persistent weak layers result in dangerous avalanche conditions in Cooke City. <strong>W</strong><strong>ind slab avalanches</strong> on slopes with fresh drifts are the primary concern. Yesterday, Alex and observers saw numerous human-triggered and natural avalanches north of Cooke City that broke 1-2 feet deep on wind-loaded slopes (<a href="https://www.mtavalanche.com/node/34368"><span>observation and photos</span></a>, <a href="https://www.mtavalanche.com/node/34360"><span>photos and details</span></a>). On Sunday, Alex reported unstable drifts in the Republic Creek drainage (<a href="https://www.mtavalanche.com/node/34343"><span>observation and photos</span></a>). Expect similar instability today. Recent avalanches and shooting cracks are bulls-eye indicators of instability.</p>
<p>Yesterday, Alex triggered a<strong> persistent slab avalanche</strong> from flat terrain while investigating a similar slide that riders remotely triggered on Saturday. Both slides were around 2 feet deep, 150-250’ wide, and failed on weak snow that formed in January (<a href="https://www.youtube.com/watch?v=pniI5ENMxMU"><span>video</span></a>, <a href="https://www.mtavalanche.com/node/34344"><span>observation</span></a>). We don’t yet know whether the snowpack has reached a tipping point or whether these will be isolated events. However, taking a step back is prudent. Avoid most slopes over 30 degrees, especially those with more significant consequences.</p>
<p><span>Cautious route-finding is essential because human-triggered avalanches are likely, and the danger is CONSIDERABLE. </span></p>
<p>Mountains in the Southern Gallatin and Southern Madison Ranges and near West Yellowstone are the focal points for <strong>persistent slab avalanches</strong> breaking on weak layers buried 1-3 feet deep. On Sunday, Mark and I rode into Tepee Basin with a pair of snowmobilers involved in an avalanche on Friday. They helped us with some great takeaways from the incident: one at a time on the slopes, never let your guard down and ensure others are watching from a safe location (<a href="https://www.mtavalanche.com/node/34336"><span>observation</span></a>, <a href="https://www.mtavalanche.com/node/34301"><span>details and photos</span></a>, <a href="https://youtu.be/jdtQgYx3MNA?feature=shared"><span>video</span></a>). Spotting a second rider-triggered avalanche in Tepee Basin (<a href="https://www.mtavalanche.com/node/34341"><span>details and photos</span></a>), remotely triggering a similar slide in the Lionhead area last week (<a href="https://www.mtavalanche.com/node/34268"><span>video</span></a>), an avalanche just outside our advisory area in Black Canyon a week ago (<a href="https://www.mtavalanche.com/node/34266"><span>details</span></a>) and a significant collapse in the Taylor Fork demonstrate the extent of this problem. Avoiding steep, upper-elevation, wind-loaded bowls isn’t enough. Thoroughly test for instability associated with persistent weak layers or minimize your exposure to terrain steeper than 30 degrees.</p>
<p><strong>Wind slab avalanches</strong> are possible on steep wind-loaded slopes. These will likely be less than a foot deep but may knock you over or carry you downhill. Avoid these slopes where they might take you into terrain traps like trees, cliffs and gullies.</p>
<p><span>Human-triggered avalanches are possible, and the avalanche danger is MODERATE. </span></p>
<p>Up to 3” of snow fell this morning in the mountains around Bozeman, Big Sky and Island Park. Strong winds drifting recent snow make <strong>wind slab avalanches </strong><span>breaking up to a foot deep </span>the primary concern. Yesterday, a rider took a ride in a small wind slab avalanche near Buck Ridge. He reached out and reminded us to stay vigilant and only expose one at a time to steep slopes (<a href="https://www.mtavalanche.com/node/34357"><span>details and photos</span></a>). Due to their relatively small size, these slides are most dangerous where terrain traps increase the risk. These include large slopes and terrain with cliffs, rocks, trees and gullies. Avoid steep terrain with signs of active or recent wind-loading. Avalanche activity and shooting cracks indicate instability.</p>
<p><span>Human-triggered avalanches are possible, and the danger is MODERATE. </span></p>
Upcoming Avalanche Education and Events
Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar
