24-25

Lionhead Jan 23

Date
Activity
Snowmobiling

We went to Lionhead, seeking some of the thinnest and weakest snow. We found relatively thin snow - the snowpack was mostly a 1 meter deep (3.2 ft). It was supportive for sleds and you could walk on top with about 6-8 out of every 10 steps not punching through to the ground. This is because there is a very cohesive slab on top of the early December facets.

What surprised us was how stubborn that weak layer was in our tests. We dug in 4 different places on E, E, E, and NW aspects between 8000 and 9200 feet. ECTs either wouldn't even break or would propagate on the weak layer after mid- to high 20s for taps.

We observed some new facets near the snow surface that formed last weekend during very cold weather. On Lionhead Ridge we found these facets capped by a hard but thin (~4 inch thick) wind slab. 
 

Summary

  • The early December faceted layer seems mostly dormant for now.
  • Wind slabs are the main problem and they will be extra sensitive as more snow comes Friday providing winds more ammo to make the wind slabs deeper. Because these wind slabs may be resting on facets, they could stay a problem for sometime.
  • We did not get a chance to map how widespread or isolated this wind slab/facet combo is.

 

 

 

Region
Lionhead Range
Location (from list)
Lionhead Ridge
Observer Name
Staples & Zinn

GNFAC Avalanche Forecast for Thu Jan 23, 2025

Snowpack and Avalanche Discussion

<p><span><span><span><strong><span><span>Wind slab avalanches</span></span></strong></span></span></span><span><span><span><span><span><span> are the primary problem mostly from strong winds on Tuesday and late last week that blew generally from the W and some NW. On Tuesday, ski guides near Cooke City spotted a </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33805"><span><span><span><span><span><… ft wide wind slab</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span> that released naturally.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><strong><span><span>Larger persistent slab avalanches</span></span></strong></span></span></span><span><span><span><span><span><span> that could break on old faceted layers 1-2 feet above the ground have become much less frequent. The peak instability was almost two weeks ago after a long period of sustained snowfall following Christmas. With only light snowfall trickling in since then, the likelihood of triggering one of these has dropped significantly but the possibility remains.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Faceted layers of snow that cause persistent slab avalanches are like relationships - they can break in an instant, but take time to repair and build trust. With several large avalanches last week near Cooke City (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33528"><span><span><span><span><span><…; and </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33544"><span><span><span><span><span><…;), one in the </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33584"><span><span><span><span><span><… Madison Range</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>, and one </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33790"><span><span><span><span><span><… sign of instability last Sunday near Cabin Creek</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>, I need a little more time to build the trust to enter big terrain.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>For these reasons today the avalanche danger is MODERATE.</span></span></span></span></span></span></p>

<p><span><span><span><strong><span><span>Wind slab avalanches </span></span></strong></span></span></span><span><span><span><span><span><span>are the main problem in the mountains near Bozeman, Big Sky, and Island Park. To be honest, they are always a concern to varying degrees, and I’ve been fooled many times thinking wind slabs had stabilized only to find one that hadn’t. Increased winds today may form new, shallow wind slabs and keep older wind slabs unstable.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><strong><span><span>Today seek out slopes sheltered from the wind</span></span></strong></span></span></span><span><span><span><span><span><span>. Dave and his partner </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33816"><span><span><span><span><span><… this exact strategy yesterday</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span> in the northern Bridgers even though it was not easy to find a wind sheltered slope. Persistent slab avalanches are unlikely, and old weak layers have gained strength on most slopes where the snowpack is over about 5 feet deep.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The avalanche danger is MODERATE on wind loaded slopes and LOW on non wind loaded slopes.</span></span></span></span></span></span></p>

KING AND QUEEN OF THE RIDGE

Do you like to hike? Do you like to ski/ride? Then the King & Queen of the Ridge on 2/1 is for you. Hike, ride and raise money for the Friends of the Avalanche Center at Bridger Bowl this year! Join this fun event to promote and support avalanche safety and awareness! Fundraising prizes for the top 5 individuals who raise over $500.

Variable Conditions at the Throne

Date
Activity
Skiing

We rode to the motorized boundary and toured up the shoulder of the Throne, poked out to the north-facing runs at the top, and then moved to the south-aspect gully from the upper saddle. 

Winds have worked over many slopes near the Throne. We found some slopes stripped nearly to dirt with the snow blown off to who knows where, and others had wind-sculpted sastrugi. Trees were broken off, and debris littered the snow surface. We probed for snow depths. On the east face, depths ranged from 20 cm to 100 cm on the shoulder (we may have missed deeper spots). At the upper portion of the north-facing run, we found 50-75 cm depths. The south face had a 115 cm depth.

There was some isolated wind-loading mid-slope. We saw one old crown that was nearly drifted in on a steep break over at mid-elevation on the east face. 

Somehow, we found a slope sheltered from the wind's effects. Because the danger is low on non-wind-loaded slopes, we considered traveling down through avalanche terrain. Before we did, we assessed stability to give us one last chance to turn around, and we followed safe travel practices, exposing one skier at a time to potentially hazardous terrain.

Region
Bridger Range
Location (from list)
The Throne
Observer Name
Dave Zinn
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