GNFAC Avalanche Forecast for Tue Mar 11, 2025
<p><span><span><span><span><span><span>Avalanches are unlikely throughout the forecast area. While conditions are stable overall, isolated instabilities may exist within recently drifted snow and the warming snow later this afternoon. Weak layers in the mountains around West Yellowstone are dormant until the next storm wakes them up. </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Most recent wind drifts have bonded to underlying snow surfaces, and slides will be relatively small on isolated slopes where </span></span></span></span></span></span><span><span><span><strong><span><span>wind slab instability</span></span></strong></span></span></span><span><span><span><span><span><span> exists. The most likely location for lingering instability is upper-elevation terrain, especially on slopes immediately below cornices (cornices collapsing under their weight is a separate but relevant concern). Dig an extended column test a couple of feet deep to assess the snowpack and watch for cracking around your skis, board or sled if you are considering travel on steep and consequential slopes where a small avalanche could be dangerous (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=e2-26tmDdIc&embeds_referring_euri=h…;
<p><span><span><span><span><span><span>Small, </span></span></span></span></span></span><span><span><span><strong><span><span>wet loose avalanches</span></span></strong></span></span></span><span><span><span><span><span><span> may release naturally or with human triggers as the day warms, especially in south-facing and rocky terrain where melting weakens snow surfaces. Multiple days of sequential melting and freezing, along with breezy conditions this afternoon, should limit instability. Watch for cinnamon roll-like pinwheels and wet snow in the top few inches of the snowpack that indicate decreasing stability. Move to shadier, north-facing terrain to resolve the issue. </span></span></span></span></span></span></p>
<p><span><span><span><strong><span><span>Persistent slab avalanches</span></span></strong></span></span></span><span><span><span><span><span><span> failing 2-3’ deep on buried weak layers are unlikely, with the last slide of this type occurring a week and a half ago (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34428"><span><span><span><span><span><…;). These weak layers are primarily limited to the </span></span></span></span></span></span><span><span><span><strong><span><span>Lionhead area, Southern Gallatin, and Southern Madison Ranges</span></span></strong></span></span></span><span><span><span><span><span><span>. Dig three feet and test for instability on weak layers to further reduce the chances of getting unlucky (</span></span></span></span></span></span><a href="https://youtube.com/shorts/q0IGs0dKpQU?feature=share"><span><span><span… Mark’s video</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span> about finding this layer). Alex described in his </span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=2T1mh47gpro"><span><span><span><strong>… video</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span> from Lionhead why persistent weak layers in the mountains near West Yellowstone will return as a concern when they get loaded by the weight of new snow. </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Remember that experts are simply people who execute the basics flawlessly. Adhere to the fundamentals of avalanche safety–beacon, shovel, probe, one at a time on steep slopes and eyes open for signs of isolated instability. The danger is rated LOW. </span></span></span></span></span></span></p>
Upcoming Avalanche Education and Events
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GNFAC Avalanche Forecast for Mon Mar 10, 2025
<p><span><span><span><span><span><span>In the Lionhead area and the Southern Gallatin and Southern Madison Ranges, smaller avalanches on slopes with recent drifts of wind-loaded snow and larger avalanches breaking on buried weak layers are possible. </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>The primary concern is </span></span></span></span></span></span><span><span><span><strong><span><span>persistent slab avalanches</span></span></strong></span></span></span><span><span><span><span><span><span> breaking 2-3’ deep on weak layers formed in late January. The last avalanches failing on these weak layers occurred over a week ago and triggering one has become less likely. These slides mostly failed on treed, mid-elevation slopes, leading to several burials and close calls (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34421"><span><span><span><strong><span…;, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34413"><span><span><span><strong><span… Creek</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34341"><span><span><span><strong><span… Basin</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Yesterday, Alex rode through the Lionhead area and described in his </span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=2T1mh47gpro"><span><span><span><strong>…; why the snowpack structure remains a concern. </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>will be smaller, generally breaking less than a foot deep, and suspect terrain at upper elevations and below cornices is identifiable. Avoid these specific areas or watch for indicators of instability, such as shooting cracks. </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Carry and train with rescue equipment and ensure only one person at a time is exposed to terrain steeper than 30 degrees. Consider the potential outcomes of an avalanche on a given slope and avoid those with higher consequence features such as trees, cliffs and gullies. The danger is rated MODERATE</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>The snowpack is generally stable in the mountains around Bozeman, Big Sky, Cooke City and Island Park. Small avalanches are possible on slopes with isolated instability related to recently wind-drifted snow. Cooler temperatures and cloud cover will limit wet loose avalanches. </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Yesterday, I toured Hyalite Canyon and assessed for </span></span></span></span></span></span><span><span><span><strong><span><span>wind slab</span></span></strong></span></span></span><span><span><span><span><span><span> </span></span></span></span></span></span><span><span><span><strong><span><span>instability </span></span></strong></span></span></span><span><span><span><span><span><span>by digging extended column tests and watching for shooting cracks. I found that wind drifts have generally stabilized (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34555"><span><span><span><span><span><…;). The primary concern resides in the isolated areas where they have not bonded. Two days ago, skiers in the Bridger Range triggered wind slabs 8-10” deep and 10-20’ wide, with one person caught and carried ten feet (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34550"><span><span><span><strong><span… and photos</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Some people are choosing to ski and ride in very steep and technical terrain. While this is a reasonable time to consider more committing objectives, the margin for error is razor-thin in these spaces, with slight miscalculations (avalanches) having significant consequences. Assess the snowpack for isolated instability in this terrain and back off if conditions don’t feel right (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=e2-26tmDdIc&embeds_referring_euri=h…;
<p><span><span><span><span><span><span>While most slopes are stable, the fundamentals of safe travel in avalanche terrain always apply–beacon, shovel, probe and one at a time on steep slopes. The avalanche danger is LOW.</span></span></span></span></span></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
Weather and Avalanche Log for Mon Mar 10, 2025
Temperatures in Bridgers above freezing
recent small wind slabs at Lionhead
We rode out Lionhead Ridge and around the north end to the head of Targhee Creek. Skies started overcast, but cleared through the day as wind calmed from moderate to light out of the west and southwest.... there were two or three shallow small wind slabs below Lionhead Ridge.
Mar 9. We rode out Lionhead Ridge... there were two or three shallow small wind slabs below Lionhead Ridge. Photo: GNFAC
Forecast link: GNFAC Avalanche Forecast for Tue Mar 11, 2025
Mar 9. We rode out Lionhead Ridge... there were two or three shallow small wind slabs below Lionhead Ridge. Photo: GNFAC
Forecast link: GNFAC Avalanche Forecast for Mon Mar 10, 2025GNFAC Avalanche Forecast for Tue Mar 11, 2025
Still finding poor structure, recent small wind slabs
We rode out Lionhead Ridge and around the north end to the head of Targhee Creek. Skies started overcast, but cleared through the day as wind calmed from moderate to light out of the west and southwest.
There were zero recent large persistent slab avalanches, and there were two or three shallow small wind slabs below Lionhead Ridge. The snow surface became moist, but crusts from previous warm days and cold night only softened slightly. There was very little, if any, wet snow avalanche hazard today.
We dug at the top of Lionhead Ridge on the south side of Airplane Bowl. 9,300', NE aspect. There was a 2.5' deep very hard slab (1f to P+) above soft facets (4F-), snow depth of 5 feet. We had ECTX, but with extra hits and some removal of the slab it propagated with a clean break. The persistent slab avalanche problem is becoming more stubborn, but not going away. For now it is not likely, but there is probably an isolated slope where you could trigger an avalanche, and we could see this problem arise again with more snow next week.
Generally Stable Conditions
We skied to Flanders Mountain, traversed the ridgeline, and dropped into the northwest-facing terrain near the Winter Dance Buttress down to the Main Fork. Ridgelines had moderate to strong winds but minimal transport as snow at upper elevations had already moved or had hardened with recent wind and warm temperatures. Wind Slabs that we assessed were stubborn to unreactive, but there is probably one out there that could result in a small avalanche. No signs of dry snow instability during the tour or in our snowpack assessments (Flanders Bowl - ECTN Teens and 20s and Near Winter Dance Buttress - ECTN Teens and 20s). Snow surfaces were warming (wetting) in south-facing terrain and on all aspects below 8000' by 3 PM. However, we did not see any natural wet snow activity.
I would be watching out for isolated wind slab instability and wet loose avalanches for now.