Mar 9. We rode out Lionhead Ridge... there were two or three shallow small wind slabs below Lionhead Ridge. Photo: GNFAC
Mar 9. We rode out Lionhead Ridge... there were two or three shallow small wind slabs below Lionhead Ridge. Photo: GNFAC
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.
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.
Somewhat fresh looking slab avalanche in upper Storm Castle Creek on an East facing slope. Looks like there might be a wet loose slide to the right of it as well. One small wet loose avalanche, probably from yesterday, in Maid of the Mist bowl.
Widespread wind effect in the alpine of Hyalite yesterday. The windslabs were fairly stubborn however, and were only breaking in very small pockets, not propagating outwards. Where the recent snow was still protected from sun and wind, large dry loose slides were easy to trigger.
<p><span><span><span><span><span><span>Today the primary avalanche problem is </span></span></span></span></span></span><span><span><span><strong><span><span>wind slab avalanches</span></span></strong></span></span></span><span><span><span><span><span><span> where 5-7” of snow from Thursday was drifted into stiffer slabs. These drifts were reactive and easily triggered the last couple days. Yesterday in the northern Bridgers skiers triggered a few wind slabs that were 8-10” deep and 10-20’ wide. One person was 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>). Two days ago Ian and I found similar fresh drifts that easily cracked under our skis (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/25/reactive-wind-slabs"><span><span>…;, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/25/reactive-wind-slabs-2"><span><spa…;, </span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=Y8xb7L0c0Ug"><span><span><span><strong>…;
<p><span><span><span><span><span><span>Above freezing temperatures and sunny skies will make </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> a concern later in the day. These will probably be small, but could easily knock over a person. Watch and feel for a wet or moist snow surface to indicate you could trigger shallow loose snow slides, and anticipate this hazard to develop mostly around rock outcrops on slopes that receive direct sunshine. </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Remain cautious of travel on steep wind-loaded slopes and steep sunny slopes today, especially above cliffs, rocks or thick trees where even a smaller slide would be more dangerous.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Near West Yellowstone and the southern Madison and Gallatin ranges an additional 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 buried in late January. The last of these deeper avalanches were over a week ago (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/25/wind-loaded-slide-backside-lionhe…;). The likelihood has decreased, but the size would be big enough to have serious consequences. These slides were mostly on mid-elevation slopes with trees around and have surprised riders, leading to several 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><span><span><span><span><span><span>Travel one person at a time across steep slopes and have a partner watching from a safe spot. If you ride steeper slopes, choose terrain with minimal trees, rocks, cliffs or confined gullies. </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>The avalanche danger is MODERATE.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Cooke City got less new snow last week, so the likelihood and size of potential avalanches is smaller. </span></span></span></span></span></span><span><span><span><strong><span><span>Wind slab avalanches</span></span></strong></span></span></span><span><span><span><span><span><span> and </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> are a concern, but their size will be small and distribution is minimal. Avalanches breaking deeper on buried weak layers are unlikely. The last of these persistent slab avalanches were a couple weeks ago (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34382"><span><span><span><span><span><…;), and were the only slides of this type near Cooke City over the last couple months.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>While the snowpack is generally stable, you should follow standard safe protocols for travel in avalanche terrain. Expose only one person at a time to steep slopes and carry proper rescue gear (transceiver, probe and shovel). Stay alert for recent drifts and wet loose avalanches, especially in terrain where a small slide has higher consequences. </span></span></span></span></span></span><span><span><span><span><span><span>The avalanche danger is LOW near Cooke City.</span></span></span></span></span></span></p>
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From obs: "Skier triggered wind slab on Northeast slope at 7,450 feet elevation. One skier was caught and carried roughly 10 feet before the slide came to a stop."
We also received reports from another group (IG story video) that triggered a couple similar sized wind slab avalanches in north facing chutes in Frazier Basin.
