A snowobarder tagged us in an IG story of triggering a long running, powerful wet loose slide in the Bridger Range.
We went on a tour in the Bridgers today, we ascended the east ridge of Naya Nuki to the entrance of the Great One. Wind was blowing and we were being careful about potential wind slabs up high.
Skier 1 ski cut the top of the chute and produced a small wind slab that ran to the break in the chute and continued another 100 vert down the east apron. After all meeting up halfway down, skier 2 proceeded to ski the E facing apron. A wind slab propagated and carried skier 2 roughly 300 vert down the apron where skier 2 was able to swim out of the fall line and came to a rest on top of the debris. Everyone was okay aside two missing ski poles.
On the way out, we saw a few more small natural wind slabs that broke naturally near ridge lines as well as point and release wet slides.
From BBSP: " At 2.45?pm a... solo skier triggered a wind loaded pocket on the main face of Saddle Peak that ran down over the cliff and produced an impressive powder cloud.... I met him... and confirm he was alone and no one was in front of him. The avalanche looked to be 2' deep on the southern flank and 5" deep on the northern flank... It entrained more snow on the way down, one 2' deep downhill wind loaded pocket and some loose wet snow. It ran into the bottom of the going home chute, gouging a large hole and then 100ft downhill left a 200ft by 30ft wide shallow debris pile."
Observed multiple D1-1.5 natural dry loose avalanches (and some tiny wind slab pockets under the ridge cornice) that likely occurred during peak warming around 2-3 PM. North/sheltered aspects from ~9- 8.5k held an average of 8+ inches of dry, drifted snow. Early AM to mid-afternoon, very active wind transport followed by tapered winds and a rapid increase in temp. Also observed one small wind slab occurring between Saddle & the Football Field, possibly skier-triggered.
<p><span><span><span><span><span><span>Wet snow is back to the top of our list of concerns. Most sunny slopes will have a thin crust at the surface this morning that will break down as the day heats up. As the crust melts and the softer snow underneath gets wet, expect to see and trigger </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>. These slides could break at your feet, or come down from rocky areas above you. Do not discount the danger of these slides. With plenty of soft snow from the last week, these wet loose avalanches could get pretty big. With firm crusts underneath the recent snow, they will also run long distances. Look for a wet snow surface and roller balls rolling down the hill as your indications that it’s time to get off steep, sunny slopes. The peak instability will be late this afternoon, after slopes have baked for hours in intense April sunshine.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>You might also still be able to find an isolated </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> that could still avalanche. Most of these will be well bonded at this point, but do be on the lookout for unstable drifts on high elevation shady slopes, particularly those above cliffs or rocks where even a small slide would have big consequences. </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>The avalanche danger will start off LOW this morning and quickly rise to MODERATE as the day heats up and it becomes possible to trigger large avalanches.</span></span></span></span></span></span></p>
Wind slab near Cooke City from yesterday. Intentionally triggered. North aspect, 10,100'. 1' deep, 20' wide. Photo: B Fredlund
<p><span><span><span><span><span><span>Today’s transition between colder, snowy weather and warm, sunny, springlike weather bring a range of concerns.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>While winds have generally been light, </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> are a concern in places where winds have drifted and slightly stiffened the recent snow. Look for these drifts below cornices and near ridgelines. With east winds in the Bridger Range, there may be drifts in some unusual locations, so be particularly watchful there. Over the last couple days, thin, relatively small, wind slabs have been reported in the </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34832"><span><span><span><span><span><… Range</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34824"><span><span><span><span><span><… Basin</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>, and the </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34826"><span><span><span><span><span><… around Cooke City</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>. Looking for wind textured surfaces and avoiding drifts is the easiest way to deal with this problem. </span></span></span></span></span></span></p>
<p><span><span><span><strong><span><span>Dry loose avalanches </span></span></strong></span></span></span><span><span><span><span><span><span>(sluffs) can pack a surprising punch and there is plenty of soft snow for them to entrain. Don’t underestimate their power if you’re getting onto steeper slopes. </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>As soon as direct sunshine hits slopes today </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>will become the big player. Today will be the first time the recent snow gets wet. This initial wetting is often the peak of instability for wet loose avalanches. With lots of recent snow, these could be quite big slides and they’ll run a long way on last week’s crusts.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Temperatures are warmer and it’s going to be sunnier around West Yellowstone, Island Park, and Cooke City this morning, so the onset of these wet loose slides will be earlier in those places. Near Bozeman and Big Sky, there is more new snow but temperatures are cooler and clouds should stick around for longer, so it’ll take longer for things to get going, but once they do, we could see bigger avalanches.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Be on alert as soon as the sun is not blocked by clouds. The snow surface getting sticky and wet and rollerballs rolling down hill are your clues that it’s time to move to shadier or less steep slopes. </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>With a range of concerns to watch for and large avalanches possible, the avalanche danger is MODERATE today.</span></span></span></span></span></span></p>
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