24-25

<p><span><span><span><strong><span><span>Avalanche danger will be rising</span></span></strong></span></span></span><span><span><span><span><span><span> quickly in the mountains near Island Park that are in the bull’s eye for snowfall today through Monday. I was there </span></span></span></span></span></span><a href="https://youtu.be/4xSA_C9cPuc?feature=shared"><span><span><span><span><s… over a week ago</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>, and we found a widespread weak layer of facets buried about a foot+ deep. Strong southerly winds and heavy snowfall today will make </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> 2 feet deep likey today. Slopes with wind drifted snow will be even more dangerous and avalanches could break even deeper. For these reasons the avalanche danger is CONSIDERABLE.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Now will be a great time to enjoy the snow, but </span></span></span></span></span></span><span><span><span><strong><span><span>take a step back</span></span></strong></span></span></span><span><span><span><span><span><span> today through next week. I would plan on riding in the trees on slopes less than 30 degrees in steepness that aren’t steep enough to slide. As snow accumulates, avoid being underneath all avalanche terrain and any steep slope.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>In the mountains near West Yellowstone, Big Sky, Cooke City, and south of Bozeman, wind-loaded slopes from </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/32638"><span><span><span><span><span><… winds on Tuesday</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span> and today will be the main concern. With a widespread layer of weak facets already buried 1-2 feet deep, the additional stress of a wind slab on top will make persistent slab avalanches likely on these slopes. Non-wind-loaded slopes have much less weight from new snow on them (aka stress), but with such a widespread weak layer, avalanches on these slopes remain possible.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Today the avalanche danger is CONSIDERABLE on wind-loaded slopes. The danger is MODERATE on all others. Regardless of the danger, consider stepping back and dialing down your terrain choices as we enter a period with more snow coming and rising danger. Avalanche conditions will be getting worse before they get better. Fortunately, new snow will make great powder for skiing and riding, and slopes less than 30 degrees in steepness will be the safest option.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The Bridger Range has simply received less snow than other areas and should receive less the next few days (although sometime around Sunday night looks promising). These mountains have a </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/32609"><span><span><span><span><span><… weak layer</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span> as in most of the forecast area that is capable of producing avalanches especially in higher and more exposed terrain with more wind drifting</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>are the main concern mostly on wind-loaded slopes. Human-triggered avalanches are possible and the avalanche danger is MODERATE.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Watch out for </span></span></span></span></span></span><span><span><span><strong><span><span>fresh wind slabs</span></span></strong></span></span></span><span><span><span><span><span><span> that formed as yesterday’s strong southerly winds whipped around the several inches of snow (up to 5” near Cooke) that had fallen over the last four days. </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/32638"><span><span><span><span><span><… person in Hyalite Canyon</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span> south of Bozeman reported strong winds moving snow all day long yesterday, and Big Sky Resort had to close the summit because of strong winds.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>HEADS UP - snowfall early this morning will camouflage these fresh drifts and make them hard to identify.</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> 1-2 ft deep remain possible across the entire forecast area. A weak layer of facets responsible for this problem is very easy to find in the snowpack. The odds of triggering one of these avalanches are higher on slopes loaded by yesterday’s strong southerly winds.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><strong><span><span>Where to travel</span></span></strong></span></span></span><span><span><span><span><span><span> - The easiest option is to seek out slopes less than 30 degrees in steepness that are not steep enough to slide. Otherwise, if getting onto steeper terrain, choose slopes sheltered from yesterday’s strong winds and have a clean runout with no trees, rocks, or terrain traps that make the consequences of an avalanche worse.</span></span></span></span></span></span></p>

<p><span><span><span><strong><span><span>Looking ahead</span></span></strong></span></span></span><span><span><span><span><span><span>, with such a widespread persistent weak layer in the snowpack, the situation will have to get worse before it gets better. More snow coming through this weekend will make persistent slab avalanches more likely and larger, but in the long run can help to bury and heal this weak layer. Be patient and play it safe.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>With two types of avalanches possible today the avalanche danger is MODERATE with heightened avalanche conditions on recently wind loaded slopes</span></span></span></span></span></span></p>

<p>Heightened avalanche conditions exist. Human-triggered <strong>persistent slab </strong>and <strong>wind slab avalanches </strong>are possible. Over the last three days, light snowfall across the advisory area added up to 5” in Cooke City, with a trace to 3” elsewhere. Incremental loading gives us pause but is not likely to increase the avalanche danger outside of specific slopes where drifts of wind-loaded snow are thicker.</p>

<p><strong>Persistent Slab Avalanches:</strong> Persistent weak layers of sugary facets and feathery surface hoar buried 1-2 feet deep (deeper on wind-loaded slopes) sit below a slab of more cohesive snow across much of the advisory area. Observations and recent field videos from <a href="https://www.mtavalanche.com/node/32632"><strong><span>Bacon Rind</span></strong></a>, <a href="https://www.mtavalanche.com/node/32609"><strong><span>north of Bridger Bowl</span></strong></a>, <a href="https://www.mtavalanche.com/node/32605"><strong><span>Lionhead</span></…; and <a href="https://www.mtavalanche.com/node/32585"><strong><span>Cooke City</span></strong></a> all highlight this issue. Recent indicators of persistent slab instability include large collapses on low-angle slopes in Cooke City last weekend (<a href="https://www.mtavalanche.com/node/32603"><strong><span>observation 1</span></strong></a>, <a href="https://www.mtavalanche.com/node/32604"><strong><span>observation 2</span></strong></a>) and multiple natural avalanches that failed on persistent weak layers last week when new and wind-drifted snow loaded slopes. These included several larger slides in <a href="https://www.mtavalanche.com/node/32585"><span>Cooke City</span></a>, a natural avalanche on <a href="https://www.mtavalanche.com/node/32548"><span>Saddle Peak</span></a> and a <a href="https://www.mtavalanche.com/node/32615"><span>chute north of Bridger Bowl</span></a> (go to our <a href="https://www.mtavalanche.com/avalanche-activity"><strong><span>Avalanche Log</span></strong></a> for a full list). Obvious signs of instability, such as avalanches, collapsing and shooting cracks won’t be forthcoming today, but these, along with unstable test results and poor snowpack structure, direct us toward lower-angle terrain.</p>

<p>Recent drifting makes <strong>wind slab avalanches</strong> a hazard on specific terrain features and exacerbates persistent slab instability. Avoid steep, commonly wind-loaded slopes near ridgelines, below cornices and upper-elevation gullies to reduce the likelihood of triggering both wind slab and persistent slab avalanches (<a href="https://www.mtavalanche.com/images/24/cross-loading-henderson-mountain"… 1</span></a>, <a href="https://www.mtavalanche.com/images/24/cross-loading-miller-ridge"><span…;). Visual clues of recent drifting, a stiffening of snow surfaces and shooting cracks are signs of potential instability.</p>

<p>Appropriate terrain selection is the solution to today’s avalanche problems. Selecting slopes less than 30 degrees steep without overhead hazard largely eliminates the risk of avalanches. Along with safe travel practices, good partners, and rescue gear, selecting lower-angle avalanche terrain sheltered from the wind with fewer terrain traps reduces the likelihood and consequences of a slide.</p>

<p>The danger is rated MODERATE.</p>