This natural wet, loose avalanche on the east face of Baldy Mtn in the Bridger Range likely released on March 27. Photo: B. Finch
Skiers noted wet slab and wet loose avalanche activity on March 28th in the mountains near Cooke City. Photo taken March 30. Photo: B. Fredlund
Skiers noted wet slab and wet loose avalanche activity on March 28th in the mountains near Cooke City. Photo was taken March 30. Photo: B. Fredlund
<p>Temperatures have mostly remained under 32 degrees F for the last 24 hours, creating a thick crust on top of the snowpack and improving stability in the mountains around Bozeman, Big Sky and West Yellowstone. In Beehive Basin yesterday, this crust was 3-4” thick and supportable on skis (<a href="https://www.youtube.com/watch?v=O5K_gNFeBt8"><strong>video</strong></a&…;). This morning, avalanches will be unlikely on any slope with a thick, supportable melt-freeze crust. However, this crust will quickly break down with the trifecta of warm temperatures, blazing spring sun and light winds forecast for the day. As I noted in Beehive, the snowpack is isothermal, meaning it is very close to its melting point of 32 degrees for its entire depth. Therefore, when the melt begins, it will go fast and wet loose avalanches in the upper snowpack are likely and larger, more destructive wet slab avalanches possible.</p>
<p>Get on the snow early while it is still cold and get out of avalanche terrain before the crust breaks down. Remember that lower elevations will heat up and destabilize earlier. Don’t get yourself trapped on a high elevation north-facing run with no good options for getting home.</p>
<p>Look to this weekend for examples of wet snow avalanche activity, such as the cycle in the Bridger Range (<a href="https://www.mtavalanche.com/node/26363"><strong>photos and details 1</strong></a><strong>,</strong> <a href="https://www.mtavalanche.com/node/26364"><strong>2</strong></a><strong>, </strong><a href="https://www.mtavalanche.com/node/26365"><strong>3</strong></a>) and wet snow avalanches at the Yellowstone Club that buried a road (<a href="https://www.mtavalanche.com/node/26377"><strong>photos and details</strong></a>).</p>
<p>Today, the danger will begin at LOW and increase to CONSIDERABLE as the day warms. </p>
<p>The temperature at the Lulu Pass weather station near Cooke City is 8 degrees F this morning. This is a significant change from the preceding week of warm temperatures that resulted in many wet snow avalanches (<a href="https://www.mtavalanche.com/avalanche-activity"><strong>avalanche activity log</strong></a>). This morning avalanches are unlikely due to a thick melt-freeze crust formed at the snowpack’s surface. As the day warms up into the low 40s under sunny skies, this crust will break down and avalanches will be possible. In his <a href="https://www.youtube.com/watch?v=8LbaFYKHIvE"><strong>video</strong></a&…; yesterday, Alex dug into the snowpack in Cooke City and noted that meltwater affected the weak layer of facets 1-3’ under the surface. This will likely make the layer less reactive until it becomes saturated again, but it is worth digging and testing if you plan to get into steep terrain.</p>
<p>Today the danger will start as LOW and increase to MODERATE as the day warms up and the surface crust breaks down. </p>
<p>If you get out, please send us your observations no matter how brief. You can submit them via our website, email (mtavalanche@gmail.com), phone (406-587-6984), or Instagram (#gnfacobs).</p>
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I dug a pit at 9,300' on a SW facing slope close to the Sawtelle Road. The snow was wet and has lost a lot of strength. I was breaking through a 2" frozen crust at the surface into wet, mushy snow. Once the crust breaks down I expect wet avalanches to continue. The snowpack is 6' deep, very thin for this time of year. Water was able to penetrate this depth quickly. Be careful traveling later in the day when the crust begins to melt and you sink far. This is a sign of instability.
<p>Our level of uncertainty about the avalanche danger is relatively high today. A week of above freezing temperatures weakened the snowpack structure. Last night, elevations above 8000’ experienced below-freezing temperatures which is good for stability. This morning, precipitation started as rain in the Bridger Range before turning to snow. As the storm spreads south, rain will make your day less fun and further saturate and destabilize the snowpack. Conversely, slopes with a thick melt-freeze crust formed by cooler temperatures are more stable. Avoid avalanche terrain if you are breaking through the crust into unconsolidated wet snow remembering that the snowpack is less stable at lower elevations. As I noted from the Bridger Range yesterday, today is “<a href="https://www.youtube.com/watch?v=Fk9evguplag"><strong>Not your normal powder day</strong></a>.”</p>
<p>To understand how weak the snowpack got with the warm temperatures visit the <a href="https://www.mtavalanche.com/avalanche-activity"><strong>avalanche activity log</strong></a>. There are fourteen entries from the last three days. A few highlights include a natural avalanche cycle in the Bridger Range (<a href="https://www.mtavalanche.com/node/26363"><strong>photos and details 1</strong></a><strong>,</strong> <a href="https://www.mtavalanche.com/node/26364"><strong>2</strong></a><strong>, </strong><a href="https://www.mtavalanche.com/node/26365"><strong>3</strong></a>), wet snow avalanches intentionally triggered by the YCSP that buried a road (<a href="https://www.mtavalanche.com/node/26377"><strong>photos and details</strong></a>) and widespread terrain closures and natural inbounds avalanches at Big Sky, Bridger and Yellowstone Club (<a href="https://www.mtavalanche.com/node/26375"><strong>photos and details</strong></a>).</p>
<p>Careful snowpack evaluation, cautious route-finding and conservative decision-making are essential. The danger is CONSIDERABLE due to large variation between slopes at different elevations and a higher than normal level of uncertainty.</p>
<p>Temperatures in the higher elevations in the mountains around Cooke City dropped to the mid 20s F last night and are forecast to drop into the low 20s F by early afternoon. Lower elevations that didn’t get as cold are suspect for wet snow avalanches if you are breaking into unconsolidated wet snow.</p>
<p>The high peaks did not escape the warmup without a wet avalanche cycle. Alex took photos of a couple of larger wet slab avalanches (<a href="https://www.mtavalanche.com/images/22/wet-slab-south-silver-gate"><stro…;) and many loose snow avalanches (<a href="https://www.mtavalanche.com/images/22/wet-slides-peak-9595-near-ynp"><s…;) on his drive into Cooke City Sunday. Skiers captured some excellent images of yesterday’s avalanche activity (<a href="https://www.mtavalanche.com/node/26382"><strong>photos and details</strong></a>). Avoid steep slopes with unsupportable wet snow and on all others dig down to assess the snowpack for a persistent weak layer of facets under 1-3’ of snow that has resulted in recent avalanches including one that caught three skiers last Thursday (<a href="https://www.mtavalanche.com/node/26321"><strong>video, photos & details</strong></a>).</p>
<p>Human-triggered avalanches are possible in the mountains around Cooke City where the danger is rated MODERATE.</p>
<p>If you get out, please send us your observations no matter how brief. You can submit them via our website, email (mtavalanche@gmail.com), phone (406-587-6984), or Instagram (#gnfacobs).</p>
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