20-21

<p><strong>WET AVALANCHE DANGER</strong></p>

<p>The sun’s power is intense. Low elevation slopes that get sunshine are melting, getting slushy and becoming quickly unstable. Today's clear skies and unseasonably warm temperatures will also impact high elevation slopes that are sunny. If you are sinking past your ankles in wet snow you are susceptible to triggering or getting caught in a wet avalanche (loose slides at high elevations and wet slabs at lower) and heading out of the backcountry is recommended. You can seek shady, cooler aspects (ie. high, northern facing slopes), but unless you parked your vehicle there, you'll have to navigate wet terrain on your exit. Ian was in Lionhead yesterday and saw first-hand how aspect, elevation and timing affects wet avalanche danger (<a href="https://youtu.be/g8s9PZB134E"><strong><u>video</u></strong></a&gt;). Today I expect many loose wet avalanches as well as cornices sagging and potentially breaking (<a href="https://www.mtavalanche.com/images/21/cornices-along-lionhead-ridge"><s… from Lionhead</u></strong></a>, <a href="https://www.mtavalanche.com/node/24618"><strong><u>Abiathar cornice fall</u></strong></a>). The <strong>wet snow </strong>avalanche danger will start LOW but rise to CONSIDERABLE on all sunny slopes.&nbsp;</p>

<p>On slopes that remain dry the snowpack will be generally stable. There is still weak snow (depth hoar) near the ground and a person would have to be extremely unlucky to trigger an avalanche on this layer. For today the <strong>dry snow</strong> avalanche danger is rated LOW on all slopes.</p>

<p>Yesterday I toured up Sheep Creek north of Cooke City and found a frozen surface on one side of the valley (SW facing) and dry snow on the opposite (NE). I dug on a northeast aspect at 9,000 feet and did not find any weakness, nor did I see any signs of instability (<strong>video</strong>). There might be a rogue wind slab lurking about, but in general it is unlikely someone could trigger an avalanche. These mountains will reach the low 40s F this afternoon and triggering wet avalanches is a possibility, mostly on sunny, lower elevation slopes. For today, the dry snow avalanche danger is rated LOW. The wet snow avalanche danger will start LOW but rise to MODERATE on slopes getting sun. Seeing roller balls, pinwheels or sinking past your ankles in wet snow are signs to head home.</p>

<p>The last large slab avalanches that we know of in the mountains around Bozeman, Big Sky, and West Yellowstone occurred on the last day of February when two different groups triggered slides that broke on sugary depth hoar near the ground, taking out most of the year’s snowpack (<a href="https://mtavalanche.com/weather/wx-avalanche-log"><strong>weather and avalanche log</strong></a>). Since then, skiers and riders have observed small wet, loose snow avalanches on warm sunny days and relatively small wind slab avalanches in recently drifted snow. Yesterday, the Bridger Bowl Ski Patrol noted several natural wet snow avalanches coming out of steep east-facing terrain.</p>

<p>Wet snow avalanche activity is likely to be minimal today and wind slabs are stabilizing. Pay attention to wet, slushy snow deeper than a few inches as a sign of increasing danger this afternoon and to isolated areas where wind-drifted snow may still crack and slide. Small avalanches or cornice fall in technical terrain can be deadly, so stay vigilant with your assessments and safe travel protocols. Watch our recent <a href="https://www.youtube.com/playlist?list=PLXu5151nmAvQDzKmH5K3ZS8Gg3DzwsZ3… from the field</strong></a> to review these avalanche concerns.</p>

<p>We are not forgetting about the weak snow near the ground. It will return to the forefront of the conversation when melt-water penetrates deep into the snowpack or if significant spring snowstorms arrive, but for now, triggering an avalanche on this layer is unlikely. The avalanche danger is LOW.</p>

<p>It may not have snowed in Cooke City as forecast, but at least it got windy. For several hours last night 15-25 mph wind transported the remaining soft snow into drifts that could crack and avalanche today. Wind-slabs are likely to be small and on isolated terrain features but could cause significant problems in high consequence terrain. Recent cornice collapses near Abiathar and Mount Fox remind us to minimize time spent under these overhanging masses of snow (<a href="https://www.mtavalanche.com/node/24618"><strong>details</strong></a&gt;). Cooler temperatures and cloudy skies will limit warming today but keep wet, loose snow avalanches in mind if the sun pops out this afternoon. Generally safe avalanche conditions exist in Cooke City and the danger is LOW.</p>

<p>If you get out, please send us your observations no matter how brief. You can submit them via our <a href="https://www.mtavalanche.com/node/add/snow_observation"><strong>website<…;, email (<a href="mailto:mtavalanche@gmail.com"><strong>mtavalanche@gmail.com</strong></a…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>

<p>Several isolated avalanche concerns remain in the mountains around Bozeman, Big Sky, and West Yellowstone. Small wind-slabs or drifts of snow can avalanche under the weight of a skier or rider. Yesterday, my partner and I saw these in the Northern Bridger Range, skiers noted them around Beehive Peak, and the Big Sky Ski Patrol triggered a slab that broke up to 18” deep during avalanche mitigation work. These avalanches are likely too small to bury someone but would be dangerous in extreme or technical terrain.</p>

<p>Water in the snowpack on slopes getting baked by the sun on warm days causes the snow to lose cohesion and slide downhill. If you sink deeper than mid-boot level into wet or slushy snow, move to a shadier aspect, a higher elevation, or call it a day. As I outlined in my <a href="https://youtu.be/HCjetG0dr0I"><strong>video</strong></a&gt; from the Northern Bridgers yesterday and Ian showed in <a href="https://www.youtube.com/watch?v=l5LfdUsd0Wk"><strong>Specimen creek</strong></a> last week, these are often aspect and elevation-driven events. Increasing cloud cover will minimize this danger today.</p>

<p>Finally, I had a stability test fail near the ground yesterday (<a href="https://mtavalanche.com/images/21/frazier-basin-profile-14-march"><stro… profile</strong></a>) and Doug had a massive slab fall in his lap in <a href="https://www.youtube.com/watch?v=8Q4gTjESoq0"><strong>Tepee Basin</strong></a> last week. Large avalanches failing on weak snow near the ground are unlikely but we cannot put these deeply buried weak layers out of our mind. Assess the snowpack and rigorously follow standard safe travel practices.</p>

<p>Human-triggered avalanches are unlikely and the danger is rated LOW.</p>

<p>Generally, safe avalanche conditions exist in Cooke City. If you are considering more adventurous terrain selection, keep a few things in mind. Small slab avalanches (<a href="https://www.mtavalanche.com/images/21/meridian-peak-avalanche"><strong>…;, <a href="https://www.mtavalanche.com/images/21/storm-slab-cooke-city"><strong>ph…;, <a href="https://www.youtube.com/watch?v=fRcnpNGTKCQ&amp;list=PLXu5151nmAvQDzKmH…;) and loose, wet snow avalanches if it warms up and stays sunny (<a href="https://www.mtavalanche.com/images/21/skier-triggered-loose-snow-slide-…;) can have severe consequences in steep terrain. Skiers and riders have encountered both of these isolated issues within the last week. Large cornices have collapsed recently. A group climbing a couloir on Abiathar was nearly hit by vehicle-sized chunks “raining down” on them (<a href="https://www.mtavalanche.com/node/24618"><strong>details</strong></a&gt;). Skiers also observed a recent cornice collapse on Mount Fox. Avalanches are unlikely today and the danger is rated LOW.</p>

<p>If you get out, please send us your observations no matter how brief. You can submit them via our <a href="https://www.mtavalanche.com/node/add/snow_observation"><strong>website<…;, email (<a href="mailto:mtavalanche@gmail.com"><strong>mtavalanche@gmail.com</strong></a…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>