21-22

<p>In the last two days, 6-10” of low-density snow equal to 0.3-0.7” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/null/?cid=nrcseprd1314… water equivalent</a> (SWE) fell onto a variety of weak layers within the top 18” of the snowpack in the Bridger, Madison and Gallatin Ranges. The new snow will not be enough to tip the scales toward widespread instability. Consider recent avalanche activity to understand the concerns for the day. On the less likely end of this spectrum was a shallow but wide avalanche of hard windblown snow on Saddle Peak that occurred on January 25th (<a href="https://mtavalanche.com/node/25629"><strong>details, photos and video</strong></a>) and on the more likely end was a windslab triggered near Big Sky by a cornice collapse on Friday (<a href="https://mtavalanche.com/node/25668"><strong>details and photo</strong></a>) and small loose snow avalanches south of Bridger Bowl last Thursday (<a href="https://mtavalanche.com/node/25644"><strong>details and photo</strong></a>). Today, slab avalanches could be large enough to injure or bury a skier or rider and loose snow avalanches could result in an unpleasant tumble in technical terrain.</p>

<p>Dig down a couple of feet and perform a quick stability test to assess the upper levels of the snowpack before skiing and riding any steep slope (<a href="https://www.youtube.com/watch?v=sqn0KFZqXYs&amp;list=PLXu5151nmAvSpq8Ps… to test in less than 1-minute</strong></a>). If you don’t see signs of instability during your travel or in your stability test, stay warm and enjoy the new snow.</p>

<p>Today, human-triggered avalanches are possible and the danger is MODERATE.&nbsp;</p>

<p>The mountains around West Yellowstone and Cooke City picked up 4-5” of snow equal to 0.2-0.3” of SWE. This will soften the surface but will not significantly increase the avalanche danger. Yesterday in Cooke City, Doug noted that new snow was falling on weak facets at or near the surface and he would not be surprised if folks started triggering slides <em>if</em> the snow kept up (<a href="https://www.youtube.com/watch?v=6aMGx0KCKFU"><strong>video</strong></a&…;). Well, fortunately for stability and unfortunately for riding and skiing conditions, the snow did <em>not</em> keep up. Dig a snowpit to assess the top couple of feet of the snowpack and watch for signs of isolated instability as you travel. Pull back if you find localized areas with weaker snow. The fundamentals don’t change with the avalanche danger rating. Carry and be familiar with avalanche rescue gear and expose only one person at a time to avalanche terrain.</p>

<p>Human-triggered avalanches are unlikely and the danger&nbsp;is LOW.&nbsp;</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>The mountains around Big Sky and Bozeman received 5” of low-density snow equal to 0.3” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/null/?cid=nrcseprd1314… water equivalent</a> (SWE). The wind is transporting this snow into soft slabs where triggering an avalanche is possible. Small, loose snow avalanches on non-wind-loaded slopes will be relatively harmless except in technical terrain where they could be large enough to push you into or off obstacles.</p>

<p>Yesterday, the Big Sky Ski Patrol triggered isolated soft slabs up to 6” deep and loose snow avalanches. Expect more of the same especially as more new snow comes in today. Prior to yesterday’s storm, we observed weak snow at or near the surface across much of the advisory area. This weak layer resulted in a 1000’ wide avalanche and long-running loose snow sluffs on Saddle Peak one week ago (<a href="https://www.youtube.com/watch?v=SAKP0a0G9ks&amp;list=PLXu5151nmAvT1nrM2…; </strong>and <a href="https://mtavalanche.com/node/25629"><strong>details</strong></a&gt;). A natural avalanche near Big Sky last Friday is another example of wind-loaded terrain where instabilities are more likely (<a href="https://www.mtavalanche.com/node/25668"><strong>photo and details</strong></a>). Avalanches breaking deeply in the snowpack are unlikely, but it is worth assessing for isolated areas of instability. As Ian and Doug recently found, the entire snowpack in some of the lower elevation, shallower ski destinations got weaker during January’s high pressure (<a href="https://www.youtube.com/watch?v=VjIW7Pp-hz0&amp;list=PLXu5151nmAvT1nrM2… Ellis Video</strong></a><strong>, </strong><a href="https://www.youtube.com/watch?v=6ax6l1PhUb0&amp;list=PLXu5151nmAvT1nrM2… Mountain Video</strong></a>).</p>

<p>Avoid steep slopes if you observe signs of instability such as recent avalanche activity, shooting cracks or fresh drifts of wind-blown snow. The danger is MODERATE on wind-loaded slopes and LOW on all others.</p>

<p>The southern ranges of the advisory area received 2-3” of light snow equal to 0.1 to 0.2” of SWE. Watch for signs of isolated instability especially at higher elevations or in wind-prone areas where small drifts could crack and avalanche. Any avalanche will likely be less than 6” deep except in isolated areas where recent weak layers enhance the danger as Ian explained from Cooke City last weekend (<a href="https://www.youtube.com/watch?v=nEC_zOu4JJg"><strong>video</strong></a&…;). While weak layers at or near the snowpack surface are widespread across the southern portions of the advisory area, they will not be a widespread <em>avalanche concern</em> until they get loaded by more snow (<a href="https://www.mtavalanche.com/images/22/weak-layers-lionhead"><strong>pho…;, <a href="https://www.youtube.com/watch?v=gR0EiO4JEeM&amp;list=PLXu5151nmAvT1nrM2… video</strong></a>, <a href="https://www.youtube.com/watch?v=7pv0tDJMuK4&amp;list=PLXu5151nmAvT1nrM2… video</strong></a>).</p>

<p>If you are traveling through avalanche terrain, assess the snowpack, limit exposure to one person at a time on steep slopes and be well practiced with the rescue equipment you carry.</p>

<p>Large, human-triggered avalanches are unlikely 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>