21-22

<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>

<p>A few inches of low density snow this morning will not increase the danger, but it will create some small hazards to watch out for. Strong westerly wind will drift any new snow into fresh slabs. These slabs will be shallow, maybe 4” deep, but could be easy for a person to trigger and propagate wide due to weak snow that recently formed near the top of the snowpack (<a href="https://www.mtavalanche.com/images/22/weak-layers-lionhead"><strong>pho…;, <strong><a href="https://www.youtube.com/watch?v=gR0EiO4JEeM&amp;list=PLXu5151nmAvT1nrM2… video</a></strong>, <a href="https://www.youtube.com/watch?v=7pv0tDJMuK4&amp;list=PLXu5151nmAvT1nrM2… video</strong></a>). Fresh drifts will unlikely be large enough to bury a person. If today’s strong wind doesn’t blow the low-density snow back to the sky, it could form thick dangerous slabs in favored, isolated areas. Before riding steep slopes watch for signs of instability like cracking of the snow surface or natural avalanches. Avoid fresh drifts in terrain where any size slide could be deadly due to pushing you into trees or over cliffs.</p>

<p>Avalanches deeper than today’s snow are unlikely, but shouldn’t be ruled out on slopes favored by recent wind-loading. Ian saw this yesterday near Cooke City where he found one slope with a weak layer buried deeper than anywhere else he had found it (<strong><a href="https://www.youtube.com/watch?v=nEC_zOu4JJg">video</a></strong&gt;), and a natural avalanche near Big Sky last Friday shows types of terrain where isolated instabilities might linger (<strong><a href="https://www.mtavalanche.com/node/25668">photo and details</a></strong>).</p>

<p>The forecast for snow has backed off for the mountains near West Yellowstone and the Bridger Range, and less than an inch is expected. It will take a couple inches of new snow for strong wind to form even small fresh drifts. If you choose to ski or ride in avalanche terrain it is always important to carefully assess the snowpack on each slope, only expose one person at a time, and carry proper avalanche rescue gear.</p>

<p>Today the snowpack is generally stable with small and isolated instabilities, and the avalanche danger is LOW. If more snow falls than is expected, danger will rise on wind-loaded slopes.</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>