21-22

<p>The Northern Gallatin Range was the snowfall winner yesterday with 6” of snow equal to 0.4” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/null/?cid=nrcseprd1314… water equivalent</a> (SWE). The Southern Gallatin and Southern Madison Ranges and mountains around Cooke City got 2-3” equal to 0.1-0.2” SWE. The wind will pick up through the day and easily move this low-density snow into small drifts where human-triggered avalanches are possible. In the mountains around Cooke City and in the Southern Gallatin and Southern Madison Ranges there is a thin weak layer buried under one to two feet of snow on many slopes that may result in wider propagation of these wind slabs (<a href="https://www.youtube.com/watch?v=I6AleixLxTI&amp;list=PLXu5151nmAvT1nrM2…;, <a href="https://www.mtavalanche.com/images/22/surface-hoar-layer-s-madison-rang… </strong></a><a href="https://www.mtavalanche.com/images/22/surface-hoar-layer-s-madison-rang… surface hoar</strong></a>). A skier triggered avalanche late last week near Cooke City and one reportedly triggered on Sunday near Goose Lake illustrate the type and size of avalanche that are possible today (<a href="http://www.mtavalanche.com/node/25595"><strong>photo and details</strong></a>).</p>

<p>Avalanches breaking on deeper weak layers are unlikely so spend your time <a href="https://www.youtube.com/watch?v=sqn0KFZqXYs&amp;list=PLXu5151nmAvSpq8Ps… quick pits </strong></a>to test interfaces in the upper snowpack. If you observe propagating tests or see obvious signs of instability such as shooting cracks or recent avalanches, retreat to a different slope or move out of wind-loaded terrain. The danger is MODERATE on wind-loaded slopes and LOW on all others.</p>

<p>In the Lionhead area along with the Bridger and Northern Madison Ranges 2-3” of snow equal to 0.1-0.2” of SWE fell on a mostly stable snowpack. A weak layer of surface hoar is buried under 6” of light snow near West Yellowstone, but similar to areas without the weak layer, this is not enough to pose much of a hazard outside of technical or very steep terrain where a small avalanche could push you into or off obstacles. Over the weekend, the wind blew recent snow into relatively small, but unstable drifts in the northern ranges. On Saturday, a snowmobiler in the northern Bridger Range triggered a slide on a small slope (<a href="https://www.mtavalanche.com/images/22/snowmobile-triggered-wind-slab-sm…;) and on Sunday, a skier north of Bridger Bowl was caught and carried about 150’ in a small avalanche (<a href="https://mtavalanche.com/node/25615"><strong>details and photos</strong></a>). Thankfully, all parties involved were unharmed. Winds have been calm since then and these wind slabs have largely stabilized.</p>

<p>Today, avalanches are unlikely. Dig and test the upper snowpack and watch for signs of isolated instability such as cracking and expose only one person at a time to avalanche terrain. With mostly stable conditions, 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>Yesterday, the wind blew 20-30 mph in the Southern Gallatin and Southern Madison Ranges and the mountains around Cooke City and created 1-2’ drifts of snow on top of a weak layer of buried surface hoar. Human triggered avalanches are possible on slopes where recent drifts of snow and this weak layer overlap. Avalanches are unlikely on slopes missing one of these two ingredients, as Alex and Ian observed in the Taylor Fork prior to yesterday’s wind (<a href="https://www.youtube.com/watch?v=I6AleixLxTI&amp;list=PLXu5151nmAvT1nrM2…;). Triggered by a group of skiers on Friday, a shallow slide that propagated across a steep couloir near Cooke City indicates of the type of avalanche you could trigger today (<a href="http://www.mtavalanche.com/node/25595"><strong>photo and details</strong></a>). Luckily, the skiers were sheltered from the slide and were unharmed.</p>

<p>Indicators of instability such as recent avalanches or cracks shooting from your skis, board or sled are clear signs that you found the unstable combo and should retreat. If signs of instability aren’t as obvious, dig down to look for the <a href="https://www.mtavalanche.com/images/22/surface-hoar-layer-s-madison-rang… surface hoar</strong></a> and perform a quick stability test before entering steep terrain. Avalanches breaking on deeper weak layers are unlikely.</p>

<p>The danger is MODERATE on wind-loaded slopes and LOW on non-wind loaded slopes.</p>

<p>Dangerous, human-triggered avalanches are unlikely in the mountains around Bozeman, Big Sky and West Yellowstone. A weak layer of feathery surface hoar is buried under 6” of snow in the Lionhead area; however, the wind remained light and the overlying slab remains thin. In the mountains around Bozeman and Big Sky, strong winds created fresh drifts over the weekend, but wind-slabs like the one triggered on Saturday in the Northern Bridger Range have largely stabilized due to the lack of an underlying weak layer (<a href="https://www.mtavalanche.com/images/22/snowmobile-triggered-wind-slab-sm… of snowmobile triggered wind slab</strong></a>). Today, assess the snowpack for isolated areas of instability related to recent wind drifting and buried weak layers, follow safe travel protocols and be cautious on slopes where a small avalanche could sweep you into trees, rocks or off cliffs.</p>

<p>Overall, the snowpack is stable, 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>