20-21

<p>Today, moderate wind out of the west-southwest will drift the new low-density snow into thicker slabs, and a weak underlying snowpack can’t be trusted to hold much. Yesterday I was on the Bridger ridge, there was minimal wind, and I had a small 4” deep drift crack 20 feet wide under my skis (<strong><a href="https://www.mtavalanche.com/images/20/cracking-drifted-snow">photo</a><…;). Watch for blowing snow as a sign these fresh wind slabs are forming.</p>

<p>The mountains near Bozeman, Big Sky and West Yellowstone have 1-2 feet of sugary, faceted snow on the ground which will struggle to support the weight of additional snow. See our videos from the last couple weeks in the field for a good look at this weak snowpack&nbsp;(<a href="https://www.youtube.com/watch?v=FBsCjnx1G-s"><strong>Lionhead video</strong></a>, <a href="https://www.youtube.com/watch?v=3HbIdWEuo1o&amp;list=PLXu5151nmAvQDzKmH… video</strong></a>, <a href="https://www.youtube.com/watch?v=NDfD3-tTguk"><strong>Saddle Peak video</strong></a>, <a href="https://www.youtube.com/watch?v=4quJW8upKQg"><strong>Buck Ridge video</strong></a>). The snow that fell since Friday morning totaled 3-6”, and was very low density equaling 0.1-0.3” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</a> (SWE). This is not enough weight to create widespread instability, but starts a trend of decreasing stability through this week.</p>

<p>Small dry loose avalanches are possible to trigger on steeper avalanche slopes (&gt;36 degrees). A couple were reported within the new snow yesterday near Big Sky, Bridger and Cooke City. These can entrain the weak faceted snowpack below and become large enough to push a person down a slope, into trees, rocks or cliffs (<strong><a href="https://www.mtavalanche.com/images/20/full-depth-facet-sluff-s-madison"…;).</p>

<p>Today the avalanche danger is MODERATE on wind-loaded slopes, and LOW on other slopes.</p>

<p>The mountains near Cooke City have 2-4 feet of snow on the ground, and a generally stronger snowpack than the rest of the advisory area. Ian and I were there nine days ago and found some pockets of weak, sugary snow lower in the snowpack (<a href="https://www.youtube.com/watch?v=Xj-qhUPJigw"><strong>video</strong></a&…;). There have also been a few reports of buried surface hoar, so it is worthwhile to <a href="https://www.youtube.com/watch?v=Gk8W8nlUMpw&amp;list=PLXu5151nmAvQDzKmH… and perform stability tests</a> to search for these layers.</p>

<p>The snowpack near Cooke City will handle the couple inches of low-density new snow that fell yesterday, and avalanches are unlikely today. We can’t completely rule out small wind slabs that will form with moderate wind today, and dry loose avalanches in steeper avalanche terrain. If you plan to travel on steep slopes, carefully assess the snowpack and consequences of a slide. Today the avalanche 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>The snowpack around Bozeman, Big Sky, and West Yellowstone is shallow and weak. Total snow depths in the mountains generally range from 1-2 ft. Weeks of high pressure have gradually weakened this shallow snowpack (<a href="https://www.youtube.com/watch?v=FBsCjnx1G-s"><strong><u>Lionhead video</u></strong></a>, <a href="https://www.youtube.com/watch?v=3HbIdWEuo1o&amp;list=PLXu5151nmAvQDzKmH… video</u></strong></a>). Once a slab builds above this weak foundation, the snowpack will rapidly become unstable (<a href="https://www.youtube.com/watch?v=NDfD3-tTguk"><strong><u>Saddle Peak video</u></strong></a>, <a href="https://www.youtube.com/watch?v=4quJW8upKQg"><strong><u>Buck Ridge video</u></strong></a>). Last night’s few inches of low density new snow with light winds didn’t build a significant slab on most slopes. However, keep your eyes open for isolated drifts of new snow deeper than 6-8”. If you find one of these drifts, evaluate the snowpack carefully or just steer clear.</p>

<p>With such a weak foundation, expect the avalanche danger to rise as snow totals creep up in the coming days.&nbsp;</p>

<p>For today, avalanches are unlikely and the avalanche danger is LOW.</p>

<p>The snowpack around Cooke City is deeper and generally not as weak as in the rest of the advisory area. Total snow depths range from 2-4 ft. This deeper snowpack was able to handle the weeks of high pressure without weakening as much. However, we have found some pockets of weak, sugary snow lower in the snowpack and there have been a few reports of buried surface hoar, so we’re not totally in the clear going forward (<a href="https://www.youtube.com/watch?v=Xj-qhUPJigw"><strong><u>video</u></stro…;). As with the rest of the advisory area, yesterday’s new snow wasn’t enough to build much of a new slab. With a more solid foundation, the avalanche danger won’t spike as quickly as more new snow accumulates over the coming days.&nbsp;</p>

<p>The avalanche danger is LOW today.</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><u>websi…;, email (<a href="mailto:mtavalanche@gmail.com"><strong><u>mtavalanche@gmail.com</u></str…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>