20-21

<p>It is snowing hard at Bridger Bowl as I write this at 6:30 a.m. Already 5” has fallen with a <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent </u></a>of .6”. The snow will stop this morning, but the winds will not. The Bridger Range has very weak snow which will avalanche naturally today. Stay clear of avalanche terrain. Expect to get whumpfs and cracks on the flats which could trigger avalanches on connected slopes. This is not a nuanced danger. For today the avalanche danger is rated HIGH on all wind-loaded slopes and CONSIDERABLE on all others. Triggering avalanches is likely and I urge folks to be conservative in their travels.</p>

<p>The snowpack south of Bozeman to Big Sky and West Yellowstone is weak. We have seen time and time again how just a little snow is enough to create unstable conditions. Two to 4” of snow is not much weight in a normal season on an average snowpack, and this year is neither. The foundation of our snowpack consists of weak, sugary snow that crumbles away. Winds are blowing this snow into drifts that will crack and likely avalanche. Expect to find these areas near ridgetops.</p>

<p>Collapses, or audible whumpfs, are an avalanche on flat terrain. It is when your weight fractured a weak layer that propagated some distance. Besides avalanches themselves, whumpfs are the next best sign that slopes are unstable. After a fresh load of snow I expect the snowpack will be “talking” to us, and we should listen to her warning.&nbsp;</p>

<p>Today, weak snow at the ground will be under stress on wind-loaded slopes, just as Ian and I saw on Buck Ridge (<a href="https://www.mtavalanche.com/node/23454"><strong><u>details</u></strong>…;) and Dave and I found at Lionhead (<a href="https://youtu.be/rWeNgK6_PTs"><strong><u>video</u></strong></a&gt;, <a href="https://www.mtavalanche.com/images/20/above-ski-hill-profile-27-dec"><s…;). For today, the avalanche danger is rated CONSIDERABLE on wind-loaded slopes since avalanches are likely and the instability is widespread. All other slopes have a MODERATE danger.</p>

<p>Cooke City has a 5 foot deep snowpack that does not have widespread weak layers, however, not every single slope is stable. Yesterday morning a snowmobiler triggered an avalanche on Crown Butte that broke 1-2 feet deep and 150 feet wide. No one was caught. Dave and Ian took <a href="https://www.mtavalanche.com/photos"><strong><u>pictures</u></strong></a…; and made a <a href="https://youtu.be/UEY5A4YXibg"><strong><u>video</u></strong></a&gt; at the crown (more <a href="https://www.mtavalanche.com/node/23465"><strong><u>details</u></strong>…;). This avalanche was in the midst of a sea of snowmobile tracks on big slopes; an isolated, yet serious event. Fortunately, this slide is in full view on the way to Daisy Pass and both riders and skiers can recalibrate their plans since the potential of triggering avalanches is not obvious when we are surrounded by wall-to-wall tracks. These are times when we need to adhere to our basic safety protocols of traveling with a partner, only exposing one person at a time on slope and carrying rescue gear. In other words, always be prepared for the worst, especially when avalanches are unlikely. For today the avalanche danger is rated LOW on all slopes.</p>

<p>The snowpack in all our ranges except Cooke City is weak. Snow that fell in October rotted into sugary facets from exposure to clear skies and little snowfall. These grains do not bond well and they fall out of a fist like sand. These grains are weak and cannot support much weight. This layer is 1-2 feet thick and blankets the mountains from West Yellowstone to the Bridger Range, as well as most of the western US. Small snowstorms are slowly building a slab of meatier snow which the facets are struggling to support. Whumpfs, cracks, small avalanches, and unstable test scores are warnings from Mother Nature that the snowpack structure is poor. These signs have been reported <a href="https://www.mtavalanche.com/weather/wx-avalanche-log"><strong><u>13 of the last 14 days</u></strong></a>. Yesterday, Ian and I rode into Buck Ridge and saw recent avalanches, had collapsing and cracking of the snowpack when we post-holed over to dig a snowpit, and got unstable test results. <a href="https://www.mtavalanche.com/photos"><strong><u>3 pictures</u></strong></a>, one <a href="https://www.mtavalanche.com/images/20/3rd-yellowmule"><strong><u>snowpi…; </u></a>and a <a href="https://youtu.be/7jzopnikTNE"><strong><u>video</u></strong></a&gt; document the problem through all these ranges.&nbsp;</p>

<p>It is not an issue of <u>if</u> avalanches will occur, but an issue of <u>when</u>. We need more snow to tip the scales towards widespread instability. Without the weight of new or wind blown snow being added to slopes the chances of triggering avalanches is decreasing, yet still possible. It is difficult to determine which slope will slide and which will not because the snow structure is uniformly bad everywhere. The only defense against this threat is to treat every slope with suspicion. It’s like driving on icy roads with bald tires; you can do it, but it might not end well.&nbsp;</p>

<p>For today the avalanche danger is rated MODERATE on all slopes since our snow structure is poor and triggering slides is possible.</p>

<p>Cooke City has a deep snowpack and only a few isolated instabilities. Without snowfall actively loading slopes, today’s concerns are limited to areas where the snowpack is thin and harboring weaker snow (i.e. in valley bottoms or near steep, craggy areas). Collapses (whumpfs) and cracks are a sign you found it. These mountains do not have widespread weak layers which makes it even more important to hunt for instability by digging and testing the snowpack before committing to avalanche terrain. Alex is in the area and reported that stability has improved from our visit last week. In the absence of new snow and widespread/persistent weak layers, the avalanche danger is rated LOW since natural and human triggered slides are unlikely.&nbsp;&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><u>websi…;, email (<a href="mailto:mtavalanche@gmail.com"><strong><u>mtavalanche@gmail.com</u></str…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>