21-22

<p>Over 3 feet of snow fell outside Island Park, Idaho since Sunday and we are continuing the AVALANCHE WARNING for this area since very dangerous avalanche conditions exist. The avalanche danger is rated HIGH on all slopes. Avalanches can be triggered from low on the slope and from adjacent slopes far away. Do not get on or underneath steep slopes.</p>

<p>In the last 24-hours a foot of snow amounting to 1” of <a href="https://missoulaavalanche.org/2021/01/what-is-swe-snow-water-equivalent… water equivalent</u></a> (SWE)&nbsp; fell in the mountains south of Big Sky to West Yellowstone. Since Saturday this amounts to over 30” of snow. Yesterday, Ian and his partner rode into Taylor Fork and saw wind drifts shoot deep cracks far ahead on the trail. Dave was in Lionhead on Monday and triggered a “whumph” on his skis (<a href="https://www.youtube.com/watch?v=Vo9-92FngRA&amp;list=PLXu5151nmAvT1nrM2…;). These two obvious signs of instability will continue today. They are warnings to not get into avalanche terrain. A few natural avalanches will be seen in the backcountry which is a red flag to stay off slopes since triggering avalanches is likely, no matter if you are on skis or a snowmobile. The snowpack depth doubled in some spots and even deeper wind-drifts are on many aspects and elevations.&nbsp;</p>

<p>Today is a day to be careful around avalanche terrain. The fresh snow is inviting, but it needs time to stabilize and strengthen. For today the avalanche danger is rated CONSIDERABLE on all slopes.&nbsp;</p>

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<p>This morning folks around Bozeman and Big Sky are scrambling to find their snow shovels. It snowed as much in town as it did in the mountains, about 8” (.5-.7 SWE). West to northwest wind is gusty and blowing snow. The snowpack is 2-3 feet deep and weak layers of sugary, faceted snow are found in most of our snowpits (<a href="https://www.mtavalanche.com/images/21/thin-snowpack-hyalite"><strong><u… of weak snow in Hyalite</u></strong></a>, <a href="https://www.youtube.com/watch?v=8yJ1-BzM8Eg&amp;list=PLXu5151nmAvT1nrM2… video</u></strong></a>). With last night’s snow and wind-loading these layers could be triggered. Wind drifts at the ridgelines and in gullies should be avoided today.&nbsp; Wind drifts will crack and avalanche from human triggers so keep your powder stoke in check. As evidence, yesterday a skier triggered a shallow and small wind slab north of Bridger Bowl on <a href="https://www.mtavalanche.com/node/25142"><strong><u>the Ramp</u></strong></a>. For today the avalanche danger is rated CONSIDERABLE on all wind-loaded terrain since triggering wind-drifts will be easy. Slopes without a wind-load have a MODERATE danger.</p>

<p>The mountains around Cooke City got 2” since yesterday morning bringing their storm total since Saturday to 17-20” (1.7” <a href="https://missoulaavalanche.org/2021/01/what-is-swe-snow-water-equivalent…;). Wind was blowing most of that time loading and drifting slopes. There is a weak layer buried in the snowpack that Ian and Alex found last week (<a href="https://www.youtube.com/watch?v=1Nt5LOMI1PQ"><strong><u>Cooke City video 1</u></strong></a>, <a href="https://youtu.be/O29XGDZBL8c"><strong><u>Cooke City video 2</u></strong></a>).&nbsp; It was windy the last 4 days (<a href="https://www.mtavalanche.com/weather/stations/cooke-city"><strong><u>Lulu Pass Weather Station</u></strong></a>) and on slopes with wind-drifts this layer is our primary concern. It’s always a good practice to avoid wind-loaded slopes. Dig and assess the snowpack before committing to avalanche terrain and don’t let your guard down. For today the avalanche danger is rated MODERATE on wind-loaded slopes and LOW on all others.&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>

<p>The Gallatin National Forest Avalanche Center is issuing an avalanche warning for the Centennial Mountains outside Island Park, Idaho. The avalanche danger is HIGH on all slopes. Natural and human-triggered slides are very likely.&nbsp;A large amount of new snow with strong wind are creating unstable conditions over a wide area.&nbsp;Very dangerous avalanche conditions. Backcountry travelers should stay off of steep slopes and stay away from the bottom of steep slopes. Avalanches can be triggered from flat terrain. Steep slopes can avalanche far above and run into lower angled terrain. <a href="http://www.mtavalanche.com/forecast/centennials"><u>www.mtavalanche.com…; for more detailed information.</p>

<p>This week’s storm has a bull’s eye painted on the West Yellowstone area with Lionhead, and the Southern Madison and Southern Gallatin Ranges feeling the effects with 21” equal to 1.8-2” of snow water equivalent (SWE) since Saturday. Strong winds and another blast of snow today are creating dangerous avalanche conditions on all slopes. When we rode Lionhead on Monday, we found heavily wind-drifted slopes already struggling with the weight of the new snow. One large drift expressed this instability with a loud collapse or “whumph” (<a href="https://www.youtube.com/watch?v=Vo9-92FngRA&amp;list=PLXu5151nmAvT1nrM2…;). At the same time, skiers in the Taylor Fork triggered wind drifts on a test slope that broke as a small, but thick slab avalanche (<a href="https://www.mtavalanche.com/images/21/thick-wind-slabs-taylor-fork"><st…;). Continued snowfall throughout the day will increase the danger.&nbsp;</p>

<p>Careful snowpack evaluation, cautious route-finding and conservative decision-making are essential. The danger is rated CONSIDERABLE on all slopes.</p>

<p>Cooke City has received 15” of snow since Saturday equal to 1.5” of SWE with strong winds stripping some slopes and loading others. Last week, Alex and Ian found weak layers buried deeply in the snowpack (<a href="https://www.youtube.com/watch?v=1Nt5LOMI1PQ"><strong><u>Cooke City video 1</u></strong></a>, <a href="https://youtu.be/O29XGDZBL8c"><strong><u>Cooke City video 2</u></strong></a>). These weak layers have not produced avalanches or propagated in unstable test scores yet, and our primary concern revolves around steep slopes with the added weight of wind-loaded snow. Avoid wind-loaded slopes and dig down to assess whether deeper weak layers are nearing their breaking point as continued snowfall adds weight and stress to the snowpack.&nbsp;</p>

<p>Heightened avalanche conditions exist on wind-loaded slopes. On non-wind-loaded slopes, slab avalanches are unlikely. Watch for signs of decreasing stability as today’s snow adds up. The danger is rated MODERATE on wind-loaded slopes and LOW on all others.</p>

<p>With the exception of slopes loaded by the recent wind (<a href="https://www.youtube.com/watch?v=lyl9dBUt0u4&amp;list=PLXu5151nmAvT1nrM2… video</u></strong></a>), the snowpack in the mountains around Bozeman and Big Sky is generally stable. Yesterday in the Bridger Range, we found some slopes stripped down to the dirt and small areas with drum-like wind-slabs. This weekend, climbers in the gullies of Hyalite observed shooting cracks in localized drifts and had them collapse under their feet (<a href="https://www.mtavalanche.com/images/21/propagating-cracks-along-top-and-…;, <a href="https://www.mtavalanche.com/images/21/cracking-drifts-hyalite"><strong>…;, <a href="https://www.youtube.com/watch?v=065JmnekjVs&amp;list=PLXu5151nmAvT1nrM2… Hyalite gullies video</u></strong></a>). We are finding weak facets on some slopes, but they will not be a concern until they are loaded with significant new snow (<a href="https://www.mtavalanche.com/images/21/thin-snowpack-hyalite"><strong><u… of weak snow in Hyalite</u></strong></a>, <a href="https://www.youtube.com/watch?v=8yJ1-BzM8Eg&amp;list=PLXu5151nmAvT1nrM2… video</u></strong></a>). The 5-7” in the forecast today is unlikely to tip the scales but watch for signs of decreasing stability as today’s snow adds up.&nbsp;</p>

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