21-22

<p>It just keeps snowing and blowing in the mountains near Cooke City and West Yellowstone. It has snowed 4-5 ft over the last week and a half accompanied by strong, generally westerly, winds piling that snow into deeper drifts. This has put a lot of weight on the snowpack and keeps the avalanche danger elevated. You are <em>likely</em> to trigger a large, dangerous avalanche if you travel on any steep wind-loaded slope. Avalanches could break on interfaces within the recent snow or on weak layers near the ground. Monday’s avalanche accident that killed two snowmobilers on a wind-loaded slope near Cooke City reminds us of the seriousness of our travel decisions (<a href="https://www.mtavalanche.com/accident/21/12/30"><strong><u>accident report</u></strong></a>). Dave and I were near Lionhead yesterday and the continued loading meant that even without signs of instability we still weren’t trusting the weak layers low in the snowpack (<a href="https://www.youtube.com/watch?v=K4yEaUsqo6A"><strong><u>video</u></stro…;). Avoid steep slopes that have been wind-loaded and carefully evaluate the snowpack before riding any steep slope. The danger is rated CONSIDERABLE on wind-loaded slopes and MODERATE on all others.</p>

<p>In the Bridger Range there is a layer of weak snow buried in the middle of the thin snowpack (<a href="https://youtu.be/kXE-CWnV_NY"><strong><u>video</u></strong></a&gt;). This layer is reacting in stability tests and it is possible to trigger avalanches on it. Triggering avalanches in fresh wind drifts is also a possibility. Pay particular attention where these concerns overlap. Dig to search for the weak layer. Look for and pay attention under your feet or sled for the smooth, denser pillows of snow that indicate wind drifted snow. Human triggered avalanches are possible and the avalanche danger is MODERATE.</p>

<p>Strong winds and a bit of new snow have formed wind drifts that could be triggered by a skier or rider today. Look for these drifts near ridgelines, behind tree islands, and in gullies. Pay extra attention in high consequence terrain where even getting swept off your feet would put you into a bad situation. Until it gets substantially loaded, the lower snowpack is mostly stable. Human triggered avalanches are possible on wind-loaded slopes which have a MODERATE danger. On all other slopes the danger is rated LOW.&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>It snowed more than 4 feet (4.3” <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/null/?cid=nrcseprd1314… water equivalent</u></a>) in the last 8 days in the southern mountains including Cooke City (<a href="https://www.mtavalanche.com/weather/wx-avalanche-log"><strong><u>weather log</u></strong></a>). Yesterday’s 4” of new snow coupled with strong wind and more snow today is making dangerous avalanche conditions on wind-loaded slopes. On Monday two snowmobilers were killed on one of these slopes and these are not any safer today (<a href="https://www.mtavalanche.com/node/25278"><strong><u>incident</u></strong…;). Other avalanches in Cooke City (<a href="http://www.mtavalanche.com/images/21/natural-slide-henderson-wind-loade…;, <a href="http://www.mtavalanche.com/images/21/human-triggered-avalanche-mount-ab…;) and “one monster whumph” in Bacon Rind are signs that instability continues. A whumpf is the sound of a weak layer breaking and propagating under you. It is an avalanche on flat terrain and a sign of instability. Avoid avalanche terrain that has been wind-loaded. Slopes without a wind load still harbor a weak layer of faceted, sugary snow that is propagating in stability tests. Dig and investigate slopes before blindly committing to avalanche terrain. For today, the danger is rated CONSIDERABLE on wind-loaded slopes and MODERATE on all others.</p>

<p>Dave gets a gold star for “walking the talk”. We preach hunting for instability even when things seem safe. Yesterday, Dave and his partner toured into the northern Bridger Range with an expectation of finding stable snow. It did not turn out that way. He dug his first pit low on a slope and surprisingly found a weak layer breaking clean. He dug 5 more pits and got breaks on some more. A thin layer of weak, faceted crystals (called near-surface facets) was in the middle of the 2-3 foot deep snowpack. He did not get into avalanche terrain. Instead, he made a <a href="https://youtu.be/kXE-CWnV_NY"><strong><u>video</u></strong></a&gt; explaining why. Other skiers found this layer too. Given the discovery of this new weak layer and potential for triggering avalanches on it we recommend digging and avoiding avalanche terrain if you find it. Additionally, strong west wind is building shallow drifts that could be triggered. For today the avalanche danger is rated MODERATE on all slopes.</p>

<p>Strong west wind is blowing in the northern Madison and northern Gallatin Ranges. Two inches of new snow and a few more today will be blown into drifts. These will be found near the ridgelines and in gullies and I anticipate a person could trigger a few wind slabs. On slopes without a wind load the stability is good. Although there is weak, faceted snow near the ground it is currently not a problem. In the last week we’ve either visited or had reports from Mt Ellis, Mt Wheeler, Lick Creek, Mt Blackmore, Beehive Basin (<a href="https://youtu.be/ePMCJs3qAs0"><strong><u>video</u></strong></a&gt;) and Buck Ridge (<a href="https://youtu.be/cf-qqv2Ssjw"><strong><u>video</u></strong></a&gt;) where generally stable conditions exist.</p>

<p>For today, it remains possible to trigger slides on wind-loaded slopes which have a MODERATE danger. On all other slopes avalanches are unlikely and the danger is rated LOW.&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>