21-22

<p>The Bridger Range and mountains around Big Sky have the most new snow and the strongest wind. Bridger Bowl’s storm total is 19” equal to 1.5” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/null/?cid=nrcseprd1314… water equivalent</u></a> (SWE) and Big Sky’s total is 12” equaling .6” SWE. Some slopes got more than this, others a bit less, but the avalanche story is the same: fresh snow and strong west wind gusting&nbsp;40-50&nbsp;mph will drift snow that can avalanche. Wind-loaded slopes near the ridgelines or in gullies are the most dangerous. This snow fell onto a weak snowpack and in areas where it is piled up deep from the wind a person can trigger avalanches large enough to kill. Our field videos in <a href="https://youtu.be/UkgkgoPLLCQ"><strong><u>Beehive Basin</u></strong></a> and in the <a href="https://www.youtube.com/watch?v=lZoIDq1ZTHk"><strong><u>Bridger Range</u></strong></a> right before the storm show this concern. Yesterday, folks in an avalanche class in Beehive dug 20+ pits and only got 2 unstable test results and they saw no slides. Today’s wind will change that. Shooting cracks in wind drifts on low-angled terrain is a sign that steeper terrain will avalanche. For today, on slopes that are wind-loaded the avalanche danger is rated CONSIDERABLE. On slopes with fresh powder that is untouched by the wind the danger is rated MODERATE. This is not “turn your brain off, look at me,” powder riding because triggering slides remains possible.</p>

<p>Storm totals in Hyalite, the southern Madison Range, Lionhead area and Cooke City were 5-7” measuring .5” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/null/?cid=nrcseprd1314…;. Wind-loading will make some slopes susceptible to triggering because all these ranges have 1 thing in common: the upper 1-2 feet of the snowpack is weak with layers of sugary facets and feathery surface hoar. These layers became unstable in Cooke City last week which is a preview of what can happen elsewhere from this recent storm (<a href="https://www.mtavalanche.com/avalanche-activity"><strong><u>Avalanche Activity list</u></strong></a>). The new snow is not enough of a load to create widespread instability, but it is enough to make avalanches possible on a few slopes that have been wind-loaded or are a bit weaker. Signs of instability like cracking of drifts or natural avalanches will be unlikely, so traveling in avalanche terrain will require homework. In some areas slopes were scoured to dirt, in others wind drifts are hard as concrete, and yet in others the weak layers are preserved. You have to dig down to know what’s under you. In Taylor Fork/Lightning Creek on Sunday I did a cursory stability test before skiing a steep slope, and was glad I did because it revealed instability I was not expecting (<a href="https://www.youtube.com/watch?v=5MFatr0c108"><strong><u>video</u></stro…;). For today, since avalanches remain possible, the danger is rated MODERATE on all slopes.</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 Bridger Range has the most snow and the most dangerous avalanche conditions. Since the storm started yesterday 14+ inches of snow has fallen measuring over an inch of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/null/?cid=nrcseprd1314… water equivalent</u></a> (SWE). This is a lot of weight to add onto a weak snowpack. West wind is drifting snow, adding even more weight. Alex talked about this danger in his video on Monday (<a href="https://www.youtube.com/watch?v=lZoIDq1ZTHk"><strong><u>video</u></stro…;). You can trigger avalanches on steep slopes today. Stay out of avalanche terrain (slopes steeper than 30 degrees) and be extra careful around anything wind-loaded. Avalanche terrain is not to be trifled with. It is still snowing, winds are blowing and the danger is getting worse. For today the avalanche danger is rated CONSIDERABLE on all slopes.</p>

<p>The avalanche danger is rising with snowfall and increasing wind. Around Big Sky about 9” of snow equal to .4” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/null/?cid=nrcseprd1314… water equivalent</u></a> (SWE) fell onto a snowpack that has weak layers in the upper 2 feet. Ian and I were in Beehive Basin yesterday and noted that conditions would deteriorate with more snow, which we now have (<a href="https://youtu.be/UkgkgoPLLCQ"><strong><u>video</u></strong></a&gt;). Increasing wind will drift the new snow into denser slabs which will avalanche. During and immediately after storms are the most dangerous for triggering slides. For today the avalanche danger is rated CONSIDERABLE on all wind-loaded slopes and MODERATE on all others.</p>

<p>The mountains around Cooke City have gotten 6” of snow since yesterday (.4” <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/null/?cid=nrcseprd1314…;) and a couple more inches are expected today. Wind has been relatively calm and our main concern in these mountains is that the new snow is falling onto a snowpack that has weak snow in the upper couple of feet. Evidence of instability include a skier and snowmobiler triggering separate avalanches this weekend (<a href="https://mtavalanche.com/node/25840"><strong><u>Wyoming Creek photo and details</u></strong></a>, <a href="https://mtavalanche.com/node/25847"><strong><u>Silver Gate photo and details</u></strong></a>). Triggering avalanches remains possible today and the avalanche danger is rated MODERATE on all slopes.</p>

<p>The mountains to the south of Big Sky to West Yellowstone have gotten 3-4” of new snow equal to .3-.4” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/null/?cid=nrcseprd1314…;. It hasn’t snowed in Carrot Basin or Lionhead since noon yesterday. Wind is picking up and will move snow and create drifts at the ridgelines which could be triggered. I was in Taylor Fork and Lightning Creek on Sunday and found mostly stable snow, but one slope was not and I decided to back off (<a href="https://www.youtube.com/watch?v=5MFatr0c108"><strong><u>video</u></stro…;). On slopes with wind-drifted snow avalanches are possible and the danger is rated MODERATE. On slopes without a wind-load 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>

<p>&nbsp;</p>

<p>The likelihood of triggering avalanches in Cooke City will largely depend on the amount and rate of snowfall today. As of 6 a.m., there is 3” of new snow equal to 0.3” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/null/?cid=nrcseprd1314… water equivalent</a> (SWE) on the ground with 1-3” expected through the day. Currently, dangerous avalanches are possible under the weight of a skier or rider. A natural avalanche on Friday near Wyoming Creek and two slides triggered by a rider and a skier north of Cooke City and Silver Gate, respectively, on Saturday were all dangerous events (<a href="https://mtavalanche.com/node/25840"><strong>Wyoming Creek photo and details</strong></a>, <a href="https://mtavalanche.com/node/25847"><strong>Silver Gate photo and details</strong></a>). Thankfully, no one was caught or injured. Avalanches today will likely be similar in size to this weekend’s activity.</p>

<p>If today’s snow pushes toward or past the expected totals, avalanches will become more likely. A thick layer of weak facets and surface hoar is buried 12-24” deep with a slab on top. This is a recipe for avalanches. Get your shovel in the snow to test the upper layers in the snowpack and weigh signs of instability such as avalanche activity, cracking or collapsing heavily in your assessment. The danger is MODERATE but be ready to dial back your plans with changing conditions.&nbsp;</p>

<p>Today’s snowfall will drive the avalanche danger in the mountains around Bozeman, Big Sky and West Yellowstone. So far, 1-2” of snow has fallen and this will do little to change generally safe avalanche conditions. However, with 3-5” expected in the northern portion of the advisory area and 1-3” in the south, conditions will change through the day. Snow is falling on a <em>weak, but not yet unstable </em>snowpack. As Alex explained in his <a href="https://www.youtube.com/watch?v=lZoIDq1ZTHk"><strong>video</strong></a&…; from the Bridger Range yesterday, if we push toward 6” of new snow or more (come on northwest flow!) avalanches will become likely.</p>

<p>As it stands this morning, large avalanches are <em>not </em>likely. As you travel, do like Doug did on Sunday and search for isolated instabilities related to buried weak layers and small wind drifts that tell you to back off steep slopes (<a href="https://www.youtube.com/watch?v=5MFatr0c108"><strong>video</strong></a&…;). When the snowpack is generally stable, travel protocols such as carrying rescue gear, watching our partners from a safe location and mitigating the added threat of terrain traps provide a buffer for safer backcountry travel.</p>

<p>Currently, the avalanche danger is LOW. However, the danger will increase through the day as snow builds up. Watch for signs of decreasing stability and adjust your plans as necessary.</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>