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GNFAC Avalanche Forecast for Fri Dec 10, 2021

Snowpack and Avalanche Discussion

<p>Near Cooke City almost a foot of new snow (0.9” <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/null/?cid=nrcseprd1314… Water Equivalent</u></a>) fell since Wednesday afternoon, accompanied by strong winds. This snow comes on top of the 8” that fell earlier in the week. Avalanches breaking in this week’s new snow are the primary concern today, particularly where the new snow has been blown into deeper drifts.&nbsp;</p>

<p>On some slopes the new snow fell onto bare ground, while on others it is adding to a 2-3 ft deep layered snowpack that has been accumulating since October. Slopes that held snow before this week have weak layers in the lower snowpack (<a href="https://www.youtube.com/watch?v=1Nt5LOMI1PQ"><strong><u>video</u></stro…;, <a href="https://youtu.be/O29XGDZBL8c"><strong><u>video</u></strong></a&gt;). These weak layers aren’t super concerning, but they have just gotten loaded for the first time. It’s worth digging to look for and evaluate these layers before committing to steep slopes. Human triggered avalanches are possible and the avalanche danger is MODERATE.</p>

<p>Less new snow fell near Bozeman, Big Sky, and West Yellowstone. On slopes where this new snow has <strong><em>not</em></strong><strong> </strong>been drifted into deeper drifts, avalanches are unlikely. On Wednesday, Doug and Dave found weak&nbsp;layers developing mid-pack in the Bridgers, but without a load we are not very concerned about them right now (<a href="https://www.youtube.com/watch?v=8yJ1-BzM8Eg&amp;list=PLXu5151nmAvT1nrM2…;

<p>The slopes to be mindful of are those where the new snow has piled up into thicker cohesive drifts. Yesterday, Doug was in Hyalite checking out the snowpack in Avalanche Gulch and near Silken Falls (<a href="https://www.youtube.com/watch?v=065JmnekjVs&amp;list=PLXu5151nmAvT1nrM2…;). Overall he was encouraged by the lack of instability he found in the wind drifted gullies, but he still encouraged a healthy skepticism of drifts. What he’s worried about is that you might still be able to trigger a wind slab like the one ice climbers triggered last weekend in a gully in Hyalite (<a href="https://www.mtavalanche.com/node/25065"><strong><u>photos and report</u></strong></a>). Be ready to back off a slope if you feel the snowpack stiffening under your feet or see cracks shooting out in front of you.&nbsp;</p>

<p>While we are generally optimistic about stability based on what we’ve found so far, it is still early season and we still have very limited data. Uncertainty remains high. Deal with this uncertainty by treating your early season trips into the mountains as information gathering missions. Be cautious, be on the search for instability and if you find it, back off and then <a href="https://www.mtavalanche.com/node/add/snow_observation"><u>let us know</u></a>.&nbsp;</p>

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

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Upcoming Education Opportunities:

Get your avalanche brain ready for the season at one of the many classes listed on our education calendar, and list of upcoming events below. Don’t delay preparing and inspecting your avalanche gear. Get some tips from Dave Zinn in this Pre-Season gear check video.

For the Bozeman Ice Fest we investigated the Silken Falls and Avalanche Gulch gulleys. They were wind-loaded and had weak snow mid-pack that was unreactive. Avalanches in these gulleys would be deadly, so be extra vigilant in your assessment before crossing. Photo: GNFAC

Northern Gallatin, 2021-12-09

For the Bozeman Ice Fest we investigated the Silken Falls and Avalanche Gulch gulleys. They were wind-loaded and had weak snow mid-pack that was unreactive. Avalanches in these gulleys would be deadly, so be extra vigilant in your assessment before crossing. Photo: GNFAC

Northern Gallatin, 2021-12-09