21-22
Woody Ridge
Skied Central Park glades on the west face of Woody Ridge today. Lots of fresh powder up high, especially at and below treeline. Open gullies like those of Central Park 1 and 2 still had visible rocks and what looked like a shallower snowpack. Dug a snow pit at 44.98558, -109.92819 just below 9400 ft in an open area on a 29º slope 276º W. Total snow depth was 110 cm at that location. There is a defined crust 67-68 cm off the ground that all the recent snow from the past few days is sitting on top of. We got an ECTP-22 on this crust/new snow interface. We also got a CT-12 SP at 18cm above the ground on an old layer of (what looked to be) rounding faceted snow grains. The snowpilot profile attached should illustrate our snow pit and test results. Skies were broken and we were in and out of a mix of cloud and blue sky - winds were calm and temperatures stayed cold all day.
small (very small) wind slabs
In the Bridger Range on December 10, 2021 2-3" of low density new snow was drifted into small soft slabs that were easy to trigger.
In the Bridger Range on December 10, 2021 2-3" of low density new snow was drifted into small soft slabs that were easy to trigger. Photo: GNFAC
Forecast link: GNFAC Avalanche Forecast for Sat Dec 11, 2021GNFAC Avalanche Forecast for Sun Dec 12, 2021
This pit was dug in Hyalite Canyon near Twin Falls. It showed 2 mm facets (sugar snow) underlying the snowpack. This layer did not break in stability tests, but anticipate these grains will get weaker with time. Photo: GNFAC
GNFAC Avalanche Forecast for Fri Dec 10, 2021
<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. </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>). 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 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&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&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. </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>. </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.