22-23
New snow and facets in Cooke
Date
Activity
Snowmobiling
Rode to Daisy Pass, back around to Henderson Bench, out to the wilderness boundary past Round Lake, and then to the bowl between Scotch Bonnet and Sheep. Low visibility, but no signs of instability or avalanches observed. Close to a foot of new snow.
Dug on Henderson Bench on a NE aspect and a N aspect at the Wilderness boundary above Astral Creek. Facets were 4F+ to 1F hardness and didn't get any break at all in the facets. Did get an ECTP11 under the new snow on Henderson Bench. Dug low on the SE face of Scotch Bonnet. Facets were more pronounced and a little softer (4F). Got an *unofficial* ECTP with extra hard taps past the prescribed 30.
New snow and wind were the primary concern. Isolated areas where you might get a slide to break deep on the facets are a less likely, but more consequential concern.
Region
Cooke City
Location (from list)
COOKE CITY
Observer Name
Ian Hoyer
Mt Ellis (main summit)
Date
Activity
Skiing
Ellis has seen alot of skier traffic since my last submission for Ellis on December 15, 2022. A quick pit was dug on a south east facing slope at 7936 feet. Height of snow = 90 cm. Bottom faceted layer was 25 cm thick. The top 65 cm of snow is beginning to consolidate into a slab. We did not experience any signs of snow instabilty. My previous submitted observation for Ellis noted surface sluffs, yesterday we had none. I believe there was a slight temperature inversion as we all remained comfortable.
Region
Northern Gallatin
Location (from list)
Mt Ellis
Observer Name
Dave Combs
Southern Bridger Whumpf
Date
Activity
Skiing
I skied on the east side of the Bridgers south of the ski area today. We dug a pit on an east aspect around 7300' and found 80 cm of snow with a similar structure to the more southerly parts of the advisory area. Well developed 2mm FC with a few DH cups sprinkled in made up the lower 40 cm or so of the snowpack (ECTP 21 on this layer) with the remainder consisting of 4F to F+ DFs. There was a razor thin "wind skin" I felt while skiing in more open areas below treeline but no major wind loading was present until at or near the ridgeline (pretty robust cornice development already for this time of year though). On our way back up just below the ridge around 7700' I felt a very large collapse that radiated out from my skis and shook some snow off of nearby branches.
Region
Bridger Range
Observer Name
Henry Coppolillo
From email: "This was in a wind-protected area with soft surface snow and no obvious prior wind loading. By this time it had gotten considerably colder, so we did not spend much time there. The total snow depth was about 115 cm, and the faceted layer went from 50 cm to the ground. ECTP23, and broke clean and smooth. There were also a couple of ECTNs in the upper snowpack above the ECTP." Photo K Birkeland
GNFAC Avalanche Forecast for Tue Dec 20, 2022
Snowpack and Avalanche Discussion
<p>Continued snowfall combined with wind-loading and persistent weak layers buried 2-4’ deep add up to heightened avalanche danger in the southern portions of the advisory area. Dangerous avalanche conditions will develop if today’s snowfall arrives early or with greater intensity than forecast.</p>
<p>Small avalanches within the new and wind-drifted snow are the most likely event. However, large, human-triggered and natural avalanches breaking 2-5’ deep have accompanied significant storms this season (<a href="https://www.mtavalanche.com/avalanche-activity"><strong><span>avalanche activity list</span></strong></a>). Periods of incremental loading (a little snow yesterday, a little snow today) are times when we can get a nasty surprise. Like the frog in slowly warming water, we must jump out before things get too hot.</p>
<p>Avoid wind-loaded slopes and carefully assess for the presence of deeply buried weak layers before considering playing on or underneath steep slopes.</p>
<p>Because large, human-triggered avalanches are possible, the danger is rated MODERATE. The danger will rise to CONSIDERABLE in wind-loaded terrain if daytime snowfall exceeds the forecasted amounts.</p>
<p><span>In the northern portions of the advisory area, human-triggered avalanches breaking on slopes with recent drifts of snow are possible. This weekend, natural and human-triggered slides generally failing 1-2 feet deep indicate this potential instability (</span><a href="https://www.mtavalanche.com/weather/wx-avalanche-log"><strong><span>Wea… and Avalanche Log</span></strong></a><span>). A skier caught and carried by a slide on Saddle Peak on Friday is a good reminder of the danger of wind-loaded slopes (</span><a href="https://www.mtavalanche.com/node/27226"><strong><span>details and photo</span></strong></a><span>). While the likelihood of triggering an avalanche has decreased since this weekend, the danger has not. </span></p>
<p><span>The lower snowpack in the mountains around Bozeman and Big Sky has weakened. We do not have a widespread problem in which we expect avalanches to fail deep in the snowpack yet, but have it on your radar. Dig down to assess and test the layer of sugary facets buried 1-3 feet deep, and let us know what you find by </span><a href="https://www.mtavalanche.com/node/add/snow_obs"><span>submitting an observation</span></a><span>. Yesterday, a pair of skiers near Divide Peak in the Northern Gallatin Range found propagation in their extended column test, an unstable result (</span><a href="https://www.mtavalanche.com/node/27263"><strong><span>observation</span…;). Watch our recent videos from </span><a href="https://www.youtube.com/watch?v=-IvzD6rum0A&feature=youtu.be"><stro… Basin</span></strong></a><span>,<strong> </strong></span><a href="https://www.youtube.com/watch?v=DbeAdSSJUqM&list=PLXu5151nmAvTi1DBS… Throne</span></strong></a><span>,<strong> </strong></span><a href="https://www.youtube.com/watch?v=En1DxtBkHt0"><strong><span>Buck Ridge</span></strong></a><span> and </span><a href="https://youtu.be/TkUux4F7dV8"><strong><span>Mount Ellis</span></strong></a><span> for more information. </span></p>
<p><span>Today, be cautious on or near recently wind-loaded slopes and test weak layers buried 1-3 feet deep for potential instability. Expect the danger to rise if tonight’s snowfall arrives earlier and with greater intensity than forecast. The avalanche danger is MODERATE.</span></p>
<p><span>If you get out, please share avalanche, snowpack or weather observations via our<a href="https://www.mtavalanche.com/node/add/snow_obs"><span> </span></a><a href="https://www.mtavalanche.com/node/add/snow_obs"><strong><span>website</s…;, email (<strong>mtavalanche@gmail.com</strong>), phone (406-587-6984), or Instagram (#gnfacobs). </span><span><span> </span></span></p>
<p><span>Snowfall combined with wind-loading and persistent weak layers buried 2-4’ deep in the snowpack add up to heightened avalanche danger in the Centennial Mountains of Island Park. The danger will increase if daytime snowfall amounts exceed forecasted amounts. Avoid wind-loaded slopes and carefully assess for the presence of deeply buried weak layers before considering playing on or under steep slopes.</span></p>
Upcoming Avalanche Education and Events
Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar.