A recent natural avalanche observed 1/16/23 (less than a day old) on Miller Ridge. SS-N-R1-D1.5-O and probably broke on the surface hoar layer. Photo: GNFAC
Photo from 1/16/23 of an avalanche on an east-northeast facing slope below Henderson ridge. It appeared to be snowbike triggered and 1-2+ days old. 150' wide and 250' vertical. HS-AMu-R2-D2-O. It appeared to have broke about 2' deep on that layer of surface hoar. Photo: GNFAC
Photo from 1/16/23 of a cornice triggered avalanche on Miller Ridge that broke to the ground, appears to be many days or weeks old. GNFAC.
Dug a pit on the east side of Henderson at the ridgeline above Henderson Bench. ENE, 10,075' elev. ECTP19 x3 on a layer of surface hoar buried 60cm (2 feet) deep. HS 260cm. There was an avalanche a few hundred feet north on an east-northeast facing slope below the ridge. It appeared to be snowbike triggered and 1-2+ days old. 150' wide and 250' vertical. HS-AMu-R2-D2-O. It appeared to have broke about 2' deep on that layer of surface hoar. There was also a more recent natural avalanche (less than a day old) on Miller Ridge, slightly smaller.
Skied on Henderson mountain the afternoon of 1/16. Wind was calm, snowfall was light and steady through the day with 3-4" of new snow.
Dug a pit on the east side of Henderson at the ridgeline above Henderson Bench. ENE, 10,075' elev. ECTP19 x3 on a layer of surface hoar buried 60cm (2 feet) deep. HS 260cm. There was an avalanche a few hundred feet north on an east-northeast facing slope below the ridge. It appeared to be snowbike triggered and 1-2+ days old. 150' wide and 250' vertical. HS-AMu-R2-D2-O. It appeared to have broke about 2' deep on that layer of surface hoar. There was also a more recent natural avalanche (less than a day old) on Miller Ridge, slightly smaller. SS-N-R1-D1.5-O and probably broke on the surface hoar layer.
The location of these avalanches and poor stability test scores is concerning as they are in exposed areas, implying the surface hoar will remain an issue on large, steep open slopes that will likely be heavily wind-loaded at some point.
Additional photo of a cornice triggered avalanche on Miller Ridge that broke to the ground, appears to be many days or weeks old.
Toured into Alex Lowe basin today and noticed lots of point release slides. Most started as spindrift in the cliff bands along the ridge and gained more snow as they fell into the aprons. Skied a north and south facing couloir, ski cut at the top of both runs and got the new snow to sluff most of the way down. Didn't encounter any cohesive slabs, just lots of sluff sliding down.
We skied the Throne today, near the skin track, and down low and to the north. With only a couple inches of new snow and zero wind there were no signs of instability. Our pit in the north facing chute had horrible structure, with the bottom half very facetted, but didn't offer any results. The wind hasn't blown up there for quite a while, so there's plenty of soft snow hanging around. When it does blow, it won't take long to become unstable.
<p>Dangerous avalanche conditions exist in the mountains around West Yellowstone, where 5” of new snow is adding weight to a weak layer of fragile surface hoar now buried 12-18” deep. Do not trust this layer of feathery dominos. Its spotty distribution makes snowpack assessment challenging because your snowpit may not represent nearby slopes. This layer exists on many slopes and is resulting in human-triggered slides (<a href="https://youtu.be/1mFc__nNwIk"><strong><span>Lionhead video</span></strong></a>).<span> </span>Yesterday, skiers triggered two avalanches near Hebgen Lake, one breaking 100’ wide and a foot deep (<a href="https://www.mtavalanche.com/node/27664"><strong><span>photo and details</span></strong></a><strong><u><span>, </span></u></strong><a href="http://mtavalanche.com/node/27665"><strong><span>observation</span></st…;).</p>
<p>Weak layers buried deeper in the snowpack can result in larger avalanches. Careful route-finding and conservative decision-making are essential. Avoiding slopes steeper than 30 degrees is advisable. <span> </span></p>
<p>Human-triggered avalanches are likely, and the danger is rated CONSIDERABLE.</p>
<p>Human-triggered avalanches failing within the new and wind-drifted snow, a foot deep on a layer of buried surface hoar, or on weak layers deeper in the snowpack are possible in the Madison Range, Southern Gallatin Range, and in the mountains near Cooke City. Two to 3” inches of new snow in the last 24 hours are incrementally loading the snowpack. The layer of feathery surface hoar buried a foot deep on many slopes is our primary concern (<a href="https://www.youtube.com/watch?v=hk_6xgHgTCo"><strong><span>Buck ridge</span></strong></a>, <a href="https://youtu.be/1mFc__nNwIk"><strong><span>Lionhead</span></strong></a…;, <a href="https://youtu.be/ECi646U0Rtg"><strong><span>Taylor Fork</span></strong></a>, <a href="https://youtu.be/iBS_5itbX_U"><strong><span>Cooke City</span></strong></a>). Dig, test, and build in an extra margin for error due to the spotty nature of this weak layer. It has resulted in avalanches in the Lionhead area and will eventually do the same where the snowpack structure is similar.</p>
<p>Evaluate the snowpack carefully for instability related to buried weak layers and make conservative terrain decisions with many potential avalanche problems. The danger is rated MODERATE.</p>
<p>Without significant loading from new or wind-drifted snow, triggering a large avalanche in the Bridger and Northern Gallatin Ranges is unlikely. This is not a pass to turn off our brains, a group of skiers near Frazier Basin turned around before their second steep line of the day after their snowpack assessment revealed potential instability (<a href="https://www.mtavalanche.com/node/27671"><strong><span>observation</span…;). From Mount Blackmore, Alex recommended remaining diligent about snowpack assessment and following safe travel protocols even as the likelihood of avalanches decreases (<a href="https://www.youtube.com/watch?v=UhWH5MvlW84&list=PLXu5151nmAvTi1DBS…;). Today, small avalanches breaking within the new and wind-drifted snow are concerning in terrain where they could carry you into or off terrain traps like trees, rocks and cliffs.</p>
<p>The avalanche danger is LOW.</p>
<p><span>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>Dangerous avalanche conditions exist in the Centennial Mountains in Island Park, where 5” of new snow is adding weight to a weak layer of fragile surface hoar now buried 12-18” deep. Do not trust this layer of feathery dominos. Its spotty distribution makes snowpack assessment challenging because your snowpit may not represent nearby slopes. Weak layers buried deeper in the snowpack can result in larger avalanches. Careful route-finding and conservative decision-making are essential. Avoiding slopes steeper than 30 degrees is advisable today.</span></p>
Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar.
TOMORROW, Tuesday, January 17th, 6 p.m., Silent auction and ski movies to support the Darren Johnson Memorial Avalanche Education Memorial Fund @ The Independent in Big Sky, $10
From IG:
“Snowpack observation from 1/14/23
Northern Bridgers-Frazer Basin
Chute skiers left from the exit chute/sled access boundary on ridge.
Skied a more wind protected N facing chute and experienced stability skiing. Did 2 ski cuts before entering as well as doing a shovel shear on the top ~2ft of snowpack. No clean shear for the test or other observations of instability. As a result we skied.
Decided to start skiing up another, more open face to the E and stopped to dig about 1/3 of the way up once it started to get a little steeper. Dug on a Due N slope at 8430 ft. Snow depth was 205 cm from base. Column test failed at CT11 and CT15 at 175 and 135cm from base respectively. Was a clean break. Conducted an ECT which went at ECTP12 and 14 at the same depths. We skinned off the aspect and skied conservative lines the rest of the day.”
