GNFAC Avalanche Forecast for Tue Jan 11, 2022
<p>Heavy snowfall in the southern portions of our advisory area ended on Saturday with storm totals peaking in the mountains around Cooke City (<a href="https://mtavalanche.com/weather/wx-avalanche-log"><strong>weather log</strong></a>). Strong winds transported snow and added additional load to slopes already on the edge. Correspondingly, riders and skiers submitted observations of natural and human-triggered avalanches (<a href="https://www.mtavalanche.com/images/22/natural-near-lulu-pass-north-scot…;, <a href="https://www.mtavalanche.com/images/22/natural-avalanche-republic-crk"><…;, <a href="http://www.mtavalanche.com/node/25458"><strong>details</strong></a>, <a href="https://www.mtavalanche.com/node/25432"><strong>details</strong></a>). Today, avalanches breaking 1-3’ deep within recent drifts or storm snow remain possible, slides failing deeper on buried weak layers near the bottom of the snowpack are less likely but are not out of the question. While less snow fell in the Southern Madison and Southern Gallatin Ranges and the Lionhead area, the same setup exists as in Cooke City. Weaker snow in the middle and bottom of the snowpack heightens the danger until it fully adjusts to recent loading.</p>
<p>Carefully assess the snowpack for unstable weak layers, remain skeptical of recently wind-loaded slopes around ridgelines and cornices and follow safe travel protocols to limit your group’s exposure. Human-triggered avalanches are possible, and the danger is MODERATE.</p>
<p>Three days have passed since the last snowfall in the northern ranges of the advisory area and the wind no longer has access to soft snow for transport. Two days ago, a group of skiers in Beehive Basin triggered a significant cornice collapse that caused a small avalanche below but failed to propagate out to the wider slope (<a href="http://www.mtavalanche.com/node/25463"><strong>photos and details</strong></a>). Also in Beehive Basin this weekend, Doug and other groups reported thin wind drifts that cracked under their skis but generally found a stabilizing snowpack in which weak layers were not propagating failure (<a href="https://www.youtube.com/watch?v=4bHDClbuKT8&list=PLXu5151nmAvT1nrM2…;). Skiers near Divide Peak reported similar conditions. Yesterday, the Big Sky Ski Patrol triggered an avalanche during avalanche mitigation that broke on weak layers near the ground, slides like this in the backcountry are unlikely today but this is a good reminder of why we assess slopes for areas of isolated instability. </p>
<p>Follow accepted safe travel practices with one person exposed to hazard at a time and manage your use of terrain to minimize the potential harm from small slides. The avalanche danger is rated LOW.</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>
Upcoming Education Opportunities
The West Yellowstone Beacon Park is up and running! Stop by to check it out and practice with your rescue gear.
See our education calendar for an up-to-date list of all local classes. Here are a few select upcoming events and opportunities to check out:
Rockslide
Rode sleds up trail and then skied to a high point of 9400ft. Generally supportable snowpack for skiing. Not as much for sledding. Lots of snow for this time of year. Good coverage. About 2 feet of new snow in past week (2 inches SWE). Dug to the ground at 9200ft northeast aspect. Height of snow 140 cm. Only real problem layer that was reactive in an extended column test was facets on the ground, their distribution was more spotty the higher we got in elevation, and the more deeply buried they are. No collapsing or cracking or other obvious signs of instability. But if someone were to trigger an avalanche on this layer of facets on the ground it would be catastrophic because it would release the entire winter's snowpack - about a 4 foot deep slab.
Divide Peak
We dug a pit on the east ridge of Divide Peak on a southern aspect at approximately 9760ft. There was a calm breeze from the northwest and the day was mostly sunny. We recorded an HS of 115cm. We observed that the top layer of recent snow/ wind drift (~8cm) slide readily when isolated, but little sluff actually occurred after our group, and many other groups, skied the slope. We recorded an ECTN 8 @ 8cm, and an ECTN 30 @ 74cm. At around 3pm we began to notice the effect of the sun and observed an occasional roller ball on due south aspects.
Avalanche Activity in Centennials, Mt Jefferson
We rode from the Sawtell Road up to Mount Jefferson then through to upper Hell Roaring Creek on a tour of the range and accident sites with three members of the Fremont County SAR team, Randy, Nick and Justin. The ride was a beautiful traverse of the range. There was one very large natural avalanche that failed a week earlier on Mount Jefferson and several others that broke during the last loading event. We dug a couple of snowpits, finding a DEEP (200-230 cm HS) and mostly stable snowpack (ECTXs). Brett Rasmusen found a layer of NSF in the head of the White Elephant drainage and an avalanche nearby at Lionhead is indicative of a more widespread weak layer 1-2’ under the surface. LOW / MODERATE seemed appropriate on deeper instabilities, but with anticipated loading, we must communicate the concern about this new weak layer and the potential for large avalanches breaking in the upper part of the snowpack.
GNFAC Avalanche Forecast for Mon Jan 10, 2022
<p>It has been almost two days since heavy snowfall ended, and strong southwest winds have decreased to moderate. Over the last two days skiers and riders near Cooke City saw a handful of avalanches that broke on wind-loaded slopes during the storm on Thursday through Saturday (<a href="https://www.mtavalanche.com/images/22/natural-near-lulu-pass-north-scot…;, <a href="https://www.mtavalanche.com/images/22/natural-avalanche-republic-crk"><…;, <strong><a href="http://www.mtavalanche.com/node/25458">details</a></strong>, <a href="https://www.mtavalanche.com/node/25432"><strong>details</strong></a>). All these slides failed 1-3 feet deep within the recent snow that fell. Today it is possible for a skier or rider to trigger avalanches similar to these, especially on recently wind-loaded slopes. Avalanches could break deeper and wider on weak layers near the bottom of the snowpack. These larger slides are becoming less likely, but we’re not free of worry until we are further from the recent storm without seeing any of these deeper slides. Before riding steep slopes carefully assess the snowpack for signs of wind-loading and potential buried weak layers. Today avalanches are possible to trigger, and avalanche danger is MODERATE.</p>
<p>Yesterday in Beehive Basin a skier triggered a cornice from a ridgeline that created an avalanche on a heavily wind-loaded slope. Nobody was caught or harmed (<strong><a href="http://www.mtavalanche.com/node/25463">photos and details</a></strong>). Doug and his partner were skiing in Beehive Basin and saw recent strong wind had transported all the snow it could (<strong><a href="http://www.mtavalanche.com/images/22/sastrugi-wind-sculpted-snow">photo…;), and they found a layer of small facets that was buried by recent snow and wind drifts (<strong><a href="https://www.youtube.com/watch?v=4bHDClbuKT8&list=PLXu5151nmAvT1nrM2…;). Today it is possible to trigger recently formed drifts of snow, especially if they formed on top of this recently buried weak layer. Avalanches could also break deeper in the snowpack on weak layers near the ground, particularly near West Yellowstone and in the southern Madison and southern Gallatin ranges where there has been more snow and more avalanches occurred earlier this season on these deeper layers.</p>
<p>Before riding steep slopes assess potential for unstable drifts and be certain there are no potentially unstable buried weak layers. Human triggered avalanches are possible, and the avalanche danger is MODERATE.</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>
Upcoming Education Opportunities
The West Yellowstone Beacon Park is up and running! Stop by to check it out and practice with your rescue gear.
See our education calendar for an up-to-date list of all local classes. Here are a few select upcoming events and opportunities to check out:
Shooting cracks en route to ridge of Beehive Basin
Natural new snow avalanche on Emigrant Peak
From obs 1/10/21: "Saw this recent natural slide, probably a day or two old, while skiing on Emigrant. Start zone approx 10,400ft, E facing. We guessed the crown was 3-5ft deep. Evidence of wind loading on similar surrounding slopes, suggesting wind slab as culprit." Photo: T. Benson
From obs 1/10/22: "Saw this recent natural slide, probably a day or two old, while skiing on Emigrant. Start zone approx 10,400ft, E facing. We guessed the crown was 3-5ft deep. Evidence of wind loading on similar surrounding slopes, suggesting wind slab as culprit." Photo: T. Benson
Skier triggered cornice beehive basin
From email 1/9/21: "Skier triggered cornice failure avalanche. Broke at skis 10-12 feet from the lip. No one caught or injured."