GNFAC Avalanche Forecast for Tue Mar 23, 2021
<p>Since Friday, the mountains received 15-23” of new snow equal to 1.4-1.8” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</a> (SWE). Winds have been strong enough to transport snow at higher elevations and near ridgelines but overall have remained light to moderate through the storm. Avalanches today are all about the interface between the old and new snow. The snow fell onto an ice crust or a wet snow surface on many slopes and is bonding well. However, on some slopes that stayed cool during the March warm-up, new snow fell onto a thin, weak layer of near-surface facets. On Sunday, separate groups of skiers unintentionally triggered two avalanches in Hyalite Canyon. One was a close call that carried a skier several hundred feet down the mountain (<a href="https://mtavalanche.com/node/24673"><strong>Alex Lowe Peak details and photos</strong></a>, <a href="https://mtavalanche.com/node/24676"><strong>Mount Blackmore details</strong></a>). In Beehive Basin, a group triggered several loose snow avalanches or sluffs that would be hazardous in technical terrain (<a href="https://mtavalanche.com/node/24678"><strong>details and photo</strong></a>). On Saturday, skiers triggered a thin avalanche near Hyalite Peak that broke 150’ away from them and 150’ wide (<a href="https://www.mtavalanche.com/node/24668"><strong>photo and info</strong></a>).</p>
<p>Stack the deck in your favor by following safe travel protocols and assessing this interface with quick snowpits, each taking less than 2-minutes, as I demonstrate in my 59-second <a href="https://www.youtube.com/watch?v=sqn0KFZqXYs"><strong>video</strong></a&…;. Expect changes at different elevations and aspects, so dig more shallow pits rather than one deep one. Watch our recent field videos from <a href="https://youtu.be/zCKlHstJTqc"><strong>McAtee Basin</strong></a>, the <a href="https://www.youtube.com/watch?v=TAWRM8yRgUM&list=PLXu5151nmAvQDzKmH… </strong></a>and <a href="https://www.youtube.com/watch?v=U1b5LjWLTac&list=PLXu5151nmAvQDzKmH…; Ranges, and <a href="https://www.youtube.com/watch?v=VQd7lPN6zTQ&list=PLXu5151nmAvQDzKmH… City</strong></a> for examples of where we found this layer.</p>
<p>Avalanches failing deeper than the interface are unlikely; however, the snow is stacking up. If you trigger a slide at the interface, now pushing 2’ deep, it is possible for it to step-down into older weak layers.</p>
<p>Today, human-triggered avalanches are possible, and the danger is rated 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 Avalanche Education and Events
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:
March 24, 6 p.m., Free 1-Hour Avalanche Awareness, online Link to Join HERE
GNFAC Avalanche Forecast for Mon Mar 22, 2021
<p>Since Friday, the mountains received 10-17” of heavy snow, equal to 0.9-1.6” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</a> (SWE). Winds increased to 10-20 mph from the west to southwest, transporting soft snow into unstable drifts. Our primary avalanche concerns today exist within this new and wind drifted snow. Yesterday, a group of skiers triggered an avalanche that broke 10” deep about 150’ above them, catching one person and carrying them 250 vertical feet down Alex Lowe Peak (<a href="https://mtavalanche.com/node/24673"><strong>details and photos</strong></a>). As they returned to the trailhead, they saw another group trigger an avalanche on the east face of Mount Blackmore (<a href="https://mtavalanche.com/node/24676"><strong>details</strong></a>). Thankfully, no one was injured in either event, but it was a close call. On Saturday, a group near Hyalite Peak triggered a 4” deep, 150’ wide avalanche from 150’ away (<a href="https://www.mtavalanche.com/node/24668"><strong>photo and info</strong></a>). While small relative to February’s deep slab avalanches, none of these slides should be underestimated especially in steep or extreme terrain.</p>
<p>Assess the stability of the interface between old and new snow by digging down 2’ and performing quick extended column tests remembering that it will change at different aspects and elevations. Yesterday at Buck Ridge, we found a weak layer of near-surface facets that consistently failed in our stability tests after digging four other pits along the way with stable results (<a href="https://youtu.be/zCKlHstJTqc"><strong>video</strong></a>). The new snow is generally bonding well, but in areas with a wet snow interface (<a href="https://www.youtube.com/watch?v=smo7R2A_6ZU&list=PLXu5151nmAvQDzKmH…’s Bacon Rind video</strong></a>) or a weak, faceted interface, it is not. Watch Alex’s <a href="https://www.youtube.com/watch?v=TAWRM8yRgUM&list=PLXu5151nmAvQDzKmH…; from the Bridger Range and Doug’s videos from the <a href="https://www.youtube.com/watch?v=U1b5LjWLTac&list=PLXu5151nmAvQDzKmH… Range</strong></a> and <a href="https://www.youtube.com/watch?v=VQd7lPN6zTQ&list=PLXu5151nmAvQDzKmH… City</strong></a> to see how it is playing out regionally.</p>
<p>Today, recent and ongoing snowfall with increasing wind make human-triggered slides possible. The danger is rated 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 Avalanche Education and Events
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:
March 24, 6 p.m., Free 1-Hour Avalanche Awareness, online Link to Join HERE
Small Skier Triggered Sluff, Beehive Basin
From email: "We both set off some small sluffing on the west side of the ridge between Middle and Beehive on our way out; the snow on that a aspect was a lot thinner and more prone to sliding on the older icy crust under the new snow. Photos are from below where we skied out; we dropped onto the west-facing slopes maybe 100' south of the prayer flags."
From email: "We both set off some small sluffing on the west side of the ridge between Middle and Beehive on our way out; the snow on that aspect was a lot thinner and more prone to sliding on the older icy crust under the new snow. Photos are from below where we skied out; we dropped onto the west-facing slopes maybe 100' south of the prayer flags." Photo: P Calabro
Skier Triggered Avalanche, Mount Blackmore
From email: "On our way out (from Alex Lowe Peak) we watched two skiers climbing to the top of a gully on the SE face of Blackmore... When I looked up again 5 minutes later, the gully had slid. Luckily, based on their tracks it looks like they triggered it from the top without getting caught and then skied it. The first skier was already at the bottom and the second was on his way down."
A pair of skiers were ascending the east-face of Alex Lowe Peak when they triggered an avalanche that broke 150' above them. One skier was caught and carried 250 vertical feet. No one was injured or buried.
A pair of skiers were ascending the east-face of Alex Lowe Peak when they triggered an avalanche that broke 150' above them. One skier was caught and carried 250 vertical feet. No one was injured or buried. Photo: Anonymous