22-23
Exposed crown on Leggat mountain, Tobacco Roots
6” of powder snow on northerly aspects above 9,000’. Wet powder of diminishing depth as elevation dropped. Supportable snow underlying everything. Didn’t dig a pit.
Spooky Snowpack in the Western T-Roots
While skinning into Big Bear gulch, off Wisconsin creek, we encountered a couple of small whumphs in a flat meadow below treeline. We also encountered one instance of localized cracking within the trees, near the hollow created by a dead tree. At the top of the ridgeline there were small cornices, and we noticed significant wind loading higher up on Old Baldy mountain.
In our east facing pit, just below the Little Bear ridgeline, we found a large melt freeze crust complex near the surface, interspersed with layers of much softer snow and NSF. Below the stout crust layers, the snowpack drastically reduced in hardness, with fist hardness facets near 50cm from the ground. We had moderate CT results (CT 12 Q2 @140cm) within the crust complex, and more difficult CT results (CT 23 Q2 @30cm) within a layer of large (3mm) striated depth hoar near the ground. Our ECT test resulted in an ECTX, possibly indicating the strength of the crusts, which neither skis nor boots would penetrate through. Our ECT column did pull out of the wall as a cohesive block when we applied shear from behind. Our pit profile was submitted through Snowpilot.
Based on these observations, and the warming we believed would occur later in the day, we decided to not ski off of Old Baldy mountain, and rather took some laps at a nearby low-angle meadow.
Beehive basin
Usual spring conditions. Out farming corn snow. Saw some activity from the warming sun.
GNFAC Avalanche Forecast for Mon Apr 17, 2023
<p>Avalanche conditions change rapidly in the springtime, and we must adapt quickly to these changes. Warm daytime temperatures on Monday and Tuesday make wet snow avalanches the dominant concern. This weather yields to cooler temperatures and snowfall, increasing the danger of avalanches within the new and wind-drifted snow. On top of these, cornice fall and the chance of deeper avalanches releasing on persistent weak layers are possible.</p>
<p><strong>The Breakdown:</strong></p>
<p><strong>Wet snow avalanches</strong> <strong>-</strong> Well above-freezing temperatures and sunshine on Monday will break down superficial crusts and make wet loose avalanches possible. Move to cooler aspects if the surface snow becomes wet and sloppy. Snow and cooler temperatures will largely shut down wet snow concerns by midweek. However, be on guard if the warm spring sun starts moistening the surface even for brief periods. On Sunday, a group on the Fin near Cooke City triggered a wet snow avalanche that carried a long distance (<a href="https://www.mtavalanche.com/node/29117"><strong><span>details</span></s…;).</p>
<p><strong>Cornice Fall</strong> <strong>-</strong> These overhanging ledges of snow grew to epic proportions during the winter. They can break far back from their edge this time of year. Avoid traveling on top of them and minimize the time spent below. Cornice fall itself is dangerous, and it often triggers avalanches on the slopes below. Recent collapses occurred on <a href="https://www.mtavalanche.com/images/23/cornice-fall-mount-abundance"><st…. Abundance</span></strong></a> and in the <a href="https://www.mtavalanche.com/images/23/giant-cornice-collapse-north-madi… Madison Range</span></strong></a>.</p>
<p><strong>New and wind-drifted snow</strong> <strong>-</strong> Snowfall this week will increase the danger of avalanches within the new and wind-drifted snow. The more it snows, and the more it blows, the more dangerous conditions will get. Before the storm arrives, dry slab avalanches are possible on higher elevation slopes where the snow remains powdery. This Saturday, outside the advisory area in the Crazy Mountains, a group triggered an avalanche that broke 50’ wide and ran 1000’ on a high elevation, north-facing slope (<a href="https://www.mtavalanche.com/node/29120"><strong><span>details</span></s…;).</p>
<p><strong>Deep Slab Avalanches and Persistent Weak Layers</strong> <strong>-</strong> The recent melt-down created a thick crust on many slopes and made triggering deep slab avalanche much less likely, but they remain possible, especially on high-elevation slopes where the melt-freeze crusts aren’t as robust. Avoid this problem by choosing simple, lower-angle terrain, especially during and immediately after storms. Deep slab avalanches released during the first week of April in the Northern Madison Range (<a href="https://www.mtavalanche.com/node/29012"><strong><span>1</span></strong>…;, <a href="https://www.mtavalanche.com/node/29119"><strong><span>2</span></strong>…;), <a href="https://www.mtavalanche.com/node/29004"><strong><span>Southern Gallatin Range</span></strong></a>, <a href="https://www.mtavalanche.com/node/28949"><strong><span>Lionhead Area</span></strong></a> and <a href="https://www.mtavalanche.com/node/28900"><strong><span>Bridger Range</span></strong></a>.</p>
<p>We are updating our <a href="https://www.mtavalanche.com/weather/wx-avalanche-log"><strong><span>ava… and weather log</span></strong></a> daily and posting relevant changes to the avalanche conditions so you can track the weather and how it affects these problems. Practice the fundamentals of avalanche safety until the snow melts. Every member of a group carries a beacon, shovel and probe. Signs of instability turn us back to lower-angle terrain. Expose only one team member at a time to avalanche terrain while the rest of the group watches from a safe position.</p>
<p><span>We will issue spring snowpack and weather updates twice a week through April, and we will share relevant avalanche and snowpack information on our website and social media. If you get out, please send us your observations no matter how brief. You can submit them via our website, email (mtavalanche@gmail.com), phone (406-587-6984), or Instagram (#gnfacobs).</span></p>
Info and Reminders
Bridger Bowl Ski Area is closed, and ski patrol is no longer performing rescues and making terrain closure decisions for you (video).
Hyalite Canyon road is closed for motorized use until May 16.
Dry loose avalanche in Crazies
From Obs: "This afternoon my group triggered a dry-loose avalanche on the north face of Big Timber Peak in the Crazies. The slide was about 12 inches deep, 50 feet wide, and ran about 1,000 vertical feet. Thankfully, no one was injured. We didn’t officially measure the slope angle but we’re estimating it to be in the 38-degree zone—prime avalanche territory. The slide consisted of new snow that fell during this recent storm. It hadn’t bonded to the thick crust underneath and released during the second skier’s run."
Deep Slab S Fork Hellroaring
From Obs: "Was able to spot a deep slab avalanche from Gallatin peak, slab was at the headwaters of S Fork Hellroaring (N aspect @ 9800) Hard to tell when this released as it was a few miles away, I would estimate the crown being around 10 feet. Observed a small storm slab on a north aspect as well (1-2 foot crown). Also saw a few dozen wet slides that released earlier this week, some tearing all the way to the ground."
From obs: "Was able to spot a deep slab avalanche from Gallatin peak, slab was at the headwaters of S Fork Hellroaring (N aspect @ 9800) Hard to tell when this released as it was a few miles away, I would estimate the crown being around 10 feet. Observed a small storm slab on a north aspect as well (1-2 foot crown). Also saw a few dozen wet slides that released earlier this week, some tearing all the way to the ground." Photo: T. Saulnier
Forecast link: GNFAC Avalanche Forecast for Mon Apr 17, 2023
Wet Snow Avalanche on The Fin
From Obs: "Had some loose wet slides on the fin today just after noon. Was about 3-6” deep at the new/old snow interface. Slide was slow moving but carried farther than we thought."