18-19
From email: "7,500' West facing in the Hellroaring Drainage 12/22/18"
Photo: S. Hansen
Hellroaring Drainage; "Huge whoomphs"
"I was in the Hellroaring Drainage Yesterday, snow depths below 7,000' hover around 18", around 8,000' snow depths increase significantly but are still shallow i.e. less than 30". Witnessed the largest "whoomphs" I have ever felt (that's saying something since last Decemeber/Jan was horrendous), interestingly much of this was felt returning on the same skin track, telling me this is a stubborn layer that may not give right away. The largest was a collapse in a meadow nearly 0.25 miles long."
Saddle Peak is backcountry terrain located south of Bridger Bowl ski area's boundary. Hazards are not mitigated by patrol and there are no patrol rescue services. You should have the necessary skills and knowledge about snowpack and safe travel before entering this terrain. Photo: GNFAC
Small snowmobile triggered slide Buck Ridge
About an 8 inch slab triggered by snowmobilers. South facing slope in the 3rd yellowmule at buck ridge.
From e-mail on 12/23: "About an 8 inch slab triggered by snowmobilers. South facing slope in the 3rd yellowmule at buck ridge." Photo: Crisman
GNFAC Avalanche Forecast for Mon Dec 24, 2018
<p>In the mountains near West Yellowstone and the southern Madison and Gallatin Ranges the lower half of the snowpack is weak, sugary facets. Eric found this weak snowpack last week near Bacon Rind in the southern Madison Range (<u><strong><a href="https://www.youtube.com/watch?v=3NMgoDNKUQg&t=0s&list=PLXu5151n…;) and Doug saw it near West Yellowstone (<u><strong><a href="https://www.youtube.com/watch?v=rQ7fzq4X1-4&index=2&t=0s&li…;). Recent snow and wind have formed unstable slabs of snow on top of this weak foundation. On Saturday, Skiers at Bacon Rind heard three “whumphs” when they collapsed the unstable snowpack in low angle meadows (<u><strong><a href="https://www.mtavalanche.com/node/19372">details</a></strong></u>).</p>
<p>A few inches of snow this morning will get drifted into fresh slabs and add weight to the unstable snowpack. Slopes will be most unstable during new snow and wind loading. Be extra cautious of steep, freshly wind loaded slopes today. Avoid steep slopes if they have a thick slab of snow resting on weak, sugary facets. Today, avalanches are possible to trigger and avalanche danger is MODERATE.</p>
<p>The mountains near Bozeman, Big Sky and Cooke City have a 2-4’ deep and mostly stable snowpack. The exception is slopes where recent snow was drifted into thick slabs over a weak layer of facets or surface hoar buried 8-12” deep. Minimal recent snow and wind loading makes these slabs more difficult to trigger, but it remains possible. A few inches of new snow this morning will be drifted into fresh wind slabs that will be easy to trigger. These fresh slabs will likely be small and add relatively little stress to a generally strong snowpack.</p>
<p>Carefully assess wind loaded slopes today and consider the consequences of even small slides. Yesterday, Doug and I went to Saddle Peak and found a mostly strong snowpack, but there were hard wind slabs on the surface scattered around the mountain (<strong><a href="https://www.youtube.com/watch?v=2lO7K1Y-gOs&list=PLXu5151nmAvRNl9ku…;). Eric and my recent videos from near <strong><a href="https://www.youtube.com/watch?v=OTiERTNpw38&index=1&list=PLXu51… Sky</a></strong> and <strong><a href="https://www.youtube.com/watch?v=u520iMxlXOQ&list=PLXu5151nmAvRNl9ku… City</a></strong> also show the main instabilities are in the top 8-12” of an otherwise generally strong snowpack. Today, it is possible to trigger small wind slabs and avalanches on facets 8-12” deep, and avalanches deeper than that are unlikely. Avalanche danger is MODERATE on wind loaded slopes and LOW on non-wind loaded slopes.</p>
<p>If you get out and have any avalanche or snowpack observations to share, contact us via our <u><a href="https://www.mtavalanche.com/node/add/snow_observation">website</a></u>, email (<u><a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a></u>), phone (406-587-6984), or Instagram (#gnfacobs).</p>
Snowmobiler Avalanche Fatality in the Wyoming Range, Wyoming
From Bridger-Teton Avalanche Center (12/24): “A snowmobiler died two days ago in the Wyoming Range after triggering a small slab avalanche and getting pinned beneath his sled.” Check the BTNFAC website or avalanche.org for updated details. Our condolences go out to those involved.
Weather and Avalanche Log for Mon Dec 24, 2018
Trace near Bozeman/Big Sky
Riders in Cooke City observed wind loading near ridge tops and cross-loading at middle elevations today. They also reported multiple small wind slabs releasing near Lulu Pass during the day on Friday. P: L. Zuckiewicz
Forecast link: GNFAC Avalanche Forecast for Mon Dec 24, 2018GNFAC Avalanche Forecast for Tue Dec 25, 2018
Small Slab Avalanches Near Lulu Pass
Riders triggered avalanches on wind-loaded slopes that were 20-100 feet wide near Lulu pass.