22-23
Widespread buried Surface Hoar
Today we had a question that needed answering: What is the distribution of the surface hoar? We dug in 5 places on different aspects and elevations and the answer was, “Everywhere.” But the SH is small and you can’t see it in the pit wall. It is buried about 20-35 cm deep. It will need more weight on it to get it to go. If a person was not looking for it it would be hard to find without an ECTP or Q1 fracture. I’m worried about areas with a slightly beefier slab, like what we found in Henderson Bench yesterday. Propagation and human triggering seems possible in these spots, but they are few in number. We found some thin spots and felt the sled bog down in the facets, which is issue #2. Triggering avalanches from thinner areas is still on our radar and may be for most of the winter.
GNFAC Avalanche Forecast for Wed Jan 11, 2023
<p><span><span><span><span><span><span>The mountains around West Yellowstone got a foot of new snow since Sunday. This load was added incrementally, but last night's snowfall and more falling today will elevate the avalanche danger. A weak layer of surface hoar (feathery crystals) is buried a foot under the surface and is likely to be triggered. Weak layers of sugary facets deep in the snowpack could also be triggered from either thinner spots where it's easier to impact this layer or from a smaller avalanche. Dave explains the layering in his </span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=ECi646U0Rtg"><span><span><span><strong>…; from Monday. Today is a day to avoid avalanche terrain. Whumpfing or collapsing of the snow and recent avalanches are clear signs of the widespread danger. For today the avalanche danger is rated CONSIDERABLE on all slopes.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>The southern Madison and southern Gallatin Ranges and the mountains around Cooke City have weak layers of snow that could avalanche. The most sensitive is a layer of feathery surface hoar crystals buried up to a foot deep. Yesterday, we found it breaking easily in Cooke City (</span></span></span></span></span></span><a href="https://youtu.be/7BS-6onztVI"><span><span><span><strong><span><u><span>…;) and on Monday Dave got similar results in Taylor Fork (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=ECi646U0Rtg"><span><span><span><strong>…;). The good news is that it is shallowly buried and easy to find with stability tests. The bad news is that it is sensitive, not found everywhere, and may not be visible to the naked eye. This layer is our primary concern right now, but weaker snow lower in the snowpack is also worrisome, especially around Cooke City where natural and human triggered slides are still occurring. Our </span></span></span></span></span></span><a href="http://www.mtavalanche.com/weather/wx-avalanche-log"><span><span><span>… and Avalanche Log</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span> and </span></span></span></span></span></span><a href="http://www.mtavalanche.com/avalanche-activity"><span><span><span><span>… Activity</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span> pages have details. Recent activity and poor stability test scores are evidence that it is possible to trigger avalanches today. At a minimum, dig and test for the surface hoar. If you get into avalanche terrain, stack the deck in your favor and only expose 1 person at a time and carry essential rescue gear (beacon, shovel, probe). For today the avalanche danger is rated MODERATE on all slopes.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>The mountains around Bozeman and Big Sky have not gotten much snow, but they had human triggered avalanche activity over the weekend around Big Sky (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/27587"><span><span><span><strong><span… Yellowmule</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/27582"><span><span><span><strong><span… sidecountry</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span> and </span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/23/snowboarder-caught-small-slide"><… Ridge</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>), and on Friday a large avalanche on </span></span></span></span></span></span><a href="http://www.mtavalanche.com/node/27536"><span><span><span><strong><span>… Peak</span></span></u></span></strong></span></span></span></a><span><span><span><strong><span><span> </span></span></strong></span></span></span><span><span><span><span><span><span>was likely triggered by skiers kicking a cornice. Avalanche activity along with a poor snow structure (weak layers tenuously supporting denser slabs) mean it's still possible to trigger avalanches (</span></span></span></span></span></span><a href="https://youtu.be/D38XfiTnFwU"><span><span><span><strong><span><u><span>…’s video</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span> from the Bridger Range). The weekend’s activity is recent enough to serve as a warning. Lives can be saved by carrying rescue gear and traveling one at a time in avalanche terrain. The avalanche danger is rated MODERATE. </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Please share avalanche, snowpack or weather observations via our</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/add/snow_obs"><span><span><span><span>…; </span></span></span></span></span></span><span><span><span><strong><span><u><span><span>website</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, email (</span></span></span></span></span></span><span><span><span><strong><span><span>mtavalanche@gmail.com</span></span></strong></span></span></span><span><span><span><span><span><span>), phone (406-587-6984), or Instagram (#gnfacobs). </span></span></span></span></span></span><span><span><span><span><span><span> </span></span></span></span></span></span></p>
<p>The mountains around West Yellowstone and Island Park got a foot of new snow since Sunday. This load was added incrementally, but last night's snowfall and more falling today will elevate the avalanche danger. Yesterday sledders triggered a slide near Mt. Jefferson. Today is a day to avoid avalanche terrain. Whumpfing or collapsing of the snow and recent avalanches are clear signs of the widespread danger.</p>
Upcoming Avalanche Education and Events
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Snowmobiler Triggered slide Island Park
From Facebook: High Mountain Adventures snowmobile rental reported one of their renters triggered a slide on the waterfalls (Mt Jefferson/Sawtelle).
Snowmobiler Triggered slide Island Park
From Facebook: High Mountain Adventures snowmobile rental reported one of their renters triggered a slide on the waterfalls (Mt Jefferson/Sawtelle).
Snowboarder triggered avalanche, E Republic
Snowboarder triggered this slide on a rollover on East Republic. Reportedly ran 80' wide, 1-1.5' deep. No one was caught.
Snowboarder triggered this slide on a rollover on East Republic. Reportedly ran 80' wide, 1-1.5' deep. No one was caught.
Photo attached of a fresh natural avalanche, just south of Cooke City today. It appears to have run last night or this morning. (photographed at noon)
It's on a NE aspect, about 8100', directly above the ice climb known as 'Silver Gate Center'. I'd estimate the crown to be about 10" deep and 30' wide.
Forecast link: GNFAC Avalanche Forecast for Wed Jan 11, 2023