Skiers near Blackmore found the new snow to be failing at the new/old snow interface. They were able to trigger this soft slab of new snow with a ski pole whack. Photo: G. Antonioli
Snow bikers in the northern Gallatin Range "witnessed a very reactive new snow layer in all wind loaded areas." (12/30). Photo: J. Polus
Snow bikers in the northern Gallatin Range found unstable test results on the early December facet layer (12/30). "While snow biking... We dug a snow pit at 9100 ft elevation & discovered a weak layer that propagated at 28 on the ECT test about 18 inches down. The snow below that area was all loosely faceted." Photo: J. Polus
We rode into the 2nd Yellowmule of Buck Ridge and found 2 instabilities: new snow, and facets that formed in early December. The facets are buried 1.5' under the surface and broke with an ECTP24. Two weeks ago we dug in the same spot and got ECTP10. Things are slowly getting stronger, but this weekend's snowstorm may be enough to break it and avalanche. Photo: GNFAC
<p>The mountains near West Yellowstone, the southern Gallatin Range and southern Madison Range have a weak and unstable snowpack. On Friday, we toured near Hebgen Lake and found two feet of unsupportive, sugary snow on the ground (<u><strong><a href="https://www.youtube.com/watch?v=MeTYd9mOyGk&list=PLXu5151nmAvRNl9ku…;, <u><strong><a href="https://www.mtavalanche.com/images/18/shallow-weak-unstable-hebgen">pho…;). New snow and strong wind today will form unstable slabs on this weak snowpack. Natural and human triggered avalanches are likely. Large and dangerous avalanches can be triggered from flat terrain below steep slopes. Small, steep terrain can be especially deadly, like confined gullies where avalanches can pile debris many feet deep. Today, avalanche danger is rated HIGH on all slopes. Avoid all steep slopes and low angle terrain below (avalanche runout zones).</p>
<p>Since Friday, the mountains near Bozeman and Big Sky got 8-12” of low density snow equal to .4-.6” of snow water equivalent (SWE). Yesterday, strong wind drifted this snow into slabs that easily collapsed and cracked under the weight of skiers (<strong><a href="https://www.mtavalanche.com/images/18/new-snow-instability-bridgers-1">…;). More snow and wind today will increase the size of these slabs and they remain easy to trigger. This new and wind-drifted snow will not add a lot of weight to a generally strong snowpack, and avalanches breaking deeper than the new snow are unlikely. Today, avalanches are easy to trigger on wind loaded slopes which have a CONSIDERABLE avalanche danger. On non-wind loaded slopes, avalanches of new snow are possible and avalanche danger is MODERATE.</p>
<p>The mountains near Cooke City got less snow than the rest of the area, but the snowpack has buried weak layers and more snow is expected today. A layer of facets 1-1.5’ below the surface is capable of producing avalanches. Doug found this layer last week (<u><strong><a href="https://www.youtube.com/watch?v=W6iS9ManzPo&index=2&list=PLXu51…;, <u><strong><a href="https://www.mtavalanche.com/images/18/instability-near-lulu-pass">photo…;), and on Friday a snowmobiler triggered an avalanche that broke on this layer (<u><strong><a href="https://www.mtavalanche.com/images/18/snowmobiler-triggered-mt-abundanc…)</a></strong></u>. On slopes with less than three feet of snow, the snowpack is weak and sugary to the ground (<u><strong><a href="https://www.youtube.com/watch?v=4Vb2Y4UZJ1Q&index=2&t=0s&li…;). Today, avalanches are easy to trigger where new snow is drifted into fresh slabs on this weak snowpack. Avoid travel on steep wind loaded slopes today, which have a CONSIDERABLE avalanche danger. On non-wind loaded slopes avalanches are possible to trigger and avalanche danger is MODERATE. Danger will rise to CONSIDERABLE on all slopes if snowfall is heavy today.</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>
After last season's two snowmobiler avalanche fatalities on Reas Peak in the Centennial Range we created a webpage so riders could get good, relevant information regarding snowpack and avalanches.
Avalanche Warning: Lionhead, S. Madison, S. Gallatin, Centennial
Debris from an avalanche that failed during the December 27-29 storm.
Skiers observed debris below the Banana Couloir on Ross Peak from an avalanche that failed during the most recent storm cycle. Photo: G. Antonioli
