18-19

<p>In the Lionhead area near West Yellowstone, the southern Madison and southern Gallatin Ranges, the lower half of the snowpack is weak, sugary facets. Last week, Eric found this weak snowpack near Bacon Rind (<u><strong><a href="https://www.youtube.com/watch?v=3NMgoDNKUQg&amp;t=0s&amp;list=PLXu5151n…;) and Doug saw it near West Yellowstone (<u><strong><a href="https://www.youtube.com/watch?v=rQ7fzq4X1-4&amp;index=2&amp;t=0s&amp;li…;). Snow and wind on Friday added weight and formed unstable slabs over this weak foundation. Yesterday, skiers at Bacon Rind in the southern Madison Range heard three “whumphs” in low angle meadows when the unstable snowpack collapsed under their skis (<strong><a href="https://www.mtavalanche.com/node/19372">details</a></strong&gt;). Slopes with drifts of snow that formed from strong wind on Friday will be the most susceptible to avalanches. However, all steep slopes should be carefully assessed before riding, and avoided 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>In the mountains near Bozeman, Big Sky and Cooke City, avalanches are possible to trigger on wind loaded slopes. On Friday, 2-6” of new snow was drifted into fresh slabs by strong southwest wind (<u><strong><a href="https://www.youtube.com/watch?v=8Hp6eil66zY&amp;list=PLXu5151nmAvRNl9ku…;). These fresh slabs add weight to a layer of weak facets buried 10-12” deep on some slopes, and create an unstable structure. Avalanches were triggered on this layer on wind loaded slopes last week (<u><strong><a href="https://www.mtavalanche.com/avalanche-activity">Avalanche Activity</a></strong></u>, <u><strong><a href="https://www.youtube.com/watch?v=mJRtrBZkgtY&amp;list=PLXu5151nmAvRNl9ku…;), skiers in Hyalite got unstable test results on this layer yesterday (<strong><a href="https://www.mtavalanche.com/images/18/ectp-22-maid-mist">photo</a></str…;), and I found it near Cooke City on Thursday (<u><strong><a href="https://www.youtube.com/watch?v=u520iMxlXOQ&amp;list=PLXu5151nmAvRNl9ku…;, <u><strong><a href="https://www.mtavalanche.com/images/18/lulu-pass-snowpit-20-dec">photo</…;). Eric found this layer in the northern Madison Range yesterday, and shows<strong> <a href="https://www.youtube.com/watch?v=OTiERTNpw38&amp;index=1&amp;list=PLXu51… his video</a></strong> that below this layer the snowpack is generally strong and avalanches breaking deeper are unlikely. Today, avalanche danger is MODERATE on wind loaded slopes and LOW elsewhere.</p>