19-20

<p>Yesterday on Lionhead Ridge near West Yellowstone skiers triggered large collapses of the snowpack on low angle terrain (<strong><a href="https://www.mtavalanche.com/images/19/widespread-cracking-lionhead">pho…;), and on Buck Ridge near Big Sky snowmobilers saw widespread natural avalanches that broke on sugary weak snow near the ground (<strong><a href="https://www.mtavalanche.com/images/19/natural-avalanches-buck-ridge">ph…;, <strong><a href="https://www.mtavalanche.com/images/19/natural-avalanche-buck-ridge-2">p…;). During yesterday’s storm the mountains near Big Sky and West Yellowstone got 8-10” of snow equal to 0.7-0.9” of <u><strong><a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</a></strong></u> (SWE). Moderate to strong westerly wind drifted this snow into thick slabs which overloaded an unstable snowpack (<u><strong><a href="https://www.mtavalanche.com/images/19/ect-near-two-top">photo</a></stro…;, <u><strong><a href="https://www.youtube.com/watch?v=AbtyS3X7glA&amp;list=PLXu5151nmAvSbcbVf…;). Today dangerous avalanche conditions exist and large avalanches are easy to trigger. The poor snowpack structure makes it possible to trigger avalanches from low angle terrain below steep slopes. Avoid travel on and underneath steep slopes. Avalanche danger is <strong>CONSIDERABLE</strong>.</p>

<p>Yesterday near Cooke City two separate snowmobilers had close calls with avalanches (<strong><a href="https://www.mtavalanche.com/node/21147">details here</a></strong>). One triggered a small slide which buried his sled (but not him) in a terrain trap and he had to be rescued. The other was near Crown Butte attempting to ascend the steep north side of Daisy Pass when a natural avalanche released and nearly missed their group. Yesterday the mountains near Cooke City got 14” of snow equal to 1.4” of SWE. Strong westerly wind drifted this heavy snow into thicker, heavier slabs which remain easy to trigger. Today, large avalanches are easy to trigger and avalanche terrain should be avoided, especially wind-loaded slopes. Avalanche danger is <strong>CONSIDERABLE</strong>.</p>

<p>The Bridger Range and Hyalite got 4-6” of new snow equal to 0.5-0.6” of SWE during yesterday’s storm. Avalanches breaking below this new snow are possible where westerly wind formed fresh drifts. Yesterday skiers in the northern Bridger Range found unstable stability test results on weak layers a foot below the snow surface (<strong><a href="https://www.mtavalanche.com/sites/default/files/styles/large/public/201…;). The new snow is not quite enough to create widespread instability on these weak layers, but it is worthwhile to search for these layers and avoid steep slopes where they exist. We are suspect of these buried weak layers on Saddle Peak where hard wind slabs formed above them (<u><strong><a href="https://www.mtavalanche.com/images/19/large-avalanche-mundys-bowl-bridg…;, <u><strong><a href="https://www.youtube.com/watch?v=mbm3kJ652Fk&amp;list=PLXu5151nmAvSbcbVf…;). Carefully assess the stability of recent snow and be extra cautious of wind loaded slopes. Today the avalanche danger is <strong>MODERATE.</strong></p>