19-20

<p>Since Wednesday night the mountains near West Yellowstone, the southern Gallatin and the southern Madison range received 12-14” of snow equal to 1.2” of <u><a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</a></u> (SWE). Last week Dave and I were at Lionhead and found a shallow, sugary, weak snowpack that will struggle to support this heavy new snow (<strong><a href="https://www.mtavalanche.com/images/19/shallow-weak-snowpack-lionhead">p…;, <u><strong><a href="https://youtu.be/i6DWvLU0Eks">video</a></strong></u&gt;). Today, avalanches are easy to trigger, will be large and destructive, and can be triggered from low angle terrain below or adjacent to steep slopes.</p>

<p>Snowfall is forecast to end this morning and wind will be calm, so natural avalanche activity is not expected to be widespread. However, the snowpack is fragile and needs only the weight of a person to trigger a large slide. See <u><strong><a href="https://youtu.be/VOudepXmDeY">Episode 2</a></strong></u> of Dashboard Talks for Dave and Doug’s discussion of the unstable snowpack at Lionhead. Avalanche danger is <strong>CONSIDERABLE</strong>. Avoid travel on or underneath steep slopes.</p>

<p>The mountains near Bozeman, Big Sky and Cooke City have a deeper and generally stable snowpack below the new snow. Earlier this week, Doug and Dave were in Cooke City and found a snowpack that lacks widespread buried weak layers (<strong><a href="https://www.youtube.com/watch?v=6O2DFTnHPcw&amp;list=PLXu5151nmAvSbcbVf…;, <strong><a href="https://www.youtube.com/watch?v=ngLsPMwRmfQ&amp;list=PLXu5151nmAvSbcbVf…;, <strong><a href="https://www.mtavalanche.com/sites/default/files/styles/very_large_1200w…;), and we received similar reports from skiers in Hyalite and the Bridger Range.</p>

<p>Today avalanches will involve the 5-8” of low density snow (0.3-0.7” SWE) that fell since Wednesday. This snow will be most unstable where light to moderate winds drifted it into stiffer slabs.</p>

<p>Yesterday skiers in Hyalite reported a weak interface below the new snow (<strong><a href="https://www.mtavalanche.com/images/19/new-snow-instability-hyalite">pho…;), and on Thursday skiers in Cooke City saw thin, wide avalanches which indicate a potential weak interface (<strong><a href="https://www.mtavalanche.com/images/19/surface-instabilities-cooke">phot…;). Dig and do a quick stability test to look for weak layers directly below the new snow. If you find unstable results, poor structure, or see cracks shooting out from your skis, then find lower angle terrain to ride. Today, new snow makes avalanches possible to trigger and avalanche danger is rated <strong>MODERATE</strong>.</p>

<p>Please send us your observations (no matter how brief) of avalanches, snow structure and stability, or new snow amounts and wind effects. You can fill out an <u><strong><a href="https://www.mtavalanche.com/node/add/snow_observation">observation form</a></strong></u>, email us (<u><strong><a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a></strong></u&gt;), leave a VM at 406-587-6984, or Instagram (#gnfacobs).</p>

<p>For those of us inclined to take a pass on Black Friday and instead indulge in White Friday, you’ll be much happier because of it. The northern mountains got a light covering of snow (.1” <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</a>) with Cooke City getting 3-4” (.3” SWE). Although far apart, the mountains have similarities: 2-3 feet of snow with good stability. Buried layers of facets and crusts that formed in the last 2 months are strong enough to support today’s snowfall. However, the new snow will be prone to avalanche at the snow surface where crusts or weak snow are found (<strong><a href="https://www.mtavalanche.com/snowpits">snowpits</a></strong&gt;). Dave and I had this concern in Cooke City (<strong><a href="https://youtu.be/6O2DFTnHPcw">video</a></strong&gt;) and yesterday a skier saw tiny slides (<strong><a href="https://www.mtavalanche.com/images/19/surface-instabilities-cooke">phot…;) which indicate that bigger avalanches will be possible with more snow. Stick to lower angled terrain if you see avalanches or find cracks shooting out from your skis or sled.</p>

<p>The snowpack in the southern Madison, southern Gallatin and mountains around West Yellowstone is weak and unstable. Since Wednesday night the mountains have gotten 6-10” of snow that measures .5”-.9” <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</a>. Yesterday and today’s snowfall are creating dangerous avalanche conditions. I expect a skier or sledder could trigger an avalanche breaking at the ground. Last week Alex and Dave found a shallow snowpack (6-18”) made entirely of sugary, very weak snow which is now ripe to avalanche (<u><strong><a href="https://youtu.be/i6DWvLU0Eks">video</a></strong></u&gt;). Traveling in the backcountry today is not recommended. Dave and I discuss the avalanche potential in Lionhead in <u><strong><a href="https://youtu.be/VOudepXmDeY">Episode 2</a></strong></u> of our Dashboard Talks.</p>

<p>We will begin issuing danger ratings soon. We are still gathering snowpack data and welcome your observations, no matter how brief. You can fill out an <u><strong><a href="https://www.mtavalanche.com/node/add/snow_observation">observation form</a></strong></u>, email us (<u><strong><a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a></strong></u&gt;), leave a VM at 406-587-6984, or Instagram (#gnfacobs).</p>