18-19

<p>The mountains south of Big Sky to West Yellowstone are getting snow and strong winds, a one-two punch that will keep avalanche conditions dangerous. A couple feet has fallen over the last 5 days and westerly winds have drifted snow into thick drifts which are ripe to avalanche. Last Thursday, Alex and I saw avalanches in Lionhead (<strong><a href="https://www.mtavalanche.com/node/20024">details</a></strong&gt;) that broke near the ground and were large. Slopes that have not avalanched yet, may be approaching their breaking point with today’s snowfall. <u>Stay clear of avalanche terrain</u>. Avalanches can be triggered from flat areas at the bottom of slopes making travel especially dangerous. For today, both natural and human triggered slides are on the menu and the avalanche danger is rated CONSIDERABLE on all slopes.</p>

<p>The mountains around Cooke City are getting snow and wind. They received a foot of snow in the last two days and will receive at least that in the next 24 hours. The main concern is wind-loaded slopes on many aspects an elevations. I had cracks shooting out in thin wind drifts on Monday, and yesterday skiers saw small wind drifts that avalanched (<strong><a href="https://www.mtavalanche.com/images/19/small-natural-avalanche">photo</a…;). These drifts will be more numerous, thicker and touchier today.</p>

<p>The snowpack is strong and stable in many areas (<strong><a href="https://www.mtavalanche.com/images/19/more-it">photo</a></strong&gt;, <strong><a href="https://www.mtavalanche.com/images/19/rasta-snowpit-profile">snowpit</a…;), yet unstable in a few others. Weak layers mid-pack, and near the ground in shallow areas have the potential to avalanche as evidenced by Saturday’s snowmobiler triggered slide on the south face of Mt. Abundance (<u><strong><a href="https://www.mtavalanche.com/node/20037">details and photos</a></strong></u>). For today, the avalanche danger is CONSIDERABLE on wind-loaded slopes and MODERATE on all others.</p>

<p>The northern ranges have no new snow, but I anticipate that will change this morning. Wind, on the other hand, is plentiful. In Hyalite, southwest winds are gusting over 50 mph. Wind-drifts will be found at many elevations and aspects and I anticipate a skier or rider could trigger one. &nbsp;In areas with shallower snowpacks (4 feet or less) there are still sugary facets in the lower half. &nbsp;Although we have not seen avalanches on this layer in two weeks, it remains a concern as Ian outlined in his <strong><a href="https://www.youtube.com/watch?v=6pL0K8aaJjI&amp;t=0s&amp;list=PLXu5151n…; on Buck Ridge. Skiers on Little Ellis yesterday saw no signs of instability, but still notched back their plans when the facets broke in their tests 1.5 feet above the ground. For today the danger is rated MODERATE on wind-loaded slopes and LOW on all others.</p>

<p>Touchy slabs of wind drifted snow sit over a weak snowpack in the southern ranges. <strong><a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</a></strong> (SWE) totals range from 1” to 1.4” since Friday. While most of that snow fell over the weekend, southwest winds increased yesterday accelerating transport onto wind-loaded slopes. Fresh drifts are 2-3’ thick and can be triggered by the weight of a single skier or rider.</p>

<p>Avalanches can also break on weak layers buried 2-4’ deep (deeper on wind-loaded slopes). There were a number of avalanches on these weak layers in the middle of last week (<strong><a href="https://www.mtavalanche.com/images/19/avalanches-lionhead-ridge">photo<…;, <strong><a href="https://www.youtube.com/watch?v=xlsoevxJbKc&amp;index=2&amp;list=PLXu51…;, <strong><a href="https://www.mtavalanche.com/node/20024">details</a></strong&gt;). Some of these slides broke near the ground, taking out the entire season’s snowpack. Avalanches breaking this deep can produce a huge amount of debris, even on relatively small slopes. A slide on Saturday in the Centennial Range that only ran 50’ vertical feet (<strong><a href="https://www.mtavalanche.com/node/20032">link to video</a></strong>, <strong><a href="https://www.mtavalanche.com/images/19/snowmobile-triggered-avalanche-ce…;) fully buried a rider and his snowmobile (<strong><a href="https://www.mtavalanche.com/images/19/snowmobile-being-dug-out-centenni…;), reinforcing the dangers of small slopes. You can trigger these slides from flat terrain beneath steeper slopes. Stay well out from under steep slopes, especially where there is a gully, trees, or other terrain trap below. Triggering an avalanche is likely and the avalanche danger is CONSIDERABLE.</p>

<p>Four inches of new snow fell near Cooke City overnight, accompanied by strong southwest winds. The new snow is dense, equaling 0.6” of <strong><a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2…;. &nbsp;While riding near Cooke City yesterday&nbsp;Doug found hard, thin drifts of wind drifted snow were cracking beneath him. These drifts will be both thicker and more reactive today. You can easily trigger an avalanche on steep, wind-loaded slopes. Steer clear of slopes with thick drifts of windblown snow to avoid this possibility. The snowpack is generally getting both deeper and stronger (<strong><a href="https://www.mtavalanche.com/images/19/more-it">photo</a></strong&gt;), but there is still weak snow on some slopes that is capable of producing large avalanches. There are weak layers both mid-pack and on slopes with a shallow snowpack, weak snow near the ground. Saturday’s snowmobile triggered slide on Mt. Abundance appears to have broken on that weak snow near the ground (<strong><a href="https://www.mtavalanche.com/node/20037">details and photos</a></strong>). Before riding into steep terrain, dig down to make sure you aren’t dealing with these reactive weak layers.</p>

<p>On wind loaded slopes, triggering an avalanche is likely and the avalanche danger is CONSIDERABLE. On non-windloaded slopes, the avalanche danger is MODERATE.</p>

<p>Despite no new snow this morning, there is soft snow available for the strong winds to transport. You can trigger an avalanche today in wind drifts 1-2’ thick. Look for these drifts below corniced ridgelines, on gully walls, and downwind of tree islands. If you see cracking around you or feel hard, punchy snow, stick to lower angled slopes. Be particularly cautious on slopes where a small avalanche would have big consequences (above trees, rocks, cliffs, etc).</p>

<p>While triggering an avalanche on deeper weak layers has become unlikely, we can’t completely forget about them. Dig down 3-4 feet to look for these weak layers and assess their stability before committing to steep slopes. On wind loaded slopes, the avalanche danger is MODERATE. On non-windloaded slopes, the avalanche danger is LOW.</p>

<p>If you get out and have any avalanche or snowpack observations to share, contact us via our <a href="https://www.mtavalanche.com/node/add/snow_observation">website</a&gt;, email (<a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a&gt;), phone (406-587-6984), or Instagram (#gnfacobs).</p>