<p>A foot of new snow (0.9-1.4” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</a>) since Saturday morning and strong winds added a big load to a weak snowpack. Across the southern ranges, the lower snowpack consists of 1.5’ of weak, sugary facets on the ground (<strong><a href="https://www.mtavalanche.com/images/19/poor-structure-s-madison-range">p…;). Over the last week, Doug and I found this poor structure on Lionhead Ridge (<strong><a href="https://www.youtube.com/watch?v=hugZzlbqGqg&t=0s&list=PLXu5151n…;), and Eric and Alex found it across the southern Madison Range (<strong><a href="https://www.youtube.com/watch?v=fXzzClQFS5s&t=0s&list=PLXu5151n…;, <strong><a href="https://www.youtube.com/watch?v=l0aklSLqYaM&list=PLXu5151nmAvRNl9ku…;, <strong><a href="https://www.youtube.com/watch?v=zj26vpS2WE0">video</a></strong>).</p>
<p>Snowmobilers riding near Lionhead yesterday saw a natural avalanche and remotely triggered two other slides (<a href="https://www.mtavalanche.com/node/19607">details</a>, <a href="https://www.mtavalanche.com/images/19/lionhead-avalanche">photo</a>). The slides broke 1-2’ deep and one was triggered by the 6<sup>th</sup> rider as they passed below a small, steep slope. These natural and human-triggered avalanches show that this weak snowpack has now been pushed to its breaking point. Avoid riding on steep slopes and also stay well out from under them, as you could trigger a slide from below. The avalanche danger today is CONSIDERABLE.</p>
<p>Almost a foot of new snow (0.8” <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</a>) has fallen in the mountains near Cooke City since Sunday morning. Strong winds from the southwest to northwest built thick slabs on wind loaded slopes where natural avalanches are possible and these fresh drifts of snow will be easy to trigger. There are also weak layers buried 1-2’ deep (<strong><a href="https://www.youtube.com/watch?v=W6iS9ManzPo&t=0s&list=PLXu5151n…;) and in areas where the new snow fell on a generally shallow, weak snowpack (<strong><a href="https://www.youtube.com/watch?v=4Vb2Y4UZJ1Q&t=0s&list=PLXu5151n…;). Avalanches may break deeper, and wider, on these weak layers. Simply steer clear of steep, wind loaded slopes. Avalanches on these deeper weak layers are also possible on non-wind loaded slopes, dig down to look weak snow lower in the pack before committing to any steep slopes.</p>
<p>Today, avalanches are easy to trigger on wind loaded slopes and avalanche danger is <strong>CONSIDERABLE</strong>. On all other slopes, the avalanche danger is <strong>MODERATE</strong>.</p>
<p>While the couple inches of new snow and west winds yesterday formed some small, thin wind slabs, more deeply buried weak layers are our primary concern. Weak, sugary snow formed in early December and is now buried 1-2’ deep. We’ve received reports of avalanches or large collapses on these layers almost every day this past week (<strong><a href="https://www.mtavalanche.com/weather/wx-avalanche-log">Activity log</a></strong>, <strong><a href="https://www.mtavalanche.com/images/19/collapse-and-crack-road-cut">phot…;, </strong><strong><a href="https://www.mtavalanche.com/images/19/skier-triggered-avalanche-middle-…;, <strong><a href="https://www.mtavalanche.com/images/19/avalanche-near-throne">photo</a><…;). Yesterday, Alex went to investigate an avalanche triggered by a snowmobiler on Saturday, near Ross Peak. He found a 2’ thick hard slab resting over weak snow that remained reactive in stability tests (<a href="https://www.youtube.com/watch?v=EVCMgc_z3wA&index=2&list=PLXu51…;
<p>Although it’s been a week since the last significant snowfall, don’t get lulled into complacency. Triggering an avalanche remains a distinct possibility today. Keep a watch for obvious signs of instability (cracking, collapsing, and recent avalanches), and cover your bases by taking the time to dig before committing to steep terrain. The avalanche danger today is <strong>MODERATE.</strong></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>, email (<a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a>), phone (406-587-6984), or Instagram (#gnfacobs).</p>
On Saturday, a skier was killed in an avalanche during an avalanche safety course in southern Colorado. All six members of the group were caught in the avalanche. A preliminary report is available HERE.
Snowmobilers near lionhead witnessed three avalanches on Jan 7, 2019. One natural and two remotely triggered.
From email: "We had been climbing a safe slope adjacent to this slide... 24 inch crown and about 200 feet wide... Occurred at 1:38PM on an easterly wind loaded slope...The third slide... was triggered when the group passed below a short steep slope. We were well spaced and using safe practices when the number 6 sled in line remote triggered the avalanche. It flowed across our tracks and was about 12 inches deep. No one was caught or threatened.... on a southeast aspect."
Avalanche triggered remotely by a snowmobiler near Lionhead Ridge on January 7, 2019. From email "24 inch crown and about 200 feet wide... on an easterly wind loaded slope"
Snowpit in the crown of an avalanche that occurred on Saturday (1/5) near Ross Peak. Likely triggered by a snowmobiler as they rode downhill on an adjacent slope. link below for more details. Photo: GNFAC
From email "We found really unstable snow, slopes settling on the faceted ground layer and shooting cracks propagating across the smallish open snowfields between tree clumps. It was really scary. We turned around about 100' below the ridge and cautiously skied out the way we'd skinned up.... 300' below the ridge... On one open slightly steeper section my two partners heard whoomping (after I crossed the slope)."
