This avalanche was triggered on 1/16/20. The crown was measured 15' deep and was knife hardness wind slab. The slide broke on a layer of faets that is found on many slopes in our forecast area. Photo: GNFAC
From obs: "There is a small east facing basin that’s between Divide Peak and Maid of the Mist Basin. While walking along the ridge that connects the two, my partner intentionally broke off a large piece of a cornice, which then triggered two substantially sized avalanches in the basin below. The first avalanche was directly beneath the collapsed cornice with a crown 6-12 inches deep and about 30 ft across. The second avalanche was triggered by the 1st avalanche and had a crown of similar depth but was substantially larger. It was hard to see as the crown travelled uphill and around a corner. The ascpet was E and SE, at the elevation of 9,600ft. The pictures I got are poor, but should give you an idea of the size."
Photo: C. Kussmaul
From obs: "There is a small east facing basin that’s between Divide Peak and Maid of the Mist Basin. While walking along the ridge that connects the two, my partner intentionally broke off a large piece of a cornice, which then triggered two substantially sized avalanches in the basin below. The first avalanche was directly beneath the collapsed cornice with a crown 6-12 inches deep and about 30 ft across. The second avalanche was triggered by the 1st avalanche and had a crown of similar depth but was substantially larger.
We saw this big natural avalanche at noon on January 18th. It broke late on 1/17/20 or early 1/18/20 after strong wind and new snow (1" SWE) heavily loaded slopes. Photo: GNFAC
This big natural avalanche broke late on 1/17/20 or early 1/18/20 after strong wind and new snow (1" SWE) heavily loaded slopes. Photo: GNFAC
<p>New snow, strong winds, and unstable weak layers have combined to make dangerous avalanche conditions. Yesterday, Big Sky and Bridger Bowl ski patrols found the new snow avalanching easily while ski cutting during the storm. West winds drifted the new snow into cohesive slabs that will break under the weight of a skier or rider today. You will find these dangerous drifts near ridgelines and in cross-loaded gullies. Avalanches in the new snow can break 2-3 ft deep.</p>
<p>The new snow also added weight to the weak layers lower in the snowpack. Yesterday afternoon, a large natural avalanche broke down to the ground on a wind-loaded slope in the northern Bridger Range (<strong><a href="https://www.mtavalanche.com/images/20/large-slide-northern-bridgers-2">…;). Another part of this bowl avalanched 2-3 ft deep on Thursday. The additional wind-loading yesterday pushed this slope over the edge and caused it to slide as well. Avalanches starting in the new snow can step down to these weak layers becoming much larger and more dangerous.</p>
<p>The avalanche danger is CONSIDERABLE on wind-loaded slopes. On all other slopes the avalanche danger is MODERATE.</p>
<p>The mountains around West Yellowstone and near Cooke City didn’t see as much new snow. Avalanches in the new and wind-drifted snow will be shallower and mostly a concern in the steepest rockiest terrain. The larger concern is the potential to trigger a big avalanche breaking deep in the snowpack. A natural avalanche was seen yesterday on an east facing slope below Lionhead Ridge (<strong><a href="https://www.mtavalanche.com/images/20/avalanche-airplane-bowl">photo</a…;).</p>
<p>A snowmobile triggered avalanche on Henderson Mountain on Thursday broke close to 15 feet deep (<strong><a href="https://www.mtavalanche.com/node/21609">details</a></strong>) and a very large natural avalanche broke across the whole NE shoulder of Mount Fox on Tuesday (<strong><a href="https://www.mtavalanche.com/node/21601">details</a></strong>). Getting caught by one of these big slides would almost assuredly have devastating consequences. There is no practical way to test weak layers buried this deep. Patience is the only viable strategy. Give these weak layers more time to adjust and strengthen before getting onto steep slopes.</p>
<p>Large human triggered avalanches are possible and the avalanche danger is MODERATE today.</p>
<p>Non-wind-drifted slopes in the northern Gallatin Range are generally stable. Six inches of light snow yesterday has drifted into unstable pockets where you could trigger a slide. Be cautious on any slope where you find more than 6 or 8 inches of cohesive drifted snow. These fresh drifts will be easily triggered today. The avalanche danger is MODERATE on windloaded slopes and LOW on all others.</p>
<p>If you get out, please send us your observations no matter how brief. You can fill out an <strong><a href="https://www.mtavalanche.com/node/add/snow_observation">observation form</a></strong>, email us (<strong><a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a></strong>), leave a VM at 406-587-6984, or Instagram (#gnfacobs).</p>
Our education calendar is full of awareness lectures and field courses. Check it out and plan to attend one or two: Events and Education Calendar.
COOKE CITY
Every Friday and Saturday, Snowpack Update and Rescue Training. Friday, 6:30-7:30 p.m. at the Soda Butte Lodge. Saturday anytime between 10-2 @ Round Lake.
BOZEMAN
