Natural wind slab that broke after 3-4 feet of new snow over 6 days. Photo: B. VandenBos
Overnight temps in single digits F.
<p>Over the past week the mountains near Bozeman, Big Sky and Cooke City got 3-5 feet of snow equal to 3-6” of <strong><a href="http://www.or.nrcs.usda.gov/snow/about/swe.html">snow water equivalent</a></strong> (SWE), and near West Yellowstone got 2 feet of snow equal to 2” of SWE. Yesterday, skiers at Bridger Bowl and in Hyalite saw small natural avalanches that broke 6-8” deep in the storm snow (<strong><a href="https://www.mtavalanche.com/node/18988">details</a></strong>, <strong><a href="https://www.mtavalanche.com/node/18989">details</a></strong>). Big Sky ski patrol triggered a large hard slab avalanche with a large explosive. It broke 3 feet deep and ran on the crust that formed prior to the recent week’s storm (<strong><a href="https://www.mtavalanche.com/node/18990">details</a></strong>).</p>
<p>Doug and I toured near Bridger Bowl the last couple days and found mostly good stability within the new snow, and between the new snow and old snow (<strong><a href="https://www.youtube.com/watch?v=R-pDJgVBPQI&list=PLXu5151nmAvRNl9ku…;, <strong><a href="https://www.mtavalanche.com/images/18/bridger-snowpit">photo</a></stron…;). However, as shown by the avalanche activity yesterday, it is important to be cautious of wind loaded slopes and avalanches breaking in the new snow for a couple days. Wind has been light for the past 24 hours, so there is plenty of fresh snow still lying around to form fresh drifts when wind speeds increase.</p>
<p>Watch for blowing and drifting snow and avoid steep, wind loaded slopes if you see cracking of fresh drifts. If you plan to ride in avalanche terrain, it is a good idea to dig to the ground and do a quick stability test. It will yield valuable information and give you an extra couple minutes to check your travel plan.</p>
<p>We are preparing for winter, scheduling avalanche classes, and setting up weather stations. If you get outside send us an observation via our website, email (<u><a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a></u>), phone (406-587-6984), or Instagram (#gnfacobs).</p>
Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar.
TONIGHT!!!, 1-hr Avalanche Awareness, 6-7pm at REI Bozeman
November 8, 1-hr Avalanche Awareness, 6-7pm at Langford Hall at MSU
November 8, 1-hr Side-country Avalanche Awareness, 6-7pm at PHD Skis
"We triggered a large avalanche in the Cirque with a 5lb. shot dangled from the Tram. The slide broke 3’ deep and took out the Dobies, Cron’s and part of the Ramp Shot avalanche paths. Hard slab- 1F minus generally. Storm slab from the past 8 days. The slide ran on a crust that formed from the left over snow from mid- October that got warmed in the 3rd week of October. The weak layer was just a thin layer of lower density snow trapped under the hard slabs- didn’t seem to be particularly faceted. Some grauple. The crust is not very hard or slick, about 2cm thick, and crumbled easily in hand... The slide had good propagation and the crown was at least 300’ long- impressive debris pile." -Big Sky Ski Patrol
Natural avalanche activity was widespread in Hyalite on Tuesday 11/6. Obs from e-mail: "The newest snow (about 18", I'd guess past 48hrs) is touchy soft slab. The top 8 inches also exhibit a storm slab-like quality. There appears to be a very slight density change between the two. Top 8" fracture and propagate cracks readily on gentle terrain, whereas in steeper terrain, the deeper slab (again, about 18" down) was propagating as I was skinning up the headwall in the steep creek drainages and steeper features nearby. Lots of natural activity on steeper terrain, but vis was limited.
Natural avalanche activity was widespread in Hyalite on Tuesday 11/6. Obs from e-mail: "The newest snow (about 18", I'd guess past 48hrs) is touchy soft slab. The top 8 inches also exhibit a storm slab-like quality. There appears to be a very slight density change between the two. Top 8" fracture and propagate cracks readily on gentle terrain, whereas in steeper terrain, the deeper slab (again, about 18" down) was propagating as I was skinning up the headwall in the steep creek drainages and steeper features nearby. Lots of natural activity on steeper terrain, but vis was limited.
