17-18

On Tuesday, Feb 6, "Woke up this morning to a fresh deep slab avalanche that was triggered by a cornice drop sometime early this morning on east Woody Ridge.... Estimated D3.5 R4... This path has had several avalanches this season, but the crown looks to be at least 10' tall on lookers right." Photo: B. Zavora

Cooke City, 2018-02-06

GNFAC Avalanche Advisory for Tue Feb 6, 2018

Snowpack and Avalanche Discussion

<p>Cooke City (“Snow Baron of the West”) has received 4’ of snow equaling near 4” of <a href="http://www.or.nrcs.usda.gov/snow/about/swe.html"><strong>snow water equivalent</strong></a> (SWE) since Friday. Yesterday we issued an Avalanche Warning for the area because the amount and rate of snowfall was worrisome. A couple natural avalanches were seen and I expect a few more will be noticed with clearing skies (<strong><a href="https://www.mtavalanche.com/images/18/baronette-peak-avalanche">photo1<…;, <strong><a href="https://www.mtavalanche.com/images/18/ynp-avalanche-peak-9595">photo2</…;). The snowfall is tapering off and winds are light and the warning has expired, but conditions are still dangerous. The mountains will take time to fully adjust to this load and it’s likely you could trigger slides today. Four feet is a lot of snow and avalanches could be large and deep on par with the ones we saw last week (<a href="https://www.youtube.com/watch?v=cj2Qhn1ldQA&amp;list=PLXu5151nmAvQSYtIf…;, <a href="https://www.mtavalanche.com/images/18/natural-avalanche-woody-ridge"><s…;). My recommendation is to avoid avalanche terrain today. The danger is rated <strong>CONSIDERABLE</strong> on all slopes in the Cooke City area.</p>

<p>The northern Bridger Range picked up 6” of snow in the last 24 hours which is in addition to 10” the night before (<strong><a href="https://www.mtavalanche.com/weather/stations/brackett-creek-snotel-site… Creek SNOTEL</a></strong>), with half that amount falling at Bridger Bowl. Winds have calmed and snowfall has tapered off, but 1.8”of SWE is a large load. Slopes that were wind-loaded from west winds yesterday may still be triggered. Today the avalanche danger is <strong>CONSIDERABLE</strong> on all wind-loaded terrain and <strong>MODERATE </strong>elsewhere.</p>

<p>The southern mountains including the Lionhead area near West Yellowstone have a couple weak layers in the snowpack. Alex and I skied near Hebgen Lake on Sunday and got a layer of surface hoar (buried 1-2’ deep) to break in our stability test, plus weak, sugary facets broke near the ground with a few more taps of the shovel (<strong><a href="https://youtu.be/2mj4jkCkEpc">video</a></strong>,<strong&gt; <a href="https://www.mtavalanche.com/images/18/hebgentrapper-profile-4-feb">snow…;). The surface hoar has spotty distribution and the facets at the ground are not easy to trigger, so digging and testing is especially valuable to determine a slopes stability. For today, the avalanche danger is <strong>MODERATE</strong> since avalanches are still possible.</p>

<p>In the last 24 hours the mountains around Big Sky and Hyalite got another 1-3 inches of snow. I was up Hyalite yesterday and experienced swirly winds loading slopes at many elevations, not just the ridgelines. On Sunday, on Alex Lowe Peak, skiers saw the debris and crown of a wind slab avalanche in the couloir (<strong><a href="https://www.mtavalanche.com/images/18/wind-slab-avalanche-alex-lowe-pea…;). The snowpack in the northern Gallatin and northern Madison Ranges is generally strong and my main concern is triggering wind slabs (<a href="https://www.youtube.com/watch?v=-Kh4wvvQ3Wk"><strong>video</strong></a&…;). For today, the avalanche danger is rated<strong> MODERATE</strong> on wind-loaded slopes and<strong> LOW</strong> elsewhere.</p>

<p>If you get out and have any avalanche or snowpack observations to share, drop a line 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>

Upcoming Avalanche Education and Events

Events and Education Calendar

BOZEMAN

Feb. 6th, Sidecountry specific avalanche awareness for family and friends. 6-8 p.m. @ Beall Park

Feb. 7th, Woman’s specific avalanche awareness, 6-7:30 p.m. @ REI in Bozeman

Feb. 7th, Avalanche awareness, 6-7:00 p.m. @ Roskie Hall MSU

On February 4th (Sun) skiers found shallow wind slabs on northerly aspects heading up to the Blackmore/Elephant saddle in hasty tests. They observed ECTP18 failure of a wind slab at ~25cm depth in the NE bowl of Alex Lowe Peak and observed recent slide activity in and below Hellmouth couloir. It appeared a small pocket had ripped out of the couloir and a larger slab had triggered in the apron below. Photo: C. Ronemus
Northern Gallatin, 2018-02-06