17-18

Cornices across the advisory area are monstrous right now. They can break further back than you might expect and can also trigger slab avalanches on the slopes below. Give these a wide berth along the ridgelines and pay attention when traveling on slopes below. Photo: GNFAC 

Bridger Range, 2018-03-06

GNFAC Avalanche Advisory for Tue Mar 6, 2018

Snowpack and Avalanche Discussion

<p>A few inches of new snow (.1-.2” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</a>) with west winds will keep alive the possibility of triggering wind-loaded slopes. Wind slabs from the weekend are 1-3’ thick. On Sunday a skier triggered a small slide above Hebgen Lake (<a href="https://www.mtavalanche.com/images/18/skier-triggered-avalanche-near-he…;, <a href="https://www.mtavalanche.com/images/18/skier-triggered-avalanche-near-he…;) and we could see something similar today. Near Ross Peak in the Bridger Range a skier dug a snowpit and easily broke a 2’ thick wind slab in his stability test, a warning of avalanche potential. Most wind slabs will be found along ridgelines, but a few may lurk in mid-elevation gullies.</p>

<p>At the ridge crest, massive cornices could break from the weight of a passing skier. These are doubly dangerous as not only would you tumble off alongside a literal ton of snow, but sometimes these car-sized chunks trigger avalanches (<a href="https://www.mtavalanche.com/images/18/cornice-failure-hyalite"><strong>…;, <a href="https://www.mtavalanche.com/images/18/cornice-illustration"><strong>ill…;).</p>

<p>Alex and I were in Bacon Rind on Sunday and our only avalanche concern was new snow and wind-loading (<a href="https://youtu.be/dxyEViPcngg"><strong>video</strong></a&gt;, <strong><a href="https://www.mtavalanche.com/images/18/bacon-rind-profile-4-mar">snowpit…;). Throughout out forecast area the snowpack is generally stable and the likelihood of triggering avalanches is decreasing. Without obvious signs of instability, like a fresh avalanche, we may fool ourselves into thinking that all slopes are safe. This is why it is important to carry rescue gear and travel one at a time in avalanche terrain. These actions are our last line of defense in case we are wrong in our assessment.</p>

<p>For today, the avalanche danger is rated <strong>MODERATE</strong> on all wind-loaded slopes and<strong> LOW</strong> on all others.</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

March 7th, Avalanche Awareness, 6-7:30 p.m. @ REI

LIVINGSTON

March 20, Beer for a Cause Night at Katabatic Brewing, 4-8p.m. A dollar from every pint will be donated to The Friends of the Avalanche Center.

COOKE CITY

GNFAC Avalanche Forecast for Mon Mar 5, 2018

Snowpack and Avalanche Discussion

<p>Yesterday a cold northwest flow brought 6-14” of low density powder to the mountains near Bozeman and Big Sky, and 2-4” near West Yellowstone and Cooke City. Even where deepest, this snow equals a light .4-.6” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</a> (SWE). Eric was at Mt. Ellis yesterday and found 10” of powder was easily triggered into dry loose avalanches on steeper slopes (<strong><a href="https://youtu.be/8Yi14JLabEw">video</a></strong&gt;). Skiers in Hyalite reported soft slabs easily cracked on lower angle terrain, and ski patrols&nbsp;triggered lightweight slabs of new snow. Today, dry loose avalanches and soft slabs of new snow are possible to trigger. These slides won’t be huge, but carry enough force to push a person over cliffs, into trees or other hazards.</p>

<p>The primary avalanche problem to avoid today is drifts of snow 1-3’ deep that formed from strong west-northwest wind. These wind slabs are easy to trigger and could avalanche naturally.&nbsp;They are largest near ridgelines and possible on&nbsp;cross-loaded terrain, convex rolls, below cliffs and along edges of gullies. Avoid steep, wind loaded slopes today.</p>

<p>Wind and snow have&nbsp;formed massive cornices this season. They can easily break under the weight of a person, and new snow and wind loading could break them naturally. Avoid slopes below cornices and keep a far distance back along ridgelines (<strong><a href="https://www.mtavalanche.com/images/18/cornice-failure-hyalite">photo</a…;, <strong><a href="https://www.mtavalanche.com/images/18/cornice-illustration">illustratio…;).</p>

<p>Below the new snow, the snowpack is generally stable and deeper avalanches are unlikely. Doug and I were at Bacon Rind yesterday and found new snow and wind loading the only concern (<strong><a href="https://youtu.be/dxyEViPcngg">video</a></strong&gt;). In isolated areas, avalanches breaking in older snow are possible. This weekend, a skier triggered a small slide near Hebgen Lake that broke into snow from last week (<strong><a href="https://www.mtavalanche.com/images/18/skier-triggered-avalanche-near-he…;, <strong><a href="https://www.mtavalanche.com/images/18/skier-triggered-avalanche-near-he…;), and a skier in Hyalite reported a couple large collapses on wind affected terrain. It is always essential to carefully assess the snowpack and practice safe travel habits in avalanche terrain.</p>

<p>Today, strong wind and new snow formed slabs that are easy to trigger and avalanche danger is <strong>CONSIDERABLE</strong> on wind loaded slopes. Danger is <strong>MODERATE</strong> on non-wind loaded slopes.</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>

<div>&nbsp;</div>

Upcoming Avalanche Education and Events

Events and Education Calendar

BOZEMAN

March 7th, Avalanche Awareness, 6-7:30 p.m. @ REI

LIVINGSTON

March 20, Beer for a Cause Night at Katabatic Brewing, 4-8p.m. A dollar from every pint will be donated to The Friends of the Avalanche Center.

COOKE CITY

Skiers near Hebgen Lake reported: "...we did observe an isolated skier triggered slide on a steep, south facing, rocky rollover in the bottom of one of the trapper slidepaths that broke about 16 inches deep on an ice crust." Photo: A. Pohl 

Lionhead Range, 2018-03-05