18-19

GNFAC Avalanche Forecast for Sun Dec 2, 2018

Snowpack and Avalanche Discussion

<p>The mountains got 3-5” of low density snow early yesterday morning and 3-4” a few days ago. Yesterday, skiers in Hyalite and Beehive reported 10” of light, new snow above 9,000’. Eric and I went to Saddle Peak near Bridger and found fresh drifts that easily cracked under our skis (<strong><a href="https://www.mtavalanche.com/images/18/cracking-drift-bridgers">photo</a…;, <strong><a href="https://www.mtavalanche.com/images/18/fresh-wind-slabs-saddle-peak">pho…;), which prompted us to change our plan to more conservative terrain (<strong><a href="https://www.youtube.com/watch?v=VatQQ3EreuE&amp;list=PLXu5151nmAvRNl9ku…;

<p>Today, avalanches in the recent new snow are less likely and generally small. The snowpack below the recent snow is mostly stable and lacks widespread weak layers, and avalanches deeper than the recent snow are unlikely (<u><strong><a href="https://www.mtavalanche.com/images/18/bear-basin-ne-0">photo</a></stron…;, <u><strong><a href="https://www.youtube.com/watch?v=CF0zmpxFeM8&amp;list=PLXu5151nmAvRNl9ku…;). However, it is always essential to carefully assess the snowpack and the consequences of terrain before riding steep slopes. A small avalanche can be deadly in the wrong spot. Light wind today will not create many fresh slabs, but some may linger from yesterday or form in isolated areas today. Be on the lookout for wind-drifted snow near ridgelines, edges of gullies, and below rock outcrops.</p>

<p>A generally stable snowpack with minimal wind and light&nbsp;snow&nbsp;makes avalanche danger today <strong>LOW</strong>.</p>

<p>The Lionhead area near West Yellowstone has a weak snowpack with sugary facets in the bottom half (<u><strong><a href="https://www.mtavalanche.com/images/18/shallow-weak-snowpack-lionhead">p… href="https://youtu.be/hl5lygIF7s4">video</a></strong></u&gt;). Recent snow and wind have been light, but were enough to create an unstable snowpack on some slopes. The most likely slopes to avalanche are wind loaded slopes where a thicker slab of snow rests over the weak base. Cracking and collapsing of the snowpack are clear signs the snowpack is unstable and to avoid avalanche terrain. Avalanches breaking on this sugary, weak snow could be large and wide. The best defense is to avoid riding on and below slopes steeper than 30 degrees. Today, large avalanches are possible to trigger and avalanche danger is <strong>MODERATE</strong>.</p>

<p>New this season, we added hyperlinks to the <u><strong><a href="https://www.mtavalanche.com/weather/wx-avalanche-log">Weather and Avalanche Log</a></strong></u> and a new Menu item &lt;<u><strong><a href="https://www.mtavalanche.com/avalanche-activity">Avalanches and SnowPits</a></strong></u>&gt; with information on avalanche activity and incidents.</p>

<p>If you get out and have any avalanche or snowpack observations to share, contact us via our <u><a href="https://www.mtavalanche.com/node/add/snow_observation">website</a></u&gt;, email (<u><a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a></u&gt;), phone (406-587-6984), or Instagram (#gnfacobs).</p>

Upcoming Avalanche Education and Events

Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar.

BOZEMAN

December 5, 1-hr Avalanche Awareness, 6-7 p.m. at REI, Bozeman

December 6, 1-hr Avalanche Awareness and Beacon Practice, 6:30-8 p.m. at Story Mill Park

GNFAC Avalanche Forecast for Sat Dec 1, 2018

Snowpack and Avalanche Discussion

<p>New snow instabilities are main avalanche concern today. Three to four inches of low density snow won’t be enough to overload the generally strong snowpack (<strong><a href="https://www.mtavalanche.com/images/18/bear-basin-ne-0">photo</a></stron…;, <strong><a href="https://www.youtube.com/watch?v=CF0zmpxFeM8&amp;list=PLXu5151nmAvRNl9ku…;), however, it will be enough to elevate the avalanche danger.</p>

<p>Watch for areas of wind drifted snow on slopes loaded by west-northwest winds. Fresh wind slabs will be relatively small, but sensitive to human triggers. Watch for this problem below upper elevation ridgelines, gullies and rock outcrops.</p>

<p>A secondary problem will be loose dry avalanches or sluffs in steeper terrain. The new snow is low density and will move easily once initiated. Pay attention to this problem if you’re committing to steeper, high consequence terrain. Small slides can have severe consequences, especially in a shallow early season snowpack (<strong><a href="https://www.youtube.com/watch?v=q1aqN4N6Gww&amp;list=PLXu5151nmAvRNl9ku…;

<p>New snow and wind make human triggered avalanches possible on wind loaded slopes which have <strong>MODERATE</strong> avalanche danger. Non-wind loaded slopes have a <strong>LOW</strong> avalanche danger.</p>

<p>The Lionhead area has the weakest snowpack in our forecast region. The bottom half of the pack consists of weak sugary facets (<u><strong><a href="https://www.mtavalanche.com/images/18/shallow-weak-snowpack-lionhead">p…;, </strong></u><u><strong><a href="https://youtu.be/hl5lygIF7s4">video</a></strong></u&gt;). The four inches that fell last night totaled .4” of SWE, which won’t be enough to create widespread instability, but will put the snowpack on edge. The most unstable slopes will be those that received recent wind loading. Watch for signs of instability such as cracking/collapsing and stack the deck in your favor by keeping slope angles lower than 30 degrees.</p>

<p>Today, human triggered avalanche are likely on wind loaded slopes which have a <strong>CONSIDERABLE</strong> avalanche danger. Non-wind loaded slopes have a <strong>MODERATE</strong> avalanche danger. &nbsp;</p>

<p>New this season, we added hyperlinks to the <u><strong><a href="https://www.mtavalanche.com/weather/wx-avalanche-log">Weather and Avalanche Log</a></strong></u> and a new Menu item &lt;<u><strong><a href="https://www.mtavalanche.com/avalanche-activity">Avalanches and SnowPits</a></strong></u>&gt; with information on avalanche activity and incidents.</p>

<p>If you get out and have any avalanche or snowpack observations to share, contact us via our <u><a href="https://www.mtavalanche.com/node/add/snow_observation">website</a></u&gt;, email (<u><a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a></u&gt;), phone (406-587-6984), or Instagram (#gnfacobs).</p>

Upcoming Avalanche Education and Events

Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar.

IDAHO

Today! Klim Winter Kick-Off and avalanche awareness, Rigby, Idaho

BOZEMAN

December 5, 1-hr Avalanche Awareness, 6-7 p.m. at REI, Bozeman