17-18

<p>The main avalanche problem today is unstable slabs that will form from new snow and wind through the day. Fresh wind slabs will be easy to trigger and found near ridgelines and along the edges of gullies. These slabs will grow larger as snow falls through the day. As snow piles up, watch for obvious signs of instability like cracking and collapsing, blowing and drifting snow, and natural avalanches. Avoid nearby, similar avalanche terrain if these signs are present. In the absence of obvious signs of instability, dig 1-2 feet deeper than the new snow and assess stability before committing to avalanche terrain.</p>

<p>Aside from new snow and wind today, the snowpack is generally stable and lacks widespread persistent weak layers. Eric went to Big Sky yesterday to look at the massive avalanche that patrol triggered with explosives on Thursday (<a href="https://www.mtavalanche.com/images/17/n-summit-slide-crown"><strong>pho…;, </strong><a href="https://www.mtavalanche.com/images/17/n-summit-slide-crown-photo-2"><st…;, <a href="https://www.mtavalanche.com/images/17/n-summit-slide-runout"><strong>ph…;). The slide broke 6-10 feet deep on a weak layer of depth hoar on a north facing slope around 11,000’. This isolated, lingering instability is an outlier within our area’s generally stable snowpack, but a reminder that avalanches are still possible (<strong><a href="https://youtu.be/6Dueob5ScfI">video</a></strong&gt;). Cornices are large right now (<a href="https://www.mtavalanche.com/images/17/wind-loading-and-large-cornices-h…;, <a href="https://www.mtavalanche.com/images/17/big-cornices-hyalite"><strong>pho…;), and they could break under the weight of a person and be a perfect trigger for a large avalanche like the one at Big Sky. Travel far back from the leeward, corniced edge of ridgelines and minimize time on slopes below them.</p>

<p>A generally stable snowpack makes avalanche danger <strong>LOW</strong> this morning. Heavy snowfall and moderate wind today will form unstable slabs that are easy to trigger, and avalanche danger will increase to <strong>MODERATE</strong> this afternoon.</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>

<p>The snowpack throughout our advisory area is generally stable and lacks widespread persistent weak layers (<strong><a href="https://www.mtavalanche.com/snowpits">snowpits</a></strong&gt;). With no more than a couple inches of new snow today avalanches are not likely. Wind slabs that formed from new snow and wind earlier in the week have gained strength and are hard to trigger today. However, these slabs may still be found near ridgelines, below cornices, or along the edges of gullies. Approach this terrain with caution and consider the consequences of being caught in any size slide. Very small fresh wind slabs may form by this afternoon if a few inches of snow fall today.</p>

<p>Cornices are impressive in size right now and hang far off the leeward edge of ridgelines (<strong><a href="https://www.mtavalanche.com/images/17/wind-loading-and-large-cornices-h…;, <strong><a href="https://www.mtavalanche.com/images/17/big-cornices-hyalite">photo</a></…;). These massive blocks of snow could break under the weight of a skier or snowmobiler. Though not likely, a cornice could be the perfect trigger for a large avalanche like the one triggered by Big Sky Patrol a couple days ago (<strong><a href="https://www.mtavalanche.com/images/17/n-summit-slide-crown">photo</a&gt;, <a href="https://www.mtavalanche.com/images/17/n-summit-slide-crown-photo-2">pho…;, <strong><a href="https://www.mtavalanche.com/images/17/n-summit-slide-runout">photo</a><…;). Travel far back from the leeward, corniced edge of ridgelines and minimize time on slopes below cornices.</p>

<p>The massive avalanche triggered by Big Sky patrol shows the isolated potential to trigger a deep slab on old, weak snow from September and October. This type of avalanche is not likely, but the right trigger in the right place today might trigger a slide. Practice safe backcountry travel. Carry rescue gear and expose no more than one person at a time to avalanche terrain. Today, a generally stable snowpack and minimal recent snow makes the avalanche danger <strong>LOW</strong>.</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>