17-18

<p>Yesterday, a skier triggered a small wind slab in Hyalite (<strong><a href="https://www.youtube.com/watch?v=1WzubfwJ6G4&amp;list=PLXu5151nmAvQSYtIf…;). It broke 6-12” deep, 30’ wide and occurred on an upper elevation, north facing slope. The slide was not large, but could have been dangerous if triggered in high consequence terrain. Isolated pockets of wind drifted snow are mainly confined to upper elevation slopes below ridgelines and cliff bands. The slide yesterday is a good reminder that human triggered avalanches remain possible on wind loaded slopes.</p>

<p>Cornices are also a significant problem. On Tuesday, a snowmobiler in the Centennial Range south of West Yellowstone was injured when a cornice broke under his feet, which sent him tumbling down hundreds of feet over a cliff (<strong><a href="https://www.mtavalanche.com/images/18/cornice-fallcentennial-mtns">phot…;). Click the link below for a more detailed report. Give cornices a wide distance along the ridgelines and don’t spend too much time on slopes below (<strong><a href="https://www.mtavalanche.com/images/18/cornice-drop-cooke-city">photo</a…;).</p>

<p>An additional problem today will be wet snow avalanches. Above freezing temperatures and the possibility of rain will increase the wet snow avalanche danger as the day progresses, mainly below 8,000 feet. Yesterday, a skier on Yellow Mountain near Big Sky observed an old wet loose avalanche that occurred during last week’s warm up (<strong><a href="https://www.mtavalanche.com/images/18/natural-wet-loose-avalanche-yello…;). Similar avalanches could be possible today on steep, mid to low elevation slopes. If the upper layers of the snowpack start to feel soft, damp and unconsolidated it will best to avoid steeper terrain. Rain is a sure tell sign it’s time to leave the backcountry.</p>

<p>Today, the dry snow avalanche danger is rated <strong>MODERATE</strong> on wind loaded slopes and <strong>LOW</strong> on non-wind loaded slopes. The wet snow avalanche danger will start out <strong>LOW</strong>, but rise to <strong>MODERATE</strong> on slopes below 8,000 ft.</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>Yesterday, west to southwest wind steadily increased and blew snow into 5-6” thick wind slabs. Skiers up Hyalite and around Big Sky easily triggered these with ski cuts and I expect similar results today. The snowpack is generally stable (<a href="https://youtu.be/g3PWCYf1Y9M"><strong>video</strong></a&gt;) and these soft slabs of wind deposited snow are unlikely to break into older snow. The wind slabs will be found near ridgelines where a second hazard lurks: cornices. Every range has them (<a href="https://www.mtavalanche.com/images/18/cornice-drop-cooke-city"><strong>…;) and yesterday a skier in Hyalite noted a few recently broke. The rider in the Centennial Mountains is lucky to be alive after a long fall and avalanche. Cornices this season are extra beefy and overhang far off ridges, ready to break from a passing skier or sledder. Until you’ve soiled your pants with a close call, it’s hard to appreciate how unexpected and far back cornices break.</p>

<p>Winds have lessened overnight but soft wind slabs that formed yesterday are still possible to trigger. The old snow lacks widespread weak layers and avalanches on non-wind-loaded slopes are not expected, but not impossible either. Even during times of relative stability it’s a good idea to dig and test the upper couple feet of the snowpack to confirm the new snow is sticking well to the old surface. For today, the avalanche danger is rated <strong>MODERATE</strong> on 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>

<p>One to three inches of new snow will not adversely affect the snow stability. Winds are light to moderate from the west and wind loading will be minimal. Avalanches over the weekend broke within Friday’s new snow from a density change mid-storm. Both Eric in Beehive Basin and Alex in the Bridger Range reported this, especially on wind-loaded slopes (<strong><a href="https://youtu.be/6LziSi4Boak">video</a></strong&gt;, <a href="https://www.youtube.com/watch?v=6LziSi4Boak"><strong>video</strong></a&…;). Since then it has strengthened and stabilized. I rode into Taylor Fork in the southern Madison Range yesterday and found good conditions: no signs of instability in the mountains or in my snowpit (<strong><a href="https://youtu.be/g3PWCYf1Y9M">video</a></strong&gt;). Our snowpack lacks widespread weak layers and our avalanche concerns are limited to small pockets of wind-blown snow and cornices breaking off along ridgelines (<strong><a href="https://www.mtavalanche.com/images/18/cornice-drop-cooke-city">photo</a…;).</p>

<p>Temperatures will rise above freezing in the northern mountains and possibly the south. Even a kiss of sunshine will dampen the snow surface and increase the chance of wet, loose avalanches. Clouds and light winds will keep the avalanche danger minimal if the weather forecast holds true. If skies become clear and sunny or temperatures break above 40F the wet snow avalanche danger would increase. Roller balls, pinwheels and wet sluffs of snow are signs of a weakening surface.</p>

<p>For today, throughout our advisory area, the dry snow avalanche danger is rated <strong>LOW</strong>. The wet snow avalanche danger is also rated <strong>LOW</strong>, but could rise to <strong>MODERATE </strong>if skies clear and temperatures warm more than expected.</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>