Weather and Avalanche Log for Fri Apr 6, 2018
East wind is cold: 2F at Bridger @5am; 30F at Lionhead.
17-18
This slide was remotely triggered on the Throne in the northern Bridgers. It failed on an ice crust 18-20" deep on a southeast facing slope. It broke 200 ft. wide and ran 5-600 vertical feet. With more snow and wind in the forecast, it will be best to keep terrain selections conservative in the Bridgers until the new snow has time to adjust.
Forecast link: GNFAC Avalanche Advisory for Sat Apr 7, 2018GNFAC Avalanche Forecast for Sun Apr 8, 2018GNFAC Avalanche Forecast for Mon Apr 9, 2018GNFAC Avalanche Forecast for Fri Apr 13, 2018GNFAC Avalanche Advisory for Sat Apr 14, 2018GNFAC Avalanche Advisory for Fri Apr 20, 2018GNFAC Avalanche Forecast for Mon Apr 23, 2018GNFAC Avalanche Forecast for Fri Apr 27, 2018GNFAC Avalanche Forecast for Wed May 2, 2018
GNFAC Avalanche Forecast for Thu Apr 5, 2018
Snowpack and Avalanche Discussion
<p>Overnight the Bridger Range received 6-8” of high density snow totaling 1” of SWE (snow water equivalent). Fortunately, the snowpack in the Bridger Range is strong, which will keep avalanche problems confined to the new snow. The mountains around Big Sky and Cooke City picked up 3-6” totaling .3-.5” of SWE. Although not as much as the Bridger Range, it’s still enough to elevate the avalanche hazard.</p>
<p>The main problem today will be wind loaded slopes (<strong><a href="https://www.youtube.com/watch?v=I4bf_gEizsI&index=2&list=PLXu51…;). West-southwest winds gusting 30-40 mph will easily transport the new snow and form fresh wind slabs, which will be easy to trigger. Watch for wind drifted snow near upper elevation ridgelines, rock bands, and steep convex terrain features (<strong><a href="https://www.mtavalanche.com/images/18/remotely-triggered-wind-slab-nort…;). The best defense against avalanches today will be conservative terrain selections that avoid wind loaded slopes.</p>
<p>Additional concerns will be storm slabs and loose dry avalanches (sluffs) (<strong><a href="https://www.youtube.com/watch?v=l7Msb_dLZ70&index=3&list=PLXu51…;). Pay close attention to how the new snow is bonding to the old snow surface and avoid steep, consequential terrain if the new snow slides easily.</p>
<p>Today, dangerous avalanche conditions exist on wind loaded slopes which have a <strong>CONSIDERABLE</strong> avalanche danger. Non-wind loaded slopes have a <strong>MODERATE</strong> avalanche danger.</p>
<p>Yesterday, Doug and his partner rode into Carrot Basin in the southern Madison Range and found wind loaded slopes and cornices to be the primary avalanche problems (<strong><a href="https://www.youtube.com/watch?v=QNEryYa2nKI">video</a>, <a href="https://www.mtavalanche.com/images/18/behemouth-cornices">photo</a></st…;). The lack of new snow and calmer winds overnight won’t do much to increase the avalanche hazard today. However, triggering a wind slab remains a possibility, primarily on exposed upper elevation slopes. Today, watch for and avoid thick wind drifts and steer clear of large, overhanging cornices.</p>
<p>Outside of wind loaded slopes, the snowpack lacks buried weak layers and is generally stable.</p>
<p>In the mountains near West Yellowstone, human triggered slides are possible on wind loaded slopes which have a <strong>MODERATE</strong> avalanche danger. Non-wind loaded slopes have a <strong>LOW</strong> avalanche danger.</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>, email (<a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a>), phone (406-587-6984), or Instagram (#gnfacobs).</p>
Info and Announcements
Our last daily advisory will be this Sunday, April 8th. Afterward, we will issue weather and snowpack updates on Monday and Friday mornings for most of April.
Hyalite Canyon road is closed to vehicles and reopens May 16th.
Send us your observations on Instagram! #gnfacobs
Posting your snowpack and avalanche observations on Instagram (#gnfacobs) is a great way to share information with us and everyone else this spring.
These cornices at the head of Sunlight Basin in Taylor Fork are bigger than big. The snow lip is a solid 30 feet away from the true ridge crest and could easily fool a rider or skier into getting too close to the edge. We are finding similar cornices in all our ranges. As the temperatures warm these overhangs will start to lose strength. Photo: GNFAC