From obs.: "This slide appeared to have happened a few days prior to when we observed it on the 16th. When we skied the skiable terrain at Dudley Creek the snowpack was stable, though snow coverage was thin." Photo: A. Pessl
Fresh drifts broke naturally along the ridgeline which became long running wet slides. 4/17/20. Photo: GNFAC
Fresh drifts broke naturally along the ridgeline which became long running wet slides. 4/17/20. Photo: GNFAC
GNFAC forecaster observed many wet loose slides entraining recent snow from Bridger Peak through the Throne. There were also fresh drifts along the ridgeline that broke naturally and became long running wet loose slides. Slide sizes ranged D1-D2.
From obs email (4/17/20): "5(?) slides into North Bowl (the two large ones already on your site plus 3 smaller ones - 2 of which happened sometime during the morning (they were not there when I left the car at 745). Also new slide in Bridger Gully. Plumes of snow blowing off the ridge / Saddle Peak"
Pinwheels of snow indicate the surface is wet and losing strength. These were observed at Bridger on 4/17/20, caused by a skier crossing above. Photo: A. Crawford
Obs (4/17/20): "Today while skiing at the Playground in the Bridgers my party triggered a wet slab on an ESE 33 degree slope at 7,700' (HS-ASu-R1-D1-I). No one was caught or injured. We decided to turn around as the sun was roasting the snow at 11:45 a.m., and picked a low angle slope to ski back to the trail. Skier 2 descended and popped out a slab about 10" thick and 50' wide, but the slide was slow moving at first and he was able to ski away. The slide gained momentum pretty quickly and ran powerfully about 250' down the slope."
From obs.(4/17/20): "Today while skiing at the Playground in the Bridgers my party triggered a wet slab on an ESE 33 degree slope at 7,700' (HS-ASu-R1-D1-I). No one was caught or injured. We decided to turn around as the sun was roasting the snow at 11:45 a.m., and picked a low angle slope to ski back to the trail. Skier 2 descended and popped out a slab about 10" thick and 50' wide, but the slide was slow moving at first and he was able to ski away. The slide gained momentum pretty quickly and ran powerfully about 250' down the slope." Photo: M. Talty
<p>This week a spring storm delivered 8-12” of snow (0.6 - 0.8” of <a href="https://www.mtavalanche.com/taxonomy/term/451">snow water equivalent</a> – SWE) to the mountains except near Cooke City and West Yellowstone which received 2-3” (0.3” SWE). During and following the storm skiers and riders triggered avalanches within the new snow, many ran fast and far. Look back through our <a href="https://www.mtavalanche.com/avalanche-activity"><strong>avalanche activity list</strong></a> to see a summary of these events. Warm temperatures and sunny skies today and intermittently through the weekend will rapidly increase the wet snow avalanche danger. When the snow under your feet starts getting wet or you see roller balls and pinwheels, stay off steep slopes, move to cooler aspects, or call it a day.</p>
<p>Avalanches breaking within the new snow and on weak layers buried 1-3’ deep are also possible this weekend. Wind will increase to 15-25 mph through the early part of the weekend creating new drifts of snow where skiers and riders could initiate a slide. If you see recent avalanche activity or cracks shooting out from your sled, board, or skis you found an area with unstable snow. Move on and find low angle terrain. Perform a quick extended column test to look for these instabilities if they don’t jump out at you. The storm moving into the area Saturday night does not look like it will bring significant snowfall. However, if the storm exceeds expectations, the avalanche danger will rise with new snow.</p>
<p>On Wednesday, there was an avalanche fatality in Colorado (<strong><a href="https://avalanche.state.co.us/caic/acc/acc_report.php?acc_id=757&ac… report</a></strong>). This was the third fatality in April (<strong><a href="https://avalanche.org/avalanche-accidents/">avalanche accident database</a></strong>). Be safe if you go into the mountains this weekend.</p>
<p><strong>Note if you are touring at Bridger Bowl</strong><strong>:</strong> Familiarity with the terrain from when the ski area is open influences our decision-making. Ski patrol has not done avalanche mitigation work in over a month and our “normal” routes may not be advisable. For example, the North Bowl Road crosses through the middle of serious avalanche terrain that is managed during the season. It is not a good route for your skin track as some skiers learned this week (<a href="https://www.mtavalanche.com/images/20/two-new-snow-avalanches-cross-nor…;).</p>
<p>See our forecast page and this <a href="https://www.mtavalanche.com/blog/transitions-spring-snow-avalanche-prob… general spring snowpack and travel advice.</p>
<p>Please continue to send us your observations. You can fill out an <a href="https://mtavalanche.us17.list-manage.com/track/click?u=6653a830e4819c9e…; target="_blank">observation form</a>, email us (<a href="mailto:mtavalanche@gmail.com" target="_blank">mtavalanche@gmail.com</a>), leave a VM at 406-587-6984, or Instagram (#gnfacobs). We greatly appreciate your support.</p>
Give Big Gallatin Valley is April 30th - May 1st. The Friends of the Avalanche Center are participating again this year and want to thank all of you for your support.
