5 ft deep explosive triggered slide at Big Sky Resort
Big Sky Ski Patrol used explosives to trigger an avalanche that broke 5 ft deep on weak layers near the ground.
Big Sky Ski Patrol used explosives to trigger an avalanche that broke 5 ft deep on weak layers near the ground.
<p>A big dump of new snow with strong winds means that human triggered avalanches are likely today. The Fisher Creek SNOTEL site is showing 18” (1.8” <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/null/?cid=nrcseprd1314… Water Equivalent</u></a>) of snow over the last 48 hours and we’ve received reports of substantially more snow at higher elevations. You could trigger an avalanche within the new snow (especially in wind drifts), on a layer of weak snow in the middle of the snowpack, or on weak snow at the ground. Don’t get caught up in the details - with so much new snow, wherever a slide breaks it will be large and dangerous. Keep it simple. Stay off of and out from under any slope steeper than 30 degrees. Human triggered avalanches are likely and the avalanche danger is rated CONSIDERABLE. </p>
<p>With a foot of fresh snow (1.1” SWE) and strong southwest winds avalanches will break easily today on wind loaded slopes. Expect to trigger avalanches within the new snow and they could also break on the weak layers near the ground (<a href="https://youtu.be/7EEn6f8-4fA"><strong><u>video</u></strong></a>). Look out for and avoid steep wind-loaded slopes. If you aren’t confident in identifying wind-loaded slopes, just avoid all steep slopes. The avalanche danger is CONSIDERABLE on wind-loaded slopes. On slopes without wind-drifted snow avalanches are possible and the avalanche danger is MODERATE.</p>
<p>Seven inches of new snow (0.7” SWE) isn’t enough to spike the danger, but does mean it’s possible to trigger dangerous avalanches on steep slopes that are either wind drifted or have weak snow at the base of the snowpack (<a href="https://youtu.be/2rjpm0iLm_I"><strong><u>Tepee Basin video</u></strong></a>). Look out for particularly deep wind-drifts or slopes where a small slide could pile up deeper in a gully or push you into obstacles. Human triggered avalanches are possible and the avalanche danger is MODERATE.</p>
<p>Fresh wind drifts are the primary concern near Bozeman and Big Sky. Yesterday, Alex and Doug triggered a small wind slab while looking at the snowpack on Saddle Peak (<a href="https://www.youtube.com/watch?v=_MhpDHnH8So"><strong><u>video</u></stro…;). With new snow and strong to extreme winds overnight, expect to find fresh reactive wind drifts on many slopes. While the lower snowpack is generally stable (<a href="https://youtu.be/cf-qqv2Ssjw"><strong><u>Buck Ridge video</u></strong></a>, <a href="https://youtu.be/ePMCJs3qAs0"><strong><u>Beehive video</u></strong></a>), yesterday, Big Sky Ski Patrol used explosives to trigger a 5 ft deep avalanche that broke on weak snow near the ground. Let this be a wake up call and reminder to not discount the basal weak layers that exist across our advisory area. The avalanche danger is rated MODERATE on wind-loaded slopes and LOW on all others.</p>
<p>If you get out, please send us your observations no matter how brief. You can submit them via our <a href="https://www.mtavalanche.com/node/add/snow_observation"><strong><u>websi…;, email (<a href="mailto:mtavalanche@gmail.com"><strong><u>mtavalanche@gmail.com</u></str…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>
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Get your avalanche brain ready for the season at one of the many classes listed on our education calendar, and list of upcoming events below.
Every Saturday near Cooke City, 10 a.m.-3 p.m. FREE snowpack update and transceiver/rescue training. Stop by for 20 minutes or more at the Round Lake Warming Hut.
We were able to intentionally trigger this 6-8" deep wind slab on Saddle Peak on December 23, 2021, E aspect at 9,000'. It showed us that recently formed wind slabs were still reactive. This hard slab formed over low density new snow which made it unstable. While not large, these slides will easily push you down and can be harmful if they push you into hazardous obstacles or terrain traps. - GNFAC
We intentionally triggered this 6-8" deep wind slab on Saddle Peak on December 23, 2021, E aspect at 9,000'. It showed us that recently formed wind slabs were still reactive. This hard slab formed over low density new snow which made it unstable. While not large, these slides will easily push you down and can be harmful if they push you into hazardous obstacles or terrain traps. Photo: GNFAC
This is second hand from a reliable source in the Philipsburg ski/snowmobile community. Backcountry skiers on a north aspect near the Powell mine, North Flint Range, were digging a snow pit when the slope avalanched with the crown through their snow pit. Slab avalanche was estimated at 16 inches and slope was wind loaded. Avalanche ran 6-800 feet. Skiers stayed in the snow pit and no one was caught.
On December 23, 2021 we went out to Saddle Peak and dug three snowpits. We found a 2-3 foot deep, generally stable snowpack with a lack of unstable buried weak layers. Photo: GNFAC
Obs are from Wednesday 12-22: Toured in afternoon from normal parking to ridge above low angle runs. OVC sky, Prec. S-1, cool temps -6 at TH, -10 at ridge. HS 35-40 at bottom, 70-80cm @8,260 ft, 110-120cm at ridge where wind protected on shady asps. HS is quite variable this season between the meltdown in early Dec. and abundant wind redistribution. Found as little as 40cm in wind affected areas even at 8800'. Test profile below ridge top in a protected zone, asp 70 deg, 25 deg slope, HS 115. Poor snowpack structure, 1F slab over a decomposed crust at 40cm, with layer of concern of 20cm of 4F- 2mm FC below. CTH21(Q1)x2 at 38cm. Layer will propagate a fracture, ECTP22@38 ish. No real news there, this is much the same as the obs from Buck and Tepee. No Whumpfing observed, and I did break substantial different trail in the meadows. Isolated Cracking around skiis in shallow areas. Travel conditions are good up high, marginal at low elevs.