21-22 | Gallatin National Forest Avalanche Center

We toured into the Southern Gallatin Range near Specimen Creek and found a very thin, very weak snowpack that is stable for now because it is missing a key ingredient for avalanches, a slab. For now, we are watching out for areas of isolated instability in areas where there is more cohesive snow sitting on top of weak layers. Photo: GNFAC

No Region, 2022-02-27

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GNFAC Avalanche Forecast for Sun Feb 27, 2022

Snowpack and Avalanche Discussion

Yesterday in the northern Bridgers three separate groups of skiers triggered slabs of wind-drifted snow that broke 8-18" deep and some were hundreds of feet wide. One person was caught, but unharmed (<a href="https://www.mtavalanche.com/node/25997">details and photos</a>), and a handful of other slides were remote triggered and nobody was caught (<a href="https://www.mtavalanche.com/node/25992">details and photos</a>, <a href="https://www.mtavalanche.com/node/25989">details and photos</a>).

On Friday and yesterday, westerly winds increased and drifted recent snow into hard slabs over the sugary, weak snow that formed during previous cold, dry weather. Yesterday’s avalanches are a clear sign that an unstable snowpack exists on wind-loaded slopes. The weak layers that were buried by recently formed drifts are “persistent” which means they are slow to gain strength and can remain unstable for many days or weeks. This weak snow exists from Big Sky to West Yellowstone, and although the bulk of yesterday’s activity was centered on the Bridger Range, recent small slides near Big Sky, Mt. Blackmore and in Teppe Basin are signs that unstable snow can be found, and avalanches are possible where wind has drifted snow into slabs above the weak snow (<a href="https://www.mtavalanche.com/node/25999">Mt. Blackmore photo</a>, <a href="https://www.mtavalanche.com/images/22/fresh-wind-slab-near-summit-blaze… Mtn. photo</a>, <a href="https://www.mtavalanche.com/images/22/snowmobile-triggered-slides-teepe… Basin photo</a>).

Today avalanches are possible to trigger on wind-loaded slopes. Before riding on steep slopes, carefully assess the potential for wind-loading and buried weak layers. On slopes without recent drifts of snow, avalanches are unlikely. Avalanche danger is MODERATE on wind-loaded slopes and LOW on non-windloaded slopes.

A weak layer of snow buried 2 feet deep makes it possible for a person to trigger a large avalanche. Avalanches breaking on this weak layer become less likely to trigger each day without snow, but the consequences of being caught are potentially deadly. Examples of the type of avalanches you could trigger are two snowmobiler triggered avalanches last weekend, one of which was fatal (<a href="https://www.youtube.com/watch?v=qC7geA4kgyg&list=PLXu5151nmAvT1nrM2… Mountain fatality video</a>). Two days ago I found unstable test results adjacent to one of these slides (<a href="https://www.youtube.com/watch?v=LHkbEAf1rlM&list=PLXu5151nmAvT1nrM2…. Abundance video</a>, <a href="https://www.mtavalanche.com/node/25941">details…;) which shows conditions still exist to trigger a large avalanche. Before you travel on steep slopes, carefully assess the snowpack for potential instabilities and consider the consequences of being caught in a slide. Large avalanches are possible and the avalanche danger is MODERATE.

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">websi…;, email (<a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</str…;), phone (406-587-6984), or Instagram (#gnfacobs).