Avalanche forecast

Tetons

Bridger-Teton Avalanche Center
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Avalanche danger

Sun
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

It will be possible to trigger an avalanche 2-4 feet deep in steep wind loaded upper elevation terrain. Careful assessment of the snowpack will be critical in avoiding avalanches. Sticking to lower angle slopes while the most recent load has time to adjust will be essential today.

Avalanche problems

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    Weak snow that formed during a prolonged dry spell in December remains a lingering threat. Reactivity on this layer is approaching a dormant phase but is not there yet. Waking up this beast remains possible and is more likely to occur as the result of a large avalanche involving the newer snow stepping down to this interface.  Avalanches in this category fall into the 3-5 foot depth range and would be unsurvivable if one were to get caught, carried and buried.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Snowfall over the last week has created slabs in the 2-4 foot range. These slabs are sitting on weak snow in the upper elevations on all but south aspects. Instability peaked on this interface 2-3 days ago, when a natural avalanche cycle occurred. One large remote triggered avalanche was also reported during this time period as well. Reported activity occurred mainly on the north half of the compass and initiated in steep wind loaded starting zones. This terrain harbors the most suspect snow today. Approach any terrain in the upper elevations with suspicion. Be on the lookout for obvious signs of instability such as shooting cracks and whompfing. When these signs are present it is time to back off and choose simpler terrain. Tracks on a slope are not a guarantee that the snow is stable.  Make your own assessment of a particular slope before committing to any terrain capable of producing an avalanche.

    Large remotely triggered avalanche on Four Pines just outside the JHMR boundary highlighting the poor new to old snow interface. 

    Photo: Josh Pope

Avalanche Discussion

We have transitioned to what we were calling a “storm slab” yesterday to a “persistent slab” today. A significant warm and dry period occurred between Jan 29 and Feb 2. This resulted in melting of snow surfaces and crust formation on all aspects in the mid and low elevations as well as upper elevation terrain on the south half of the compass. Upper elevation terrain on the north half of the compass was left with facets, some surface hoar and generally weak snow. Snowfall that began on Feb 2nd and tapered off yesterday built slabs ranging from 2-4 feet thick. Snow water equivalent of this slab is 2.5-4”. This is a significant load over a short period of time. Bonding at the Feb 2 interface ranges from good to poor.  As a result there was a natural avalanche cycle that likely peaked 3 days ago. While observations have been limited by low visibility, the information that has been gathered points to a fairly widespread avalanche cycle in the Tetons.

Deeper instability remains on the radar as the Feb 2nd interface takes time to adjust. The last known activity on this layer occurred south of Teton Pass on Feb 3rd. It is possible that some of the more recent avalanche activity stepped down to this interface, but there is uncertainty around this fact. While reactivity is trending towards dormancy on this interface, there is enough uncertainty to warrant a conservative approach. Low likelihood/high consequence situations such as this require patience and vigilance in how we travel through avalanche terrain.

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