Avalanche forecast

Tetons

Bridger-Teton Avalanche Center
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Avalanche danger

Sat
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 2 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

The avalanche danger will start at Moderate and rise to Considerable throughout the day, as new snow and wind make triggering a soft slab avalanche likely in steep, wind-loaded terrain at the upper elevations. To reduce your risk, steer clear of obvious drifts and slopes where the wind has stiffened the snow surface.  Careful snowpack evaluation is recommended around avalanche terrain today, as the possibility of triggering a larger avalanche 2.5-4 feet deep remains in isolated terrain above 8,500'.

The NWS has issued a Winter Storm Warning that is in effect until Friday, 11:00 PM.

 

Avalanche problems

  • Wind Slabs

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

    Overnight, 4 inches of snow fell in the Tetons with winds gusting 45-55 mph. Snow totals today are anywhere from 6-12 inches, with the highest rates this morning. Uncertainty exists in the weather forecast; if snowfall amounts trend towards the higher end, expect the hazard to rise. Sensitive wind slabs will grow in size and distribution as you move higher in elevation.  The best way to avoid this problem is to avoid steep slopes or consequential terrain where you find indications of recent wind loading. Watch for snow that is denser than snow found on wind-sheltered slopes and tell-tale clues such as surface texture and a pillowed, drifted appearance. 

    (2/4/2025)

    Windy Ridge lives up to its namesake, with textured, winded snow. Later today as new snow stacks up, avoid areas where you encounter dense drifts of new snow. 

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2.5

    Since 1/31, several feet of snow has fallen on a weak snow interface. This interface is now buried beneath a slab of snow that is 2.5-4 feet thick and, if triggered, can propagate across large distances. The activity on this layer matches how a warmer maritime storm falling on a persistent grain type may trend: a fairly rapid spike in activity followed by a faster dip towards becoming less reactive. The distribution of much of this snow is also still uncertain, but human-triggered avalanche activity has most notably been observed on N-NE-E aspects. With the nature of the slab of snow above this weak layer, as well as the depth of burial, apparent signs of instability, such as cracking, collapsing, or recent natural avalanche activity, are not likely to present themselves before triggering a large avalanche. It is worth digging and looking for in the top 3 feet of the snowpack

    (2/3/2025)

    A large skier-triggered avalanche on a NE-facing slope at 9,400' south of JHMR. It likely failed within the new snow on a density break and was thickened by wind loading. 7 skiers were caught and carried. All members of the party survived the incident.

Avalanche Discussion

It's time to take stock and make sense of the complex new layer cake existing in the top meter of the snowpack. Today, primarily, be on the lookout for new snow instabilities. Here is some food for thought as we look forward to more "boots on the ground" observations in the coming days. Let's consider what we do and don't know.

Observations so far (knowns):

  • Numerous large human-triggered avalanches occurred last week on aspects ranging N-NE-E—not surprising, given the massive snowfall, intense precip rates, and strong winds. 
  • Not much natural avalanche activity has been observed on the 1/31 weak layer, but lack of evidence does not imply evidence of lack.

Observations needed (unknowns):

  • Will the crust/facet layer buried 1/31 on steep, sunny slopes be a thing or not? Sometimes, trends seem to appear simply due to observation bias. 
  • How will 1/31 age on all aspects?
  • How will new snow bond to the graupel/mixed bag interface today?

Until we get a better handle on our brave new world and the "knowns" list is longer than the "unknowns," I'll be embracing a wait-and-see attitude.

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