Avalanche forecast

Snake River Range

Bridger-Teton Avalanche Center
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Avalanche danger

Fri
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Very dangerous avalanche conditions exist with rapid loading of new snow creating reactive wind slabs and stressing weak layers near the base of the snowpack. Caution is advised as careful route finding is necessary to avoid slopes over 30° where these avalanche problems could be found. The best way to manage these problems is to avoid steep, rocky, and wind affected slopes in the middle and upper elevations where avalanches will be the most consequential. 

 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1–2

    Large amounts of snow combined with sustained west/southwest wind around 20 mph in the last 24 hours has formed fresh slabs up to 2’ deep. Slab depths will be larger and more consequential in the upper elevations that contain more open and wind exposed slopes. Look for obvious signs of instability such as large drifts, cracking, or hollow sounding snow. Avoid leeward and cross loaded terrain such as off ridgelines where wind slabs are most likely. 

    Storm slabs: Rapid loading of up to 12” of new snow will also make triggering avalanches in terrain sheltered from the wind across all elevations possible. Test the new snow to see how it is bonding before committing to avalanche terrain over 30°.

    (12/28/2024)

    Look for signs of unstable new snow such as cracking surfaces seen here. 

    Photo: John Fitzgerald

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–3

    Weak layers of faceted snow buried 2-4’ deep have been stressed with rapid loading of new snow. Areas that harbor a shallower snowpack around 2-3’ is where it is possible to trigger a very large avalanche, as the overlying slab is thinner and easier to impact the weak layers. One of these avalanches was remotely triggered three days ago on a slope with a shallow snowpack in Indian Creek resulting in two full burials. Watch out for slopes over 35° with similar characteristics that are rocky, shallow, and wind affected on W-N-E aspects above 7500’. Persistent slabs can behave in unpredictable ways. Multiple tracks on a slopes do not indicate stability and avalanches could be triggered remotely from gentle terrain above, below, or to the side of steep slopes. 

    (12/31/2024)

    Large remotely triggered avalanche that failed on persistent weak layers. The avalanche propagetd out of view to the left and right.

     

Avalanche Discussion

Around a foot of new snow has fallen in the last 24 hours with an additional 5-8” forecasted today from the lower to upper elevations. Lower elevations received 12" at 5600' (Snake River Canyon weather station) in the last 24 hours. This has created red flag avalanche conditions where triggering an avalanche will be very likely in upper elevation wind loaded terrain. Triggering a large wind slab could step down to persistent weak layers. In addition, over 1” of snow water equivalent will add stress to these weak layers buried near the base of the snowpack. There is a large spatial variability in how deep these weak layers are buried. Slopes with a deeper snowpack will be harder to trigger these weak layers. The caveat is that predicting where the snowpack is deep or shallow can be very difficult. Obvious signs of instability for persistent slab avalanches such as collapsing may not occur. For this reason, the best way to manage the persistent slab problem is to seek safer terrain below 30°. Let the snowpack adjust to the rapid loading and stick to more conservative terrain choices for the time being.

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