Lawinenlagebericht

Snake River Range

Bridger-Teton Avalanche Center
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Lawinengefahr

Fri
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
1 · Gering
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Kernpunkte

New snow and wind have created dangerous avalanche conditions. Human triggered avalanches are likely and natural avalanches are possible in steep, wind loaded terrain at middle and upper elevations. Smaller avalanches have the potential to break into deeper layers and cause large and destructive avalanches. Wet snow avalanches are possible at middle elevations. Be conservative around and under steep slopes today. Watch for shooting cracks, collapsing in new snow, and wet snow surfaces.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2

    Up to 7 inches of snow and moderate southerly winds have formed soft slabs up to 2 feet thick on leeward aspects. You will likely trigger small wind slab avalanches on steep, wind loaded slopes at upper elevations. Winds in the last 24 hours veered from southeast to southwest. Expect wind slab distribution to extend further onto northwest aspects than with recent storms. Wind slabs may exist down to 8500’ by the end of the day as temperatures cool. Terrain below ridelines and around steep rocky slopes warrants caution. Look for signs of wind loading, including drifting snow, shooting cracks, and collapsing - all good indicators of unstable snow.

    (12/20/2025)

    Watch for pillows, shooting cracks and collapsing in new snow.

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    1.5–3

    The 12/10 rain crust sits 2-4  feet below hard slabs. While the slab above this layer has gained strength, new snow, rain, and wind continue to add stress. Several large avalanches involving this layer occurred in the last week, but activity involving this crust has slowed. The last large avalanche involving this layer was three days ago. It is becoming unlikely that you will impact this layer, but the potential remains for smaller avalanches to step down to this layer. This crust could act as a very large and well-connected bed surface, and any avalanche at this depth could propagate far and fast and be very large and destructive.

    (12/20/2025)

    Large natural avalanche that failed on the 12/10 crust.

    North Aspect, 10,000'

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–1.5

    With rain up to 9000 feet overnight, expect to find saturated snow surfaces. Wet loose avalanches are possible in very steep terrain and may entrain more snow than expected.  Even small wet snow avalanches can easily knock you over. If you see rollerballs originating from your skis, stick to gentler slopes and watch out for narrow gullies and terrain traps.

Avalanche Discussion

On the first day of Christmas, you get a persistent slab avalanche problem, not a partridge in a pear tree. A few thoughts regarding this problem…

  • Current snowpack conditions don’t always fit nicely into the avalanche problem drop-down menu options that I scroll through in the morning. This is one of those cases for the reasons stated above. Persistent slab comes closest to fitting the bill and we will track it as such. I suspect this layer will continue to be buried and become unreactive sooner rather than later.
  • The 12/10 crust is not a persistent weak layer, per se. There are some facets surrounding this crust in places, as well as some preserved graupel, but one could argue it does not meet the criteria of a persistent grain. For this reason, it could be (and hopefully will be) a short-lived problem.
  • Although lacking the persistent grain, it has behaved very much like a persistent slab problem with avalanches involving this layer in the last week. These avalanches have propagated far and wide, due in large part to the well-connected nature of this layer. The character of these avalanches suggests a persistent slab problem. The amount of time we have been tracking it (9 days) also points to a persistent slab problem. As a very general rule of thumb, wind slabs transition to persistent slabs after 3 days if they are still a problem AND they are sitting on a persistent grain. Only partly true in this case.
  • ECT’s targeting this layer at middle and upper elevations in the Tetons yesterday did not produce propagation. These tests were on east (9k’) and northeast (9.5k) aspects. The unfortunate realty however, is that stability tests don’t always work well with crusts, and can lead to some uncertainty.
  • By assigning the 12/10 layer its own problem, we are able to more accurately communicate the size, distribution, and likelihood of the current problem set using the graphics in the forecast and not rely on long-winded discussion - and if you’ve read this far, it’s clear I still can’t help myself.

Maybe by the seventh day of Christmas, we can hope for just seven swans a swimming and a straightforward snowpack.

 

Merry Christmas!

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