Lawinenlagebericht

Banner Summit

Sawtooth Avalanche Center
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Lawinengefahr

Sun
Hochgebirge
4 · Gross
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Kernpunkte

A large multi-day storm has created very dangerous avalanche conditions. Destructive natural and human-triggered avalanches are very likely. Stay off of and out from beneath slopes steeper than 30 degrees. Slides may break wider, be triggered remotely and run faster + further than expected today.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Very Likely
    Größe
    1.5–2.5

    You are very likely to trigger 1-3 foot thick slabs in wind-loaded terrain today. The size and reactivity of avalanches will increase as you climb into windier terrain above 8000 ft, especially on slopes that face N-NE-E-SE-S.

    Look for wind slabs near or below ridgelines, along mid-slope ribs, and on aprons beneath chutes. Cracks shooting out in front of your sled or boards mean you've found a sensitive slab. Pillowy and lens-shaped drifts of snow are obvious features of recent wind loading and indicators of building slabs. You can manage your exposure to this problem by identifying and avoiding wind-loaded slopes, including the gentler terrain below or connected to large starting zones.

    Avalanches could break wider than you expect, be very easy to trigger, and run faster + further where storm snow buried slick crusts, facets, crusts + facets, or surface hoar. Avalanches involving new storm snow will be dangerous on their own, but they also increase the chance of very large avalanches breaking on persistent weak layers buried deeper in the snowpack (Problem #2 below).

    (12/18/2025)

    We found natural avalanches on the NE slope of the summit of Copper Mountain (8900 ft). These appeared to have released yesterday and looked to be thin wind-slabs.

    Photo: Sawtooth Avalanche Center

  • Persistent Slabs

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

    A couple of unstable weak layers exist below 2-4 ft (50-130cm) of snow. Intense loading (snow + wind) during the multi-day storm is actively testing the limited strength of those buried layers. Avalanches involving these layers may be harder to trigger today, but will probably be very large and likely unsurvivable.

    We have continued to see cracking, collapsing, unstable test results, and natural avalanches related to the multiple crust/facet combos that are now tucked under a heap of new snow. It is going to take a whole lot more time for the buried weak layers to adjust to the additional snow load. The most suspect locations for these crust/facet combinations are W-NW-N-NE-E-SE facing slopes at middle and upper elevations (near and above ~8000' in this zone).

    Avoiding travelling on or below steep slopes where you suspect this weak layer to exist is your best bet to keep out of trouble today.

Avalanche Discussion

The clouds may clear today, but unfortunately the avalanche danger hasn't. We've now made it through two rounds of this whopper of a multi-day storm and are lined up for a little breather today before another juicy pulse of moisture rolls in on Sunday. Don't let the relatively more pleasant weather lull you into a false sense of security today - it is still very likely to trigger a large and potentially deadly avalanche.

Yesterday, two members of our forecast team were caught off guard when they triggered, were caught, and carried in a small wind slab avalanche above the Baker Lake trailhead (click here for more information).  Fortunately, everyone is alright and the piece of terrain they were travelling on was relatively small. What's tricky about their avalanche is that it was triggered only a few steps off of a wind-scoured ridgeline with sagebrush sticking out. These consequential micro-terrain features can be challenging to read, especially during and after a big dump of snow and honking winds. The take-home we discussed while debriefing this near-miss was to build in bigger margins during these times of high danger.

There's uncertainty during ongoing storms, but here's what we do know:

  • Below the recent rain-line (~9000 ft), we're mostly concerned with storm-snow problems above a stout crust
  • Above the recent rain-line, we're more concerned with larger, deeper avalanches failing on buried weak snow

If you choose to go out in the mountains today, please play it safe and let us know what you see.

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