Bollettino valanghe

East Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

Wind-transported snow can be found in exposed, downwind slopes. Blowing snow, shooting cracks, and recent slab avalanches are signs that this snow is unstable. Stick to slopes less than 35 degrees where you find any of these signs.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    Another storm system rolls through starting on Thursday night accompanied by winds up to 30 mph. This will build fresh slabs on lee slopes at middle and upper elevations. Fresh slab formation can overload older wind slabs and produce a bigger and even more consequential avalanche. There may be a layer of buried surface hoar within the snowpack and recently developed slabs will have formed over it.

    Blowing snow will be your first indicator that slopes are being loaded. Rippled, uneven snow surfaces also indicate wind transport, but this may not be obvious if obscured by new snow. If you encounter hard snow surfaces, rapid changes in snow depth, and cornices, presume that deeper slabs can be found just below ridgelines and in cross-loaded gullies. Surface hoar often appears as a thin grey line in a snowpit wall; you can dig a quick hand pit to check for it. Cracks shooting from your skis or sled indicate that you have found an unstable slab. 

    (12/31/2024)

    Cornice fall triggered a small 1ft deep wind slab avalanche in the East South zone recently.

    Photo: Payton Schiff

Avalanche Discussion

The East South zone should see up to 0.75" of water in the warm front impacting the zone. The expected moderate wind speeds are a bit more noteworthy, however. Typically, moderate wind is the prime transport speed for building wind slabs. So we expect new slabs to form, but some uncertainty lies with how well they will bond to themselves and layers below given the overall warmth of the system. Additionally, this storm will be more easterly and will blow snow onto slopes that have typically not been heavily loaded up until this point. If you have been getting out and finding wind loading on only north and east-facing slopes, don't be surprised if you encounter instability on a more west-facing slope.

If you see cracking or recent slab avalanches in lower elevation, wind-sheltered terrain, you have found some storm slab instability. There is a robust crust at lower elevations that could act as a slick sliding surface if enough snow falls on top and overloads the strength of the slab. Mark that as a sign to avoid steep slopes at all elevations. 

We have little information about the lingering persistence and distribution of buried surface hoar. It was previously observed on the surface on all aspects at middle and upper elevations. Surface hoar is a notoriously weak snow grain once buried, and my hackles are always raised if I know it may be lurking in the snowpack. Until we have more information regarding its presence, it would be a good idea to dig around and look for it before stepping into avalanche terrain.

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