Avalanche forecast

East Slopes South

Northwest Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 2 years ago.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

Highlights

You can trigger avalanches in wind-drifted terrain, but triggering a larger slab will become increasingly more possible as new snow stacks up. Adjust your plans accordingly and simplify your terrain selection once you notice 6 or more inches of new snow. Shooting cracks, whumphing collapses, and fresh wind deposits are all great reasons to dial it back. 

Avalanche problems

  • Wind Slabs

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

    A new generation of wind slabs will build in size and distribution as the day progresses. Initially these wind slabs will start small, but expect slab size and sensitivity to increase as precipitation rates increase. 

    You’ll typically find these unstable slabs beneath exposed ridgelines, below cornices, and on mid-slope convexities in exposed terrain. It won’t be the day to search these things out though. You’ll want to use avoidance techniques, like paying attention to blowing snow and surface textures. Ripples and dunes at the snow surfaces are clues of recent wind loading. Shooting cracks, whumphing collapses, and the possibility of triggering larger avalanches are good reasons to skirt around wind loaded terrain.

    (12/13/2024)

    Blowing snow and firm pillow-like drifts are great clues to anticipate wind load slopes. 

    Photo: ONP Rangers

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    Moderate new snow loads will continue to add weight to weak layers 1-3 ft below the surface. You can trigger avalanches that break roughly 1ft on more recent weak layers that were buried earlier week or more concerning, on weak snow from our January drought. The most likely place to get unlucky will be in wind loaded terrain, but don’t write off more sheltered terrain, especially if you notice more than 6 inches of new snowfall. 

    You may or not receive any warning signs like cracking or collapsing before triggering a large persistent slab. Persistent Slabs can release in surprising ways, propagate widely, and release from a distance away. You can't assume that tracks on a slope means it is stable.  These persistent slabs surprise people every year. You can reduce your exposure by avoiding steep, open slopes that face NW-N-NE, especially if they appear wind stiffened.

Avalanche Discussion

This may be a pretty good storm for the eastern cascades. The start of the day may not feel that dangerous outside of wind loaded terrain, but expect an increase in danger as precipitation rates increase during the day. If you find more than 6-8 inches of new snowfall, start thinking about storm slab instabilities in more sheltered terrain. 

Any new precipitation amounts can increase the chance of triggering bigger and more scary persistent slabs. Its important to keep our weak snowpack in mind and not play your normal playbook as new snow starts accumulating. Adjust your practices to simply avoid steep slopes that harbor a weak snowpack. 

Observations are key in producing a more accurate avalanche forecast. Let us know what you see by submitting an observation. 

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