Avalanche forecast

Olympics

Northwest Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
1 · Low
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Highlights

Winds will form slabs on top of two potentially weak and reactive interfaces on Sunday. Any slab you trigger could step down, creating a large and destructive avalanche. It's a good day to dial back your terrain selection and choose supported, smaller terrain features rather than steep, open, wind-loaded slopes.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    New snow and wind loading will put our Persistent Weak Layer (PWL) to the test. It has been buried 1-2 feet, but may be more deeply buried in wind-loaded terrain by Sunday.  We don't expect you will trigger this weak layer without a slab and that slab arrives in the form of denser snow and wind loading. Carefully evaluate small test slopes, looking for wind slabs or denser snow that may prove problematic on a steep slope. Uncertainty surrounding the likelihood of triggering such an avalanche would have us traveling far more conservatively than normal. Keep a buffer between yourself and open slopes steeper than 35 degrees, particularly those that have actively or recently wind-loaded on the shaded half of the compass. Whumpfs or collapses confirm the problem and warrant avoidance of all open slopes steeper than 30 degrees. A cornice fall or wind slab could step down, triggering a deeper, more widespread slide. 

    (2/2/2025)

    A widely propagating slab avalanche on a North aspect in the Maggie's area.  A shooting crack on the same slope shot out a whopping 40'.  While this avalanche occurred during a storm cycle, it likely failed on the persistent weak layer we're still tracking. 

    Photo: Anthony Anglikowski

  • Wind Slabs

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

    With another 3-6" of snow expected above 4000 ft through Sunday, expect slabs to become widespread and potentially large. Unfortunately, we're dealing with an overlapping problem set. Wind slabs may rest above a recently buried weaker 2/14 interface that may hold patchy surface hoar.  Any slab failure also increases the likelihood that a slab will step down to the PWL we've been dealing with since the end of January. Keep a wider margin of space between yourself and actively or recently wind-loading steep slopes, particularly on shaded or E aspects.

     

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

    Photo: ONP Rangers

Avalanche Discussion

Around an inch of new snow was transporting moderate amounts of snow by Saturday afternoon, creating the potential for more widespread small avalanches by the end of the day. Avalanche conditions will deteriorate further Saturday night and Sunday with more snow and wind loading. 

Given a complex upper snowpack, limited recent observations, and a lot of uncertainty, the best way to manage a challenging and poor structure in the upper snowpack is to limit your terrain selection and stay disciplined. Treed slopes can be a good option or limit the scale of the features you choose to engage with.

Snow conditions remain excellent in shaded wind-sheltered terrain, but likely formed reactive shallow slabs near ridgelines on Saturday.   Despite the cold weather earlier in the week, sunny weather had formed a sun crust on southerly aspects, making for less than pleasant travel conditions.  Surface snow had weakened amidst the cold weather on shaded aspects, with surface hoar remaining anywhere the sun didn't reach; it may have been buried in some areas by a skiff of snow Friday and will be something to watch moving forward. The more concerning layer of weak snow is the PWL we are tracking:  Facets are sandwiched between a series of crusts (1/10 and 1/29) 1-2' below the snow surface on shaded aspects.  In some areas, there may be a very thin layer of facets above the upper crust.  This crust/facet complex is the likely culprit of a series of widely propagating, human-triggered avalanches during the 2/1 - 2/2 weekend and a series of whumpfs last Sun and Tue.   We are going to keep warning about this interface as new snow gradually accumulates and temperatures warm through the holiday weekend. At lower elevations, we don't think there's yet enough snow loading to create a problem.

Share your observations with the community and NWAC. Even if you didn't see an avalanche or a snowpack test, your information is incredibly valuable.  Every afternoon, 4-5 NWAC forecasters from around the region meet to discuss the latest snowpack and avalanche observations, and weather forecast to create the next day's avalanche forecast.  We look at information from the public, other snow professionals, and weather station data to round out our picture.  Share early and often!

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