Boletín de aludes

Northern Wallowas

Wallowa Avalanche Center
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Peligro de aludes

Fri
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
2 · Moderado
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Desactualizado: este boletín caducó 2 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

New snow and wind-blown snow from yesterday could remain sensitive to the weight of a rider today.   While the chances of triggering a deeper persistent slab avalanche have decreased, continue to use caution, especially in areas where the snowpack is thinner and harbors wind-blown snow sitting above the weak January facets.  

This forecast is sponsored by Wallowa County Search and Rescue.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    Dense storm snow from yesterday combined with light to moderate winds has packed the new snow into cohesive slabs in exposed terrain.  In many places, this new and wind-blown snow sits above less dense snow and/or older wind-packed layers that could make an excellent bed surface.  In areas where you find weak January facets 2-3 feet from the surface, a new snow avalanche has the potential to step down into this older snow creating a larger avalanche.  

    You are most likely to find windslabs along exposed ridgelines, underneath cornices or on exposed mid-slope features.  Look for signs such as rippled snow texture, dune-like features, up-wind locations being blown clean of new snow.  If you experience shooting cracks or whumphing of the snowpack, you are getting a free clue to dial back your terrain choices.  

    (2/5/2025) Photo: Caleb Merrill

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely
    Tamaño
    2–3

    While becoming increasingly less likely, it is still not out of the question to trigger a deep and unsurvivable avalanche on the weak January facets that sit 3-4' below the snow surface.  Observers are finding mixed results in their snowpack tests, and in many places, the snowpack structure is missing a firmer bed surface layer below these facets for an avalanche to slide. 

    While the danger level has dropped to moderate due to the likelihood of triggering these avalanches, don't be mistaken- the consequences of triggering an avalanche on this weak layer remains significant.  Treat this problem as a "low-likelihood/high-consequence" possibility and evaluate consequential terrain on a slope-scale level.  

    The most likely place to trigger an avalanche on these weak January facets will be in areas that hold a shallower snowpack with a cohesive slab of snow above them.  In some protected areas in the region, Surface Hoar has been observed sitting above the January Facets.   This set up could be particularly sensitive. 

    Persistent slabs often resist showing their hand, and may or may not offer obvious signs of instability such as shooting cracks or collapsing of the snowpack.  Continue to use careful terrain and group management techniques: Only expose one person to a slope at a time, keep eyes on, and always regroup well clear of avalanche runouts.  

    (2/10/2025)

    Crown from a natural avalanche

    Photo: Victor McNeil

Avalanche Discussion

What Happened? 

Yesterday brought consistent snow to the Western and Southern Wallowas and ultimately dropped 6-8" of snow in these zones, but just a trace of new snow was reported in the Northern Wallowas.  Many of our wind stations are rimed up and not reporting accurately, but it seems like winds were variable, with gusts in the 30's reported at Mt. Howard and slightly less in the Western and Southern Wallowas. 

What's does it look like....and what is the likelihood? 

It is possible to trigger a new snow avalanche in storm snow or wind-blown snow that would be 6-18" deep.    The weight of a new snow avalanche has the potential to step down into older weaker snow buried 2-4' in the snowpack. 

To re-emphasize the Persistent Slab problem, just because it is unlikely, doesn't mean it's impossible.  The way I see it, it's the old "needle in the haystack" scenario.  Just because you see yellow on the danger scale, doesn't mean it's good to go.  If you get it wrong and are mid-slope when a persistent slab avalanche releases, the outcome will not look good. 

As the sun pops out and temperatures increase, start thinking about wet loose avalanches.   If you are seeing rollerballs/pinwheels or sinking up to your ankles in wet sloppy snow, retreat to shadier aspects and avoid riding above terrain traps. Throughout the weekend, if we get the rain on snow that is forecasted, this problem will become much more real.  

What to do about it? 

The new snow and wind-blown snow could remain sensitive today.  Hand shears, as well as riding over or ski cutting small (inconsequential) test slopes will give you a lot of information today as to how the new snow is bonding to the old surfaces.   

You will find many long-time professionals in the area still sticking to slopes 30 degrees or less to manage the Persistent Slab problem.  Continue to dig down and investigate the structure of the snowpack.  If you find hard over soft with a firm sliding (bed) surface below, you have all the right ingredients for a slab avalanche.  

Use terrain to your advantage and manage your group well. 

You can't get caught up in an avalanche if you aren't in avalanche terrain.  Evaluate the terrain carefully, and if you decide to engage in avalanche terrain, manage your communication and your partners well.  Only expose one person at a time to avalanche-prone slopes, keep eyes on them, and regroup in areas that are well clear of the runout of an avalanche path.  

It's been great to see all of the recent observations.  Keep 'em coming.  Add value to your forecast.  Submit an observation here.  

 

 

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