Boletín de aludes

East Slopes North

Northwest Avalanche Center
Ver en el mapa

Peligro de aludes

Tue
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
2 · Moderado
Open full map
Desactualizado: este boletín caducó 2 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

A poor snowpack structure is prolonging dangerous avalanche conditions. You could still trigger avalanches on deeply buried weak layers. These slides are likely to break widely across terrain, and they can be triggered from a distance and catch you off guard from above. Avoid traveling on or directly under steep open terrain, especially at upper elevations.

Problemas de aludes

  • Persistent Slabs

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

    Over the weekend, observers reported numerous large and very large avalanches that failed and ran on deeply buried weak layers; see photo here and more below. Put a large buffer of terrain between your group and large start zones and complex avalanche paths above 6,500ft. Choose smaller, well-supported slopes and stay out from under large overhead terrain. If you see cracks shooting through the snow or feel whumphing collapses, stick to slopes under 30 degrees. A recent load from snow and wind has stressed the underlying weak snowpack structure. Look for strong-over-weak snowpack structure and sudden or propagating snowpack test results to help you identify the problem. The most problematic slopes will be where you find a thin, weak layer of facets over the Feb 25th interface (sometimes a crust 1-2.5' below the surface) and the Jan 31st crust, 2-4' below the surface. Observers reported very large natural avalanches in the past week. We suspect some of these ran on these layers. This same weak snowpack has already been the source of numerous close calls and one fatality in the Eastern Cascades.

    A very large avalanche was triggered by skiers on 3/2 on Kangaroo Ridge. This broke very widely and ran almost the entire length of the path. We suspect this ran on a persistent weak layer.

    Pk 8183, WNW, 7,600ft

    (3/2/2024) Photo: Willie Webster

  • Wind Slabs

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

    You're most likely to trigger avalanches in the recent layers of snow near the surface or where the wind has formed stiff slabs. Slopes below corniced ridgelines and the base of cliffs are likely locations for wind slabs to form. Look for pillow-like drifts or textured surfaces to identify wind affected snow. Small storm slabs or loose avalanches may also be possible on steep, wind-sheltered slopes. Take time to test the new snow on inconsequential slopes before traveling in terrain steeper than 35 degrees. Avalanches at mid and upper elevations could be unsurvivable. There, you must manage the more deadly consequences of persistent slab avalanches and avoid large avalanche terrain altogether.

    (12/22/2023)

    Example of cracks in recently wind-transported snow. 

    Photo: Willie Webster

Avalanche Discussion

Expect some light snow showers and moderate winds on Monday. We could see some sun breaks in the afternoon, and if they're long enough, we could see some wet loose avalanches or rollerballs on steep sunny slopes. 

Signs of instability have been abundant in the past week and dramatically so on Saturday. Multiple close calls and numerous snowpack observations in the Highway 20 corridor point to a couple of buried weak layers (2/25 and 1/31) in the top 2-4 feet of the snowpack. On Saturday, an NWAC observer witnessed another group trigger a widely breaking, very large avalanche on Kangaroo Ridge. It ran almost the entire length of the avalanche path. While we can't confirm, we suspect this ran on one of the persistent weak layers. More details on the Kangaroo Ridge avalanche can be found in the photo caption below and in this observation. In a sepereate event on the southeast sholder of Cutthroat Peak (6,400ft, SE) a party remotely triggered avalanches that propagated to either side of them 800-1000ft after leaving a profile site that they dug on the slope. A number of other very large natural avalanches have been reported, mostly from upper elevations, that appear to involve deeper weak layers.

On Thursday, a group of skiers near Cutthroat Lake (7,100ft, SE) felt a very large collapse and observed cracks that broke several hundred feet across and down the slope. While no avalanche occurred, a quick profile determined a weak layer of facets was 60cm down near a crust. Since Wednesday, observers reported a widspread cycle of avalanches, some up to size D3. While many avalanches likely occured within the recent snow from the last week, we suspect some may have ran on older weak layers. Earlier in the week, observers near Blue Lake found whumphing collapses and confirmed the instability was on a layer of faceted snow 2ft down above the late January crust.  

Snowpack information is limited outside of the Highway 20 corridor and Harts Pass. Let us know what you find if you get out into the backcountry!

Regiones cubiertas