Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Mon
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

Winter will be making a return to the Cascades, bringing snow, strong winds, and dangerous avalanche conditions. Winds will drift snow into deep slabs, and new snow may not bond well with underlying surfaces. Avoid steep slopes and starting zones, especially in wind-affected terrain. The highest avalanche hazard and snow accumulations will be in areas closer to the Crest. 

Problemi valanghivi

  • Storm Slabs

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

    While snow accumulations will be light in areas further east from the Crest, such as Blewett Pass and Mission Ridge, areas further west in the zone could see up to a foot of new snow. New snow may not bond well with old, hard, and sometimes slick surfaces. The Valentines Day crust is now buried by a few inches of newer snow in some areas, and may still be on the surface further east. Observers found weaker snow beneath and sometimes above this thin crust in high, shaded locations during the week. These variable surfaces will create variable distribution in avalanche conditions. Use quick hand pits to investigate how the new snow bonds to the existing surfaces and watch for signs of instability such as shooting cracks, collapsing, and recent avalanches. Strong winds will accompany this storm and build deep wind slabs in open terrain at all elevations. These may form further downslope and even in areas below treeline typically sheltered from the wind. Use visual clues such as blowing snow, wind-textured surfaces, and cornices to identify wind-affected terrain. Sunday will be a good day to avoid steep terrain in wind-affected terrain and seek out lower angle sheltered slopes. 

    (12/8/2021) Long shooting cracks in freshly wind drifted snow

    Photo: Matt Primomo

Avalanche Discussion

While we are all looking forward to some long-awaited snowfall, the long warm, dry spell has created a lot of surface variability, and there is uncertainty on how well this snow will bond with these existing surfaces. Therefore, approach new terrain slowly with a conservative mindset and make observations as you travel. 

In eastern areas of the zone, challenging travel conditions on icy surfaces will be the main hazard. Observers have reported glazed over wind board and bulletproof surfaces on high, north-facing terrain. Sharp tools like crampons and an ice axe may be necessary for travel in some areas to prevent long uncontrollable slides. 

In some locations near the Crest, weak faceted snow may exist above or beneath crusts from late January/early February. Forecaster Irene Henninger found this weak structure near Holden about 5cm below the surface. Additional snow on top of this crust-facet combination or very slick crusts may create a persistent slab problem moving forward. Dig down, or document these layers while they're near the surface if you travel on shaded upper elevation terrain.

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