Bulletin d’avalanche

East Slopes Central

Northwest Avalanche Center
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Danger d’avalanche

Sun
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Points saillants

The combination of strong winds and recent snow falling on weak snow surfaces makes for tricky, dangerous, and variable avalanche conditions. You could easily trigger large avalanches in wind drifted snow and be surprised by smaller avalanches in sheltered terrain. With this unusual snowpack setup, dial back your terrain and choose low-angle slopes. 

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Strong to extreme winds are forecasted to impact the zone from Friday night through Saturday. With fresh, low-density snow drifting onto weak or slick snow surfaces, wind slabs could be quite sensitive and break wider than anticipated. More snow will accumulate near the Cascade Crest, so areas like Salmon La Sac will hold the highest danger for large avalanches. Wind slabs may release naturally, so don't linger beneath steep open terrain at upper elevations. Avoid steep, wind-loaded slopes below ridgelines, cross-loaded gullies, and the base of cliffs. 

    High wind speeds could cause wind slabs to form lower in the terrain than anticipated. Look for deep drifts, textured surfaces, and visible blowing snow to identify steep, wind-loaded terrain to avoid. 

    (12/26/2024)

    An example of a widely propagating avalanche in wind-loaded terrain from earlier this season. 

    Photo: Mission Ridge Pro Patrol

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–1.5

    Sensitive storm slabs may be widespread on northerly terrain, particularly in open glades and meadows where recent snow fell on weak facets and surface hoar.  With this high level of uncertainty and variability, reign in your terrain selection and enjoy the return to winter on low-angle sheltered terrain.  With the highest snow totals near the Cascade Crest, avalanches are more likely to be larger in areas like Salmon La Sac. 

    The usual strategies and tricks you use to manage risk might not be reliable, given the variation in snowpack structure below the new snow. Some slopes might produce no avalanches or smaller slabs. On other slopes, even those adjacent, you could trigger unusual avalanches that propagate widely, release when you are in the middle of a slope, or might even be triggered from below. Be especially wary of skiing into steep open glades in northerly terrain. Even a small avalanche could push you into trees, rocks, or over cliffs. 

    (1/10/2024)

    A remotely triggered avalanche on weak, faceted snow from last season. You could trigger similar avalanches this weekend. 

     

Avalanche Discussion

Another stormy Saturday is in store with drastically colder temperatures, strong winds, and additional snow. We are continuing to load a very weak and variable snowpack. We might not be sure how these avalanches will be distributed with the widely varying old snow surfaces, and adjacent slopes could have very different stability. Treat every slope as a suspect until we gain more information about the distribution of more lingering avalanche problems. 

The fresh snow is a welcome relief from the high and dry, but it also means taking a gigantic step back and choosing low angle conservative terrain. The bonus is that with minimal new snow further east, low-angle terrain helps keep you off the underlying crusts and can offer better recreation! The current snowpack is highly variable and exceptionally weak in many areas. You can find deep layers of weak facets on north and east aspects at all elevations. A NWAC Forecaster even found faceted snow all the way to the ground at Blewett Pass on Thursday. Other slopes also have facets, breakable or supportable crusts of varying thickness, or hard wind-affected snow.  As these conditions will be hard to assess, manage the hazard like you would a persistent slab avalanche problem. Give yourself wide safety margins and understand that avalanches may break in surprising ways or wider than expected. 

Help NWAC Forecasters reduce uncertainty by submitting an observation. Your information will help us write more accurate forecasts!

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