Bulletin d’avalanche

Snoqualmie Pass

Northwest Avalanche Center
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Danger d’avalanche

Fri
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 2 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Thursday marks the beginning of an extended stretch of warm and sunny weather. Dangerous avalanche conditions may develop during the day with overlapping dry and wet snow problems. Travel conservatively and pay attention to changing conditions as well as your overhead hazard. 

Problèmes avalancheux

  • Loose Wet

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

    As the day warms up, look for the tell-tale signs on increasing wet loose instability like wet surface snow, pinwheels/rollerballs and natural wet loose avalanches.  It's the first big warm-up under a strong mid-March sun and we have about 2' of recent storm snow above 5000'.  Wet loose avalanches can become large at mid and higher elevations where they entrain the recent storm snow, especially in tight features like chutes and gullies.  Move to shadier aspects and lower angle terrain without exposure to overhead hazard like cornices and avoid traveling on or below cliffy slopes in the sun.  Wet loose avalanches are likely to be smaller at lower elevations, but can still cause trouble near terrain traps.  Breezy conditons may lower the likelihood of wet loose avalanches in some terrain, so continue to reassess not only over time but as you move through different terrain. 

    (3/18/2023)

    Wet Loose avalanches releasing  on sunny slope last March. Most of these slides originated near rocky terrain.

    Photo: Public Observation

  • Storm Slabs

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

    Convex rollovers and steep unsupported slopes are places where you might still trigger a storm slab avalanche.  While storm slabs should be healing overall, some aspects may be touchier than others where new snow has bonded poorly above a graupel layer or a thin crust.  Use quick hand pits and upslope tests to see how the new snow is bonding.  Signs of cracking in the new snow or recent avalanches are signals to avoid nearby slopes steeper than 35 degrees.  Recent storm slabs have been shallow, but could be deeper and more consquential at upper elevations and in wind-loaded terrain. 

    (3/13/2024)

    Use small test slopes to look for signs of instability in the new storm snow. 

    Kendall AZ.  

    Photo: Cal Wilkes

Avalanche Discussion

A stormy few days came to an end on Wednesday, with 2.6" of water equivalent translating into about 2' of snow above 5000' and about half that at Pass level as snow levels bumped around 3000'.  Backcountry travelers found evidence of small natural avalanches both Tuesday and Wednesday that likely occurred during higher loading rates.  Cracking and skier triggered slab avalanches were reported in the top 4-12" of snow on both Tuesday and Wednesday.   

Persistent slab avalanches are front and center in neighboring zones. We do not have any confirmed avalanches at Snoqualmie Pass on the Early February Crust (EFC) or the associated interfaces, but that doesn’t mean it’s out of the realm of possibility.  Any avalanches down to the EFC would be very large and destructive.  Keep these deeper interfaces in mind as we move deeper into a multi-day warm-up and the likelihood of an "improbable" very large avalanche starts to tick upward. 

Régions couvertes