Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
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Pericolo valanghe

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

Dangerous avalanche conditions will continue during a prolonged warm-up.  Avoid traveling on or below complex terrain as the day warms.  Natural or human triggered wet loose avalanches/cornice fall may trigger slab avalanches on the slopes below. 

Problemi valanghivi

  • Storm Slabs

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

    Storm slabs are trending towards unlikely, but continue to use caution around convex rollovers and steep unsupported slopes.  While storm slabs should be healing overall, some aspects may be touchier than others where recent 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.  Recent storm slabs have been shallow, but could be deeper and more consequential at upper elevations and in wind-loaded terrain. 

    (3/14/2024)

    Storm layers were still visible in the recent storm snow with a shovel tilt test. 

    Photo: Aaron Richards

  • Loose Wet

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

    As the day warms up, look for the tell-tale signs of increasing wet loose instability like wet surface snow, pinwheels/rollerballs and natural wet loose avalanches.  A poor overnight refreeze followed by warmer temperatures on Friday may break down surface crusts more quickly. 

    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.  Loose avalanches or cornice fall could rip out a slab avalanche on steep slopes below. 

    Wet loose avalanches are likely to be smaller at lower elevations, but can still cause trouble near terrain traps. Breezy ridgeline winds may lower the chances or delay wet loose avalanches on some slopes, but it should not change how you approach your travel plans on Friday.    

    (3/14/2024)

    Slopes that are safe in the morning, may not be as the day warms and the sun moves across the sky.

    Natural wet loose avalanches covered skin tracks by early afternoon in the Alpental Valley. 

    Photo: Aaron Richards

Avalanche Discussion

The "hot" weather has started and backcountry travelers noted widespread wet loose (mostly small, but a few large) on Thursday in the Snoqualmie Pass backcountry/Alpental Valley.   Numerous storm slabs were visible in the surrounding terrain from earlier in the week.  Most were natural slab avalanches, but a few were skier triggered including one that ran over cliffs and onto a recently used skin track on the slopes below.  Overhead hazard will be a key part of safe travel over the next few days as the temperature warms up and snow falls down. 

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.  It's been quiet in the Snoqualmie Pass area without any recent avalanches on the Early February Crust (EFC) or the associated interfaces. Keep these deeper interfaces in mind if you're planning weekend travel and the likelihood of an "improbable" very large avalanche starts to creep up over time.  

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