Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

Another springtime warm-up is on our doorstep. Expect wet avalanche activity to increase as sunshine and warm temperatures combine to destabilize the snow surface. If the snow surface is wet and weak, head for shadier slopes and be aware of terrain above you that could be baking in the sunshine.

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–1.5

    We're entering another warm and sunny period, meaning wet avalanches should be at the forefront of your mind. On Saturday, sunshine and daytime warming will be the significant drivers in creating the conditions required for wet avalanche activity. Once the snow surface becomes wet and weak, you'll start to see rollerballs, pinwheels, and eventually wet avalanches. We expect the majority of these slides to be loose avalanches, which often start at a point near rocks or trees. They can grow large and powerful as they descend and gather snow. In some areas, they could even trigger slabs. Your best management tool will be to stick to shaded slopes to avoid these difficult to predict slides.

    In isolated locations, larger, more unpredictable shed-style avalanches could occur. Cornice collapses, glides, or even wet slabs could happen over the next few days. Keep an eye on the terrain above you, and don't linger where you see precariously hanging blocks of snow.

    (3/29/2024)

    A wet loose avalanche that gathered snow as it traveled downhill. It started at the base of cliffs.

    Photo: Patrick Stanton

  • Wind Slabs

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

    At upper elevations, drier snow and the potential for slab avalanches exists. They could be found on any aspect in the morning but may be confined to shaded slopes by day's end. You're more likely to trigger one in wind-loaded terrain. Look for visual clues such as textured surfaces, smooth pillow-like drifts, or new cornices to help identify wind-loaded features. Wind slabs commonly form in confined chutes, on convex rollovers, or near the base of cliffs/rocks. Using small test slopes can give you information about how these slabs may be reacting to your weight. If you suspect a slope is wind-loaded, choose a different route.

    (3/29/2024)

    Wind effect was observed throughout the week. Look for wind slabs near rocky terrain or ridgelines.

    Photo: Caya Johnson

Avalanche Discussion

Bring on the sunshine! We've recently been through this scenario, but this time around, it shouldn't get quite as warm for quite as long. Even though our last warm-up may be fresh in everyone's mind, let's break down what's expected to happen.

We've had a week of snow showers with fluctuating freezing levels at the Pass. This has resulted in high-elevation dry snow and lower-elevation moist/wet snow. Of course, there's a transition zone at middle elevations where you'll likely find a mix of avalanche problems and moisture content. Alpental Pro Patrol and backcountry travelers have reported both dry and wet avalanche problems in recent days. A surface crust will likely exist on Saturday morning on sun-exposed slopes but should break down throughout the day.

As we march into a warmer and sunnier weekend, the dry snow problems will slowly diminish while the wet avalanche problems intensify. Wet avalanches are notoriously challenging to forecast peak instability, and the problems can be intermingled. We could see the mountains start to fall apart on Saturday, or it may not happen until Monday or Tuesday. So stay vigilant and know that it's likely coming at some point over the next few days. 

Roughly 1-2 feet below the surface, you'll find a crust from the big warm-up a few weeks ago. We anticipate most avalanche activity to occur above this easily identifiable interface during this event. It could make a good sliding surface for wet loose to gather additional snow and increase in size.

Our snowpack has taken a beating at lower elevations, and the warm and sunny weather won't help. You'll likely find punchy wet snow, patchy coverage, and exposed creeks/holes. Avalanche potential may be minimal, but you could see activity at the upper end of the lower elevation band.

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