Avalanche forecast

West Slopes Central

Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Wednesday will be warm, with sun and a light breeze, but we're just one day out from a lengthy storm culminating with 1-2+ft of snow on Tuesday, so don't let your guard down. We're not sure how easy it will be to trigger a dangerous avalanche in the new snow, so start small and avoid large, steep, unsupported slopes, especially ones that are wind-loaded or above terrain traps. Expect natural and human-triggered wet avalanches on steep, moist surfaces on the southern half of the compass as the day warms up. 

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Recently formed wind and storm slabs may remain reactive on their second day, although we're uncertain how exactly they'll behave. Increasing temperatures could improve stability, or they could cause more "slabby", cohesive surface layers that could avalanche - maybe even without a human trigger. Expect a change in slab reactivity during the day, possibly leading to an improvement in stability, or maybe the other way around. Don't let the blue skies lull you into a false sense of security without having throughly investigated the new snow layers. 

    Use small test slopes and smaller features to test reactivity. Search for any "upside down" feeling snow underfoot or with your hand. If you're on foot, skis, or snowshoes "upside down snow" is not as pleasant for travel, with a firmer surface layer and softer, punchier snow beneath. If you notice this, avoid nearby slopes with these characteristics greater than 35°. In general, avoid large, steep, unsupported slopes while the snow continues to settle the day after the storm. Also, steer clear of slopes above terrain traps. 

    Snow may still slide whether it's been wind-affected or not, although smooth or textured, firmer wind slabs - usually near or around rocky outcroppings, on the side of steep rollovers, and in gullies- are suspect for remaining reactive longer than non-wind-loaded features. 

    Example photo: A small test slope with a small wind slab was reactive to a human trigger. Use small features like these on Wednesday to check for reactive pockets. Even if you don't see results as obvious as this, that doesn't mean that a large, convex, unsupported slope might not slide. 

    Photo: Kyle Wyatt

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    It's going to be a warm, sunny day on Wednesday. Expect wet loose avalanches to run on steep slopes facing the sun, progressing from east, around to the south, and then west in the afternoon. Late February means the sun is going to be more intense and could surprise us with larger avalanches that could happen sooner than expected, especially if slopes have light, fluffy snow on them. 

    Pay attention to the sun's progress and its impact on the steep slopes facing it. If you see rollerballs, small slides, or notice the soft snow getting heavy and sticky, it's time to shift to shadier slopes or stay in lower-angle terrain away from steep slopes. 

    Example photo: Expect small and large wet avalanches, possibly first only behaving as rollerballs, on steep sunny slopes on Wednesday. 

    Photo: Julz Holder - Grounding Truth

Avalanche Discussion

A warm day and recent snow means a cornice fall isn't out of the question, which could result in a slab avalanche on an underlying steep slope. Likewise, a wet loose avalanche may, in turn, trigger a slab avalanche if it adds enough weight to a slope. Most slabs will probably be around 1-2ft deep, the depth of the most recent new snow layer. 

Water totals since Friday reached 5 - 7 inches throughout the zone, with over 2 inches arriving during the day on Tuesday. At least 3ft of new snow likely sits at higher elevations, but lower elevations received much more rain than snow, with snowlines receding rapidly over the last few days, now sitting at almost 3500ft. As a result of the weekend's warm portion of the storm, several large (D2-2.5) wet slab avalanches and a few very large (D3-3.5) avalanches that stepped down into deeper, old snow layers resulted in neighboring zones.

Nearby zones reported natural and human-triggered avalanches on Tuesday in storm and wind slabs, and mainly failing in the most recent snow layer 1-2ft deep. 

If you choose to travel onto steep slopes on Wednesday, be sure to have a partner, travel one at a time, have a transceiver, shovel, and probe, and be well-practiced with them. They won't do much good if you haven't been training and your partner's buried. 

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