Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
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Pericolo valanghe

Tue
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 2 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Wind-loaded features were the culprit in numerous human-triggered avalanches over the weekend and should be avoided on Monday. You have a higher chance of triggering an avalanche as you ascend in elevation. Wind slabs like to form near ridgelines, on convex slopes, or in confined chutes. 

Problemi valanghivi

  • Wind Slabs

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

    Winds have been blowing from all directions the last few days, meaning slabs could exist on various aspects. You could find a wind-loaded pocket on both sides of the same ridge.  New shallow slabs may develop during the day, or older ones could be hidden under the surface. So, pay attention to changes in the density and depth of the snow as you travel. Firmer or thicker areas are likely wind-loaded and should be avoided. Visual clues such as fresh drifts, cornices, and textured surfaces can give you clues to local wind patterns.  Since the shifting winds and fresh snow may make these slabs challenging to locate, your best bet is to identify common features where wind slabs like to form and avoid them. They'll be more likely near ridgelines (example), along the base of cliffs (example), on convex rollovers (example), and at the tops/sides of chutes (example).

    In wind-sheltered areas, the low-density snow could result in dry loose avalanches on steep slopes. Don't get tripped up by one of these sluffs and pushed into a terrain trap.

    (3/2/2024) Avalanche crown from below. Triggered near the littlest tree to looker's right of skiier.

Avalanche Discussion

Our persistent weather will continue on Monday, with more low-density snow, an uptick in wind speeds, and shifting wind directions. Sun breaks could occur between convective snow showers. If they're long enough, expect increased avalanche activity on slopes that see direct sunshine. 

The magic elevation at the Pass appears to be around 4500 feet. Below this elevation, up to a foot of recent storm snow sits above a stout crust, resulting in minimal avalanche potential. Near road level, the snow may even be moist.

As you ascend above ~4500 feet, the crust dissipates, giving way to deep powder and wind-effected features. Not surprisingly, avalanche hazard increases as you cross this threshold. There were numerous human-triggered avalanches reported over the weekend on wind-loaded features. Some wind slabs may still be reactive on Monday, or shallow new ones could develop as wind speeds increase. Although the recent storm snow is generally right-side up and settling, a few interfaces may still be capable of producing avalanches. 

While most of these concerns are related to the upper snowpack, it’s worth noting that most of our neighboring zones are dealing with a persistent slab problem (East Central, East South, West South, Stevens Pass). In these areas, slides are failing on deeper layers at or just above the Early February Crust (EFC). We do not have any confirmed avalanches on this layer at Snoqualmie Pass. However, you should at least consider the possibility of a very large persistent avalanche if you're heading for big open slopes. On Sunday, NWAC forecasters found the EFC 5 feet below the surface in the Kendall area. That would be quite the destructive avalanche if it failed.

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