Bulletin d’avalanche

Snoqualmie Pass

Northwest Avalanche Center
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Danger d’avalanche

Wed
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Points saillants

A springtime storm will deliver rain, snow, wind, and fluctuating freezing levels to Snoqualmie Pass. This could result in unusual avalanches that obscure the boundaries between wet and dry, slab and loose. When in doubt, your best bet will be to avoid slopes over 35 degrees where triggering an avalanche is more likely.

Problèmes avalancheux

  • Loose Wet

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

    This should be a relatively warm storm. Mixed precipitation, a poor overnight freeze, and other springtime factors will combine to create a weak and wet snow surface capable of producing avalanches. These slides typically start near a point and fan out as they move downhill, possibly growing large in the process. With a crust just below the surface, slides could run far or even fail in a more slab-like manner than you might anticipate. Wide swaths of moist snow could move downhill in a way that's not quite loose but not quite slab. Regardless of how you want to label these avalanches, they'll be more likely on slopes over 35 degrees. If the sun pops out in the afternoon, their distribution could expand onto upper-elevation slopes.

    (4/7/2024)

    Wet avalanche debris piled up against trees. This avalanche was triggered by skiers descending a steep slope. You can tell that the snow surface is heavy and moist.

    Photo: Aidan Crawford

  • Storm Slabs

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

    As you ascend above the rain/snow line, you'll hit a messy transition zone and then start to encounter a more winter-like scene. Heavy new snow, gusty winds, and fluctuating freezing levels will result in new snow problems to manage. These may not be your classic storm slabs or wind slabs, but some mutant child formed with wet snow. Use quick hand pits to examine the snow over the Early April Crust (4/2). Take note if you find heavy snow over weak snow or poor bonding. Use uptrack tests and small slopes as you travel to gain information about how the new snow is reacting to your weight as a traveler. If you see cracking of the surface, blocks of snow failing in your tests, or observe signs of wind-loading, avoid slopes over 35 degrees where triggering a slab is more likely.

    (4/7/2024) 

    A skier-trigger avalanche in recent storm snow. This one blurs the lines between wet and dry, loose and slab. [Roaring Ridge]

Avalanche Discussion

The bulk of this storm will impact Snoqualmie Pass overnight, Monday into Tuesday. That means you should contend with the highest potential for avalanches right out of the gate on Tuesday morning as the storm dwindles. The winds are strong with this one and may keep things cooler than expected. Use the forecast as a launching point for planning your day, and be prepared to make your own observations based on how the weather is unfolding. Wet avalanche activity could be reinvigorated if the sun pops out in the afternoon.

As you ascend in elevation, avalanche problems should transition from wet to dry, with a messy zone where you could find both right in the middle. Some may even blur the lines between wet and dry, loose and slab. Regardless of moisture content and characterization, the majority of avalanches should be confined to the snow above the Early April Crust (4/2). This interface should be easy to find when digging with your hand or shovel. Numerous wet avalanches were reported this weekend in the snow above this crust.

With spring weather, the threat of shed-style avalanches is a constant. Keep an eye on the terrain above you and limit your time spent below hanging blocks of snow, sagging cornices, or slopes with large cracks. That snow all has to come down at some point.

Lower elevations contain relatively low snow coverage. But where adequate snow exists, small avalanches are possible. More likely, you'll need to manage travel hazards. Open holes/creeks, shallowly buried rocks, and refrozen avalanche debris are more prevalent down low, but they litter the landscape at all elevations. This storm will only exacerbate these problems. Give yourself extra time and bring the tools required to travel safely.

Régions couvertes