Bollettino valanghe

Stevens Pass

Northwest Avalanche Center
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Pericolo valanghe

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

Wet snow falling on moist snow surfaces creates conditions for triggering small wet loose avalanches below around 5000 ft.  Once you move into drier snow, observe signs of wind transport on the shaded or lee sides of ridgelines. Pay attention to changes with elevation and aspect, steering away from open slopes 35 degrees or steeper if you suspect a problem.

Problemi valanghivi

  • Loose Wet

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

    You're likely to find about 6" of moist or wetted snow above the stout melt-freeze crust.  This snow layer has been fodder for 3-6" wet loose avalanches that proved capable of taking a skier for a ride on Saturday. We're not talking about the types of gauging slides we saw in late March. Activity should be entirely above the stout crust. Remember that radiation getting through thinner clouds or wet snow falling will add to the problem. If you encounter more than 4" of moist, sticky, or wet snow on Monday, reduce your slope angle to less than 35 degrees.

    (4/6/2024) Photo: Jon Sullivan

  • Wind Slabs

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

    You can trigger a small slab near ridgelines and where winds have a chance to redistribute cold snow from shaded aspects onto lee slopes. Several inches of snowfall, primarily arriving during the afternoon, will redistribute in wind-exposed areas, adding to the slabs. In general, your risk increases at higher elevations and on shaded aspects. Look for clues like textured surfaces, sharp wind lips, and fresh drifts to point toward a potentially loaded slope. Although these wind slabs may be growing, these wind slabs should be relatively small and easier to identify and steer around. Give a little extra margin for error when above terrain traps such as cliffs or gullies.

    (4/7/2024) 

    Wind slabs within shallow, dense slabs of drifted snow. White Pine.

    Photo: Logan Heine

Avalanche Discussion

The sun's energy, limtied overnight cooling due to cloud cover, and warm daytime temperatures proved sufficient to make wet loose avalanches the primary concern on Saturday and Sunday, despite snowfall down to pass level or below. 

We're expecting a bit of cooling Sunday night, but mid-level clouds will limit radiative cooling once again. It won't take much daytime warming on Monday to break down shallow refreezes at lower and possibly middle elevations. Light rain and snow will increase in the afternoon, contributing wet sticky snow or perhaps even rain on snow to exacerbate the problem. At upper elevations and in areas exposed to the fetch of wind off colder snow, you'll find pockets of wind slabs near ridgelines. Everything is small and manageable, but don't let your guard down as you change aspects and switch problem types. Even a small avalanche in a higher consequence location could ruin your day.

Over the past few days, Stevens received about 4-8 inches of snow, which accumulated on a firm crust. In general, we’re only concerned about this surface snow. On Friday, a backcountry traveler on Lichtenberg triggered a small loose slide where the new snow seemed to run easily over firm underlying surface. Below this shallowly buried crust, the snowpack is strong, but still transitioning from winter to spring. 

Sunny and warm weather over the past several weeks took its toll on the snowpack, particularly at lower elevations.  Now, you're likely to find thin coverage, exposed obstacles, open holes, and flowing creeks. Additionally, firm surfaces and frozen debris/rollerballs/ tracks/tree bombs frequently make travel trickier than normal. Give yourself extra time to navigate these springtime challenges.

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