Lawinenlagebericht

West Slopes North

Northwest Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

You can still trigger a large avalanche in wind drifted snow at upper elevations. Ease into terrain slowly and avoid unsupported slopes 35 degrees and steeper with evidence of wind loading. Periods of sunshine and warming Tuesday may allow wet avalanche activity to continue.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Wind slabs developed in the 2+ feet of new snow since Thursday, and are still reactive to human traffic at upper elevations. Several triggered wind slabs up to size D2 were reported Monday, including a close call on Shuksan Arm where a snowboarder was caught and carried. These add to the list of human-triggered and natural wind slab avalanches from the weekend.  Fortunately, there were no full burials or injuries. Avalanches in wind drifted snow could break 6in-3ft deep on a variety of mid-storm interfaces or on a crust that formed up to 6000ft on March 4. Continue to approach upper elevation terrain cautiously. You are most likely to trigger a wind slab in northerly terrain steeper than 35 degrees, especially on convex or unsupported slopes. Use extra caution around ridgelines or any slopes where cornices exist. These unpredictable features are large and overbuilt and can break further back than you may expect or fall onto slopes below acting as huge triggers. Seek out terrain less than 35 degrees where you find recent avalanches, cracking, collapsing, or evidence of wind drifted snow. 

    (3/8/2021) A snowboarder-triggered avalanche on Shuksan Arm that broke 1-3ft deep, 200ft wide, and ran 300 vertical feet. The snowboarder dropped the cliff above the slope and triggered the avalanche upon landing. They were caught and carried but remained on the surface with no injuries. Photo: Pete Durr

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Loose wet avalanches may continue to run naturally and even grow large during periods of sunshine on Tuesday. Cloudy skies at times may delay loose wet activity, but it may not take much solar radiation for snow surfaces to become wet and weak. The sun is high in the sky this time of year, and so much stronger than it was just a few weeks ago. Watch for changing conditions throughout the day on sun-exposed slopes. You may see snow shedding from trees and rocks first, and rollerballs and pinwheels following soon after. When you see these clues, think loose wet avalanches. Steer around similar slopes and seek out more shaded terrain to avoid the problem.  

    (3/8/2021) Small point releases and rollerballs in southerly terrain on Mt. Herman. Snow surfaces warmed up in the strong March sun by mid-morning on Monday. Photo: Alyssa Young

Avalanche Discussion

From March 4-7, over 2ft of new snow accumulated above 4000ft throughout the West North Zone. Skies cleared on Monday, and intense solar radiation and warming temperatures affected cold snow surfaces causing rapid settlement and wet loose activity. Several wind slab avalanches were triggered in upper elevation terrain on Shuksan Arm and in Bagley Basin. Most were small and predictable, but some broke deeper, wider, and grew large including a recent natural avalanche in Hidden Bowl (photo below). Over the weekend, a small human-triggered avalanche occurred in 5 Minute Trees, a slope that already had several tracks on it from the same day. It caught and carried the rider, burying them to their knees. Nearby, a large natural avalanche was observed in Blueberry Chutes, and it is suspected to have been triggered by cornice fall. 

Snow and avalanche conditions are variable in the West North zone and throughout the Cascades in general. There are dormant layers (mid-January PWL) in our snowpack buried over 10ft deep that produced a widespread avalanche cycle in the Hwy 542 and Hwy 20 corridors in early February, and isolated natural avalanches during heavy loading events throughout the month, as recently as February 25. Although the weight of a person may not be enough to trigger an avalanche on this layer, a large cornice fall on the right slope and in the right spot may do the trick. The transition to spring also adds uncertainty, and we continue to track this layer throughout the region. Even though it is not enough of a concern to list as an avalanche problem in the West North zone at this time, a significant weather event could potentially reactivate the layer. Keep this in mind looking ahead, and consult the West Central or Stevens Pass Forecasts if you plan to travel in areas along Hwy 20. 

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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