Lawinenlagebericht

Stevens Pass

Northwest Avalanche Center
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Lawinengefahr

Thu
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

We're in for another beautiful early March day with sun in the morning, and clouds in the afternoon. Deep persistent slabs remain active above 5,800ft. You can still trigger one of these dragons in unsupported terrain, so identify heavily loaded or unsupported features you'll want to stay away from. Expect snow surfaces to become moist, and you could trigger wet slides on steep slopes that face E-S-W. 

Lawinenprobleme

  • Deep Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2–3

    The heavy snow and wind loading from the last weak has been stressing a deeper weak structure. These layers consist of facets and crusts buried in early February or mid February. Avalanches that run on these layers can grow to become very large, as they're 3-4ft deep and can propagate widely across the slope. You won't get signs of instability before triggering one, as the layer is just too deep. Snowpack tests can identify the layers, but have become inconsistent from one slope to the next. You're best bet is to remain aware of the terrain around you, staying out of complex alpine terrain and off steep unsupported, or heavily wind drifted slopes. 

    This problem is more pronounced at upper elevations, and further east in the zone. Tuesdays large avalanche shows that they can still be triggered. 

    (3/5/2024)

    A large rider triggered deep slab on a W aspect of Jim Hill at 6,500ft. 

    Photo: Nate Hough-Snee

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–1.5

    Direct sun and slightly warmer temperatures may create wet loose instability on steep slopes. You can anticipate this problem by considering your aspect vs. timing of when you might be on any given slope. Look for signs of instability, like small rollers falling out of trees or small fan shaped slides. Feel for moistening snow surfaces on slopes in the sun. You can use test slopes to check and see how any given area might react. These slides should remain small, but may be able to entrain more than you'd think, especially in larger terrain features. 

    Example wet loose avalanche from last season.

Avalanche Discussion

We're in for another beautiful winter day with great riding conditions. A party of two skiers triggered a deep persistent slab on Tuesday on the W summit pyramid of Jim Hill, a NW aspect at 6,500ft. The slab was approximately 60ft wide and 3ft deep, and carried one skier approximately 300ft down the slope. The skier was partially buried, but recovered with only minor injuries. The strengthening March sunshine is starting to have more of an affect on snow surfaces. Plan your day to move away from slopes in direct sun, and keep checking for moistening snow surfaces as the day progresses. Since the 24th, the Stevens Pass area has received about 5" of water equivalent, and the snowpack gained 3-4 feet. 

At Skyline on Friday, forecasters found a crust/weak layer, just below the February 24th interface to show a high potential for propagation.  On Sunday I investigated a D2.5 (large) avalanche on Jim Hill at 6,200ft, NE. It failed on the weak, faceted snow above the Early February Crust. Another forecaster visited Big Chief on Sunday and dug several pits on different aspects around 5700ft. She found inconsistent results, yet both facets above the Early February Crust and the 2/24 layer were noted and produced test results (compression, deep tap moderate-hard) in some of the pits. 

Your avalanche, snowpack, or weather observations are extremely valuable to the avalanche community. Help create a more accurate avalanche forecast by submitting your observations here. 

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