Lawinenlagebericht

Stevens Pass

Northwest Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

The powder snow is adding up, but you could trigger avalanches at all elevations on Sunday. Wind slabs may be triggered in upper elevation, steep and drifted terrain. Loose snow may sluff during periods of heavier snowfall or on slopes that receive sun. Travel cautiously, and heed signs of instability in the deeper snow.

Lawinenprobleme

  • Wind Slabs

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

    Winds should continue to drift snow through Saturday night before easing on Sunday. Slabs were reactive in freshly drifted areas on Saturday, but other ones were not. Suspect wind slab in open, exposed slopes, and they may or may not release with a trigger. Slabs may be thicker and more cohesive in heavily wind affected terrain at upper elevations. They may be more likely to release in very steep and/or unsupported areas.

    Look for active wind transport or areas of recently drifted snow as you travel. Some areas may be able to easily identify with surface texture, others may be obscured by newer snow. If you observe shooting cracks in drifted snow, then be sure to avoid steeper or consequential slopes. Consider areas that get enhanced wind loading such as steep slopes near low points on ridgelines, and cross drifted raised features mid-slope. Cornices may be fragile from recent growth, and could break under the weight of a person. Make sure to stay well away from the edge of them.

  • Loose Dry

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

    New snow is adding up, and may sluff easily on steep slopes. Loose instabilities could be split up into two types on Sunday- those that involve cold snow on steep shaded slopes, and those that involve snow that is warming up on slopes that receive the sun's energy.

    For slopes that stay cold, remember that instability may be greater during times of heavy snowfall. Very steep slopes beneath cliffs may run during periods of heavier snowfall.

    For slopes that warm up, instability may rise by afternoon with daytime warming. These slides may also pack more of a punch, with heavier snow that entrains.

    In either case, watch your runout zones. Consider your terrain choice, and the consequences of small slides.

    Example sluffs from the West North zone on Saturday.

    Photo: Lee Lazzara

Avalanche Discussion

We're back into a colder, and snowier pattern for a while. Observers found 8-12" of new snow above 4,500ft near Skyline on Saturday, and less further east near Lichtenberg. Small sluffs were reported by a couple different parties on steep slopes that warmed up with the sun's energy passing through the clouds. A few graupel layers in the storm snow made for short lived periods of instability with isolated cracking and sluffing during heavier snow showers. Strong westerly winds transported snow on leeward slopes, and upper elevation westerly slopes were blown clear to the crust. This frozen crust may be at the surface in other exposed, windward locations and may make for slick travel in those areas. There aren't any deeper layers of concern beneath this crust (for the time being), as much of the snowpack has been through numerous freeze/thaw cycles and has transitioned over to spring-like wet grains.

Last week we saw a pronounced warming event, with a number of wet loose avalanches up to D2 observed on the pass. Most surfaces become moist or wet. A recent storm ending on March 5th dropped 2-3ft on Stevens Pass. On the 5th, a 3ft deep wind slab was triggered with control work that ran on the early April crust on a SE aspect. If you're in the mountains, submit an observation and let us know what you see, because springtime is a dynamic time for snow.

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