Lawinenlagebericht

East Slopes Central

Northwest Avalanche Center
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Lawinengefahr

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

A few inches a day and light to moderate winds are maintaining heightened potential for wind slab avalanches at upper elevation, exposed terrain. Beware of the potential to trigger two flavors of slab avalanches; Large, older wind slabs and recently formed soft,  shallow ones. Be ready to back away from steep or unsupported slopes if finding wind stiffened snow, or signs of instability like shooting cracks.

Lawinenprobleme

  • Wind Slabs

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

    Identify the most likely areas to hold stiffer slabs as you gain elevation. You can use a ski pole or quick hand pits to feel for deeper, stiffer drifts of snow. Steer around areas of convexities and pillowed drifts on steep, open or unsupported slopes. If you observe any signs of cracking, then back off from entering steep slopes nearby.

    Shallow, actively forming soft slabs may be reactive during the day, but it's the chance of triggering a large old wind slab that is more concerning. Avalanches could be larger and easier to trigger above treeline, where old stiff wind slabs may still prove reactive to the weight of a person or snowmobile. Pay close attention to any terrain features that appear loaded by the wind. Both easterly and westerly winds have been drifting snow over the past week, so you could find them all around the compass. 

    (3/5/2023)

    Cracks in wind-stiffened snow are a sign of wind slab instability. Blewett Pass

    Photo: Matt Primomo

Avalanche Discussion

The cool, cloudy, and showery upslope pattern continues to bring a trickle of new snow each day. Observers report that the recent snow is generally uncohesive, with isolated areas of stiffer wind slab. On Friday an observer triggered a small soft slab on a convex rollover in the upper Icicle Drainage. It ran on a thin sun, recent suncrust about a foot down. While this potentially problematic layer may be isolated in distribution, it could produce avalanches as the new snow settles, and gains cohesion. 

There has been steadily accumulating snow and light to moderate winds over the last 4 days throughout the zone. This soft snow rests over intermittent recent sun crusts (described above), and a pair of rain crusts from Valentine's Day, which is often 1-3ft deep. These often present as a crust/facet/crust sandwich, with weaker snow beneath the upper crust. Observations indicate quite a wide variability in the structure of this layer. There have been a couple of observations that point to instability on this layer in the Icicle drainage, though instability has been quite isolated in nature. One natural slab at 5,900ft on an ENE aspect on Cashmere may have run on it, and a couple of slabs in Stevens Pass zone (see Stevens Pass Forecast Discussion for details) ran  on it last week. If you get out into the mountains, submit an observation to share what you found.

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