Lawinenlagebericht

West Slopes Central

Northwest Avalanche Center
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Lawinengefahr

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

Winter's making a comeback and previously wet snow surfaces will freeze, plus you can expect to see 6-10" of snow fall Tuesday night and through to the end of the day Wednesday. It may be hard to believe but it's time to think about new dry snow problems, where wind drifted snow could deposit up to a foot or deeper. Avoid heavier and thicker deposits on steep slopes. 

Lawinenprobleme

  • Wind Slabs

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

    It's going to be cold, windy and snowy on Wednesday. We're going to get enough new snow, about 6 inches over night and then another couple inches during the day, that dry snow avalanche problems are back on the menu. Avalanche danger has been moderate for days now, but this is a different kind of moderate from previous days. Wind will likely deposit snow into stiffer slabs that could react to a human trigger.

    These slabs will be deposits over what we expect to be a firm underlying layer. With these shallower amounts, you can easily use your hand to dig down to the underlying layer and check bonding between the new and old snow surface, or see if there are any stiffer wind slabs at the surface that will easily slide on the layer beneath it. You can use small test slopes to see if drifts slide.

    You're likely to find wind drifted slabs around terrain features like rollovers, rocky outcroppings, and in gullies. You may see textured surfaces or feel thicker, or hollow snow beneath your feet.  Some drifts could be subtle, hard to differentiate from nearby non wind-affected snow. Avoid travel on slopes steeper than 35° where you identify wind drifts on Wednesday. 

    Although we don't expect slides to get very large, areas where you should be most concerned about triggering an avalanche is in high consequence terrain. This could be the case if you trigger a slab that knocks you off your feet above a cliff band, or you're caught in an avalanche that will carry you into trees, rocks, or a gully (terrain traps), amplifying the effects of even a small avalanche.

    Example photo: you might be able to trigger wind slabs on test slopes like this one on Wednesday.

    Photo: Irene Henninger

Avalanche Discussion

We're unsure exactly how this incoming new snow will behave. We hope that snow will bond well to the previously wet, warm, layer, but maybe snow will slide easily on the underlying layer or in new drifts. We expect a crust to form eventually, sooner or later in the old snow surface. 

Despite the usual irregular spring wet avalanche activity slowing with this rapid cooldown, it doesn't mean all activity will shut off overnight. A glide avalanche or cornice fall still might happen as temperatures cool. Continue to travel with haste beneath these features. Small wet loose avalanches, or more likely rollerballs, may happen at lower elevations, especially at the snowline interface where new snow may be moist. In these areas the old wet snow layer may not have much of a crust, so there's a chance some of the old snow could become entrained in a slide.

Snowline is rapidly receding from lower elevations. Most areas down low won't have much of a base beneath this new snow layer, but some deposits may still slide with an underlying smooth surface. Beware of hidden holes and other features under the shallow new snow surface. At all elevations beware of old avalanche debris deposits hidden under the new snow layer. 

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

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