Lawinenlagebericht

West Slopes South

Northwest Avalanche Center
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Lawinengefahr

Sat
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Veraltet — dieser Lagebericht ist last year abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

On Friday, you'll need to deal with new snow problems throughout the day. This could look a little different depending on where you are, but wind-loaded slopes, convexities, or steep unsupported terrain are likely locations to trigger a slab. If the sun is out for any length of time, it could destabilize the surface and kick off natural avalanche activity. 

Lawinenprobleme

  • Wind Slabs

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

    In wind-loaded terrain, the new snow is piled deeper, and could fail more easily on Friday, so it gets the nod as the official problem. But you could consider this a "new snow problem," like our friends in Utah would say. Wind slab, storm slab, snow heating up in the sun resulting in loose or slab avalanches - they all involve the new snow. Look for textured surfaces, large drifts, fresh cornices, or actively blowing snow to help determine wind-loaded slopes. Areas such as leeward ridgelines, the base of rocks, confined chutes/gullies, and convex slopes are all classic locations where wind slabs like to form. If you suspect a slope is wind-loaded, steer around it.

    That new snow could fail in other ways in sheltered areas such as loose or storm slabs. Use your uptrack tests, hand pits, and small test slopes to look for cracking of the surface or blocks of snow failing easily. If you get concerning results, dial it back and avoid all slopes over 35 degrees. These tests work well to assess wind-affected terrain as well. 

    (3/13/2025)

    Crystal Pro Patrol found mostly shallow avalanches in the new snow during their morning mitigation efforts. The exception is a deeper (~3') slab in a wind-loaded pocket below rocks. This deeper slab was triggered by dropping a cornice onto the slope.

    Photo: Crystal Mountain Pro Patrol

  • Loose Wet

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

    This problem also involves the new snow, but with a caveat. It will need the March sunshine to help kick it off. That's not a sure bet on Friday, but there could be enough clear hours midday that talking about solar-induced avalanches is worth an official problem.  If the sun is out, it could destabilize the surface, resulting in wet avalanche activity such as rollerballs, pinwheels, and natural avalanches. It could also help the new snow "slab up" and become more sensitive on steep slopes. If you feel the snow surface getting wet, consider heading for lower-angled slopes in the shade. Be sure you are aware of slopes above you that could be basking in the sun and shedding snow.

    (3/9/2025)

    Sun-affected snow that failed as loose and slabs earlier this week near White Pass.

    Photo: Paul Przybylowicz

Avalanche Discussion

Thursday's storm was a decent snow producer for the west south zone and certainly delivered plenty of wind. Weather stations around the zone recorded winds gusting 50-60 mph, easily strong enough to transport snow into slabs on leeward slopes. Legacy NWAC forecasters in the Crystal area observed cracking of the surface in wind-stiffened terrain, as well as variable depth of snow over our most recent atmospheric river (AR) crust. Across the street, the Crystal Pro Patrol reported mostly small avalanches during their morning mitigation efforts except for one larger slab that broke 3 feet deep after a cornice fell on a wind-loaded slope. White Pass Pro Patrol had a similar report, without the deeper slab. 

Friday should be a bit of a lull in the weather before we hop back in the storm track on Saturday. This week, we've had a steady trickle of reported avalanche activity as small storms have rolled through our zone. All reported slides have been confined to the storm snow above the AR crust. This easily identifiable snowpack marker gives you something to target when making your on-the-ground assessments. The depth of new snow varies considerably based on elevation and location within the zone. There may be as little as a few inches to as much as 2 feet. That's quite the spread - so you'll have to look at the layering and bonding often wherever you travel. In locations with more than a few inches of snow over a crust, you may find that the 3/9 interface fails easily in handpits or more formalized tests. In isolated locations, buried surface hoar could exist at this interface.

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