Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 2 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Additional avalanches Friday, in both wind-loaded terrain and on deeper layers, continue to emphasize this is not your normal post-storm weekend. You’ll need a high level of caution and restraint to not let powder fever pull you into bigger terrain. Consider staying completely off of all steep open slopes at middle and upper elevations.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    Shifting winds continue to build a complex patchwork of slabs on a variety of aspects. In some cases, you could find a wind loaded pocket on both sides of the same ridge, no matter the current wind direction. 

    Pay attention to changes in how the snow feels or how much is underneath you. Larger drifts, cornices, and the snow blown out of trees can also give you clues to local wind effects. You’ll most likely find wind slabs near ridgelines, along the base of cliffs, and in the tops of chutes. Steer around pillow-like piles of snow in steeper terrain. Given the variable loading pattern, sticking to sheltered terrain will be the easiest way to avoid this problem.

    At lower elevations and in sheltered areas, you're more likely to find lots of deep powder. Expect loose dry slides that could knock you over or push you into a tree. 

    (3/1/2024)

    A small but wide intentionallly triggered wind slab avalanche. NNE, 6500ft. 

    Photo: Dallas Glass

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–3

    There’s plenty of evidence that this problem is present and primed to create avalanches. Additional natural and triggered slides occurred near Crystal Mt on Friday, and snowpack tests near White Pass showed sudden results. If that’s not enough, an avalanche fatality (see below) likely occurred on these same older snow layers just across the border in the East South zone. 

    So far, avalanches occurred mainly above 5500ft on a variety of aspects (NW-SE). We know these layers generally formed everywhere, but several sunny days, wind events, and other storms radically upended the widespread distribution. It may be impossible to tell if any single slope could produce a slide. Even within local areas, the distribution may be erratic and unpredictable. 

    Unfortunately, the only real solution is avoidance. These slides would be very wide, deep, and deadly. Stay off of large startzones and limit any time you spend in their tracks and runouts.

    (3/1/2024)

    A deep avalanche near Bear Gap in the Crystal Mountain backcountry. [N 6200']

    Photo: Andy Harrington

Avalanche Discussion

Preliminary Report: An avalanche accident occurred on Friday, March 1 near Darland Mt in the Ahtanum Meadows area. Two snowmobilers were involved in the slide. One rider was fully buried and killed. The avalanche occurred around 6600ft in a generally east-facing bowl. NWAC staff will visit the accident site on Saturday. Our deepest condolences to the family, friends, and community.

Cold temperatures, more low-density snow, shifting winds, and periods of sunshine will describe Saturday. Despite the rather meager precipitation amounts, this bit of water could quickly become several inches of fluffy snow. While that won’t add much to the hazard, shifting moderate winds will continue to build slabs and drive the hazard. 

If the sun comes out for longer periods of time, temperatures could quickly warm. You may see snow shed from trees and rocks. The snowballs could trigger small loose avalanches in very steep terrain. 

Below the feet and feet of recent snow, a weak snowpack structure continues to lurk. Facets and surface hoar on the 2/19, 2/14, and Early February Crust could all produce avalanches. While most of the activity has been in the Crystal areas, seismically detected avalanches on Mt St Helens and very wide crowns observed on St Helens and Adams could also be failing on older snow layers. You can dig and take a look, but these layers are generally under 4-6+ft of snow, and a snow profile might not give you the full picture. 

We don’t have much data from Mt Rainier this week. If you’re in the Paradise area, be ready to make your own evaluations. All we know is there's been LOTS of snow and wind. 

With all this soft powder, deep snow emersion is a real hazard. Keep your partners insight and have a plan to communicate easily within your team.

Regioni coperte