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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In sintesi

Recent human-triggered avalanches, a known weak snowpack, and an ongoing winter storm tell you everything you need to know about Saturday’s dangerous avalanche conditions. Even though the storm totals might not seem impressive, this isn’t a day test your luck. Steer around steep open slopes, especially on more shaded aspects.

Problemi valanghivi

  • Wind Slabs

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

    First thing in the morning, any wind slab you encounter will likely be rather thin and not very dangerous. However, as the day continues, these possible avalanches will only grow deeper and more common. Because these slabs are actively forming during the day, they should be pretty easy to find. Blowing snow and areas with deeper deposits will help you figure out which aspects and features could hold new winds slabs. Steer around frim pillow-like drifts to avoid this problem. You could find these slabs near ridge crest, the sides of gullies, and near the base of cliffs. These slides may be the largest in locations that receive the most snow and at upper elevations. Wind slabs could act as the trigger for deeper and larger persistent slab avalanches.

    (3/15/2022)

    Example: Signs of the wind drifting the snow into deeper piles near ridgelines were observed near White Pass on 3/15.

    Photo: Dallas Glass

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–2.5

    The growing list of human-triggered persistent slab avalanches from all areas of the West South zone this week is the most compelling piece of evidence regarding this problem. While you may not see obvious signs of instability and there may already be tracks on the slope, recent avalanches trump these other observations. Weak sugary facets sit just about the very prominent Early March Crust. These persistent grains are commonly found on NW-NE slopes but were observed on other aspects near Paradise. This isn’t a problem to try to outsmart. These slides could trigger remotely from flat terrain above or below a start zone. With the addition of more snow Saturday, these potential avalanches may only be easier to trigger. Give steep slopes a wide berth if you’re traveling in terrain where this problem is thought to exist.

    (3/18/2022)

    A skier triggered avalanche on Mazama Ridge near Paradise, Mt Rainier NP. 16" deep. W aspect, 5600ft. This avalanche faild on the 3/8 facets over the Early March Crust. HS-ASu-D2-R3-O

    Public Field Report: Mount Rainier National Park, Mazama Ridge

    Photo: Public Observation

Avalanche Discussion

A winter storm should arrive in the West South zone in the wee hours of Saturday morning. This will drive dynamic avalanche conditions during the day with the hazard likely peaking in the afternoon. While we expect the most snow near the volcanoes, with a persistent weaklayer present all across the zone, don’t expect the danger to be lower just because where you’re traveling somewhere with less new snow. 

On Friday a skier triggered a persistent slab avalanche near Paradise at Mt Rainier. This avalanche only adds to the list of similar avalanches at White Pass and Crystal Mt on Wednesday. We know prior to recent storms a layer of 1-2mm faces were buried (3/8) over the very stout and prominent Early March Crust. This snowpack marker is easy to find with your probe, shovel, or even hand. While snow profiles and snowpack tests can confirm the presence of these persistent grains, they can not prove their absence. Remember, the recent avalanches are the most compelling information you possess. 

Outside of wind-affected terrain, we expect the new snow to bond well to the relatively warm surface from Friday. At lower elevations, rain may create wet avalanche conditions in a few isolated locations, but cooling temperatures should quickly put an end to these concerns.

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