Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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In sintesi

Continued spring weather will maintain the possibility of wet avalanche activity on Easter. If the snow surface is wet and weak, hop onto shaded aspects to limit your exposure to these unpredictable slides. The longer this warm weather goes on, the larger and more dangerous avalanches could become. 

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    Wet avalanche activity will remain the primary concern on Sunday. The sun and warm temperatures will likely need to break down a surface crust. Once that happens and the snow becomes wet and weak, you'll start to see rollerballs, pinwheels, and eventually wet avalanches. We expect the majority of these slides to be loose avalanches, which often start at a point near rocks or trees. They can grow large and powerful as they descend and gather snow. In some areas, they could even trigger slabs. Your best management tool will be to stick to shaded slopes to avoid these difficult-to-predict slides.

    In isolated locations, larger, more unpredictable shed-style avalanches could occur. Cornice collapses, glides, or even wet slabs could happen over the next few days. Keep an eye on the terrain above you, and don't linger where you see precariously hanging blocks of snow. Give cornices plenty of space; they are notorious for breaking back further than you might expect.

    (3/30/2024)

    Wet avalanches on multiple aspects. A few small slabs can be seen that failed as a result of the loose slides. [Paradise area, MRNP]

    Photo: Alex DeGrave

  • Wind Slabs

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

    There could be some lingering slabs at upper elevations in areas still holding dry snow. You may even see some actively blowing snow or shallow new drifts, especially in high-elevation terrain where the winds could be strong on Sunday - such as the volcanoes. Wind slabs commonly form in confined chutes, on convex rollovers, or near the base of cliffs/rocks. Look for visual clues such as textured surfaces, smooth pillow-like drifts, or new cornices to help identify wind-loaded features to avoid. Using small test slopes can give you information about how these slabs may be reacting to your weight.

    (3/30/2024)

    A widely breaking slab avalanche on Mount St. Helens. The potential for slabs and dry avalanches increases as you ascend in elevation, particularly on the volcanoes.

    Photo: Clint Lusk

Avalanche Discussion

Preliminary Report: NWAC is saddened to report an avalanche fatality as a result of a cornice fall on Mount St. Helens. On Saturday, March 30, 2024, a snowboarder summited the peak. While standing near the top, he triggered a cornice and fell to his death. Our deepest condolences to the family, friends, and community. 

Discussion:

Sunday's weather should be similar to Saturday in the West South zone. We're anticipating a few more clouds and gustier winds but similar temperatures. We suspect that wet avalanches will be a notch less active than what was seen on Saturday. However, an increase in reactivity and potentially the size is expected by Monday. 

On Saturday, wet loose avalanches were reported from Mount St. Helens, White Pass, Rainier, the Tatoosh Range, and Crystal Mountain. That's pretty much all of our popular observation spots. Slab avalanches were reported on Mount St. Helens, Rainier, and Crystal Mountain - all in high-elevation terrain.

It can be challenging to pinpoint precisely when wet avalanche cycles will peak. Often, we see activity wax and wane during these multi-day warm-ups. Sunday will be another day when the likelihood of dry avalanche problems diminishes, replaced by wet avalanche concerns. Continue to stay vigilant and know that at some point over the next few days, larger and more dangerous avalanches will occur. Cornice collapses, wet slabs, glides, and other shed-style avalanches usually start to peak after a few days of warm and sunny weather.

Most aspects likely contain moist surfaces in some form. Whether they're wet and punchy, a melt-freeze crust, or something in-between, you'll be able to identify the slopes that have the potential for wet avalanches. Under the moist surface, you'll likely find this week's dry storm snow over a prominent melt-freeze crust from our last major warm-up event. This crust is expected to be 1-2 feet down and could make an excellent sliding surface for potential avalanches to run on. We anticipate most avalanche activity to occur above this easily identifiable interface during this event. 

As you head for shadier slopes, drier snow could exist on the surface, particularly at upper elevations. The same melt-freeze crust is lingering a few feet below the surface. A handful of human-triggered avalanches were reported Wednesday-Saturday in this week's storm snow - most of these involved wind-loaded terrain or unsupported features.

Low elevations have less snow than average, and this event may put some into permanent summer mode. Expect shallow coverage, open creeks, and punchy wet snow. In areas where adequate snow coverage exists, wet avalanches could occur.

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