Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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Rising freezing levels, heavy precipitation, and strong winds will result in dangerous avalanche conditions on Friday. Choose simple terrain that minimizes your exposure to slopes over 35 degrees, where triggering an avalanche is more likely. Storm totals will be significant on the volcanoes, and we may approach HIGH avalanche danger.

Problemi valanghivi

  • Storm Slabs

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

    Friday will be similar to Thursday, but warmer and with more snowfall. Look for unstable slabs on slopes over 35 degrees, particularly if they're convex or wind-loaded. The main event should occur Thursday night, so the reactivity of storm slabs may be greatest first thing in the morning. This could also be when you observe more natural avalanche activity. Since we're on a warming trend, heavier snow will likely overlay softer snow, creating an upside-down snowpack. In some locations, thin melt-freeze crusts could exist below the recent snow, making for a good bed surface. Slabs will be larger on the volcanoes or as you ascend in elevation where wind-loading is more common. You can use small test slopes, hand pits, or uptrack tests to gauge the slab potential of the new snow. If blocks fail easily in your tests, or you see shooting cracks during your travels, choose simpler or more treed terrain where the consequences of a slab avalanche could be less. 

    On the volcanoes, more significant snowfall means thicker slabs and a higher likelihood of natural activity. You may want to consider avoiding all avalanche terrain until this storm has run its course in these areas.

    (3/19/2025)

    A slab avalanche in a clearing in the trees. This one is deep and broke on a steep, unsupported slope. 

    Photo: Josh Lipkowitz

Avalanche Discussion

Miracle March rages on in the West South zone. After a relatively stormy Thursday that saw 6-10" of new snow, moderate to strong winds, and slowly rising temperatures impact the zone, a more potent, wetter, and warmer storm will roll through Thursday night into Friday. Since this storm will be warmer, we expect a changeover to rain at lower elevations. Most impacted areas should be below our forecast zone, but don't be surprised to see wet avalanche activity anywhere the snow surface is moist, and you are sinking in past your ankle.

As the storm peaks overnight, we anticipate natural avalanche activity, particularly in favored locations such as the volcanoes. Although naturals could occur during the day, we don't believe they will be widespread. If they're going to happen, it will likely be during or shortly after periods of intense loading by precipitation or wind, such as in the morning hours. Be especially leery on the volcanoes.

This past week, storms have delivered several feet of new snow, strong winds, and plenty of avalanche activity. We do not have any identified layers of concern in the upper snowpack above the atmospheric river (AR) crust, but plenty of interfaces are still visible if you dig. On Thursday, NWAC forecasters near Crystal Mountain noted that numerous interfaces were highlighted in formalized snowpack tests but did not show much propagation. Recently formed wind slabs were reactive in recent days but should be on the mend in the warmer weather. However, those that aren't fully healed are now buried below new snow, making them harder to assess. Many of this week's avalanches have failed on wind-loaded features, and we suspect if you get a deeper release on Friday, it will be in a similar location. Overall, the upper snowpack over the AR crust varies in depth based on aspect and elevation. The same goes for the number of crusts formed on sunny days. The result? Not all slopes will act the same, even if they seem similar.

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