Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Thu
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

Our stormy week will continue on Wednesday, especially on the volcanoes. Recent very large avalanches in the zone should catch your attention and help shape your travel plans. Be prepared for fluctuating freezing levels and increasing avalanche potential throughout the day.

Problemi valanghivi

  • Storm Slabs

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

    None of this week’s storms have been huge snow producers, but they’ve been constant. Expect another one on Wednesday that focuses on the volcanoes again. If you add all these small waves up, there’s been quite a bit of snow this week, resulting in numerous points of failure for you to investigate on Wednesday. Slabs will be thicker and possibly more reactive on the volcanoes or in wind-loaded terrain. Convex slopes, the base of rocks and cliffs, or the leeward side of ridgelines are likely locations where you may encounter sensitive slabs. Use small test slopes and uptrack tests to gauge reactivity. Snowpack tests can help determine weak points. When in doubt, default to slopes less than 35 degrees where triggering an avalanche is less likely. 

    (1/23/2024)

    A large and deep avalanche triggered by explosives at Crystal Mountain. A small wind slab stepped down to this much larger slide. [NE 6600' HS-AE-R3-D2.5-O]

    Photo: Crystal Mountain Pro Patrol

  • Loose Wet

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

    We’ve had close to a week of warm and sometimes wet weather around the West South zone.  At the lowest elevations, there’s likely not a lot of slopes left that haven’t shed their skin during this cycle. However, temperatures have been fluctuating in recent days, so elevations straddling lower and middle are the target area. Temps are expected to rise slightly throughout the day on Wednesday, possibly switching precipitation over to rain for a period of time. This would potentially kick off a new round of wet avalanches. These slides often start at a point and can grow large or trigger slabs as they descend. A newly forming crust on Tuesday night may mean they have a nice sliding surface on Wednesday.

    (1/22/2024)

    Rollerballs and other wet loose avalanche activity. 

    Photo: Dallas Glass

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    The poor snowpack structure around the Solstice Crust persists. This problem won’t give you any direct feedback as you travel. You won’t see shooting cracks or feel collapses. These slides are erratic and unpredictable. They could even fail on slopes that contain multiple sets of tracks. Your best management tool will be to avoid the type of terrain where they are more likely. Big open slopes that are capable of propagating widely and producing a very large avalanche are the areas we’re talking about. 

    (1/22/2024)

    A filled in crown from a deep slab avalanche in Lake Basin near Crystal Mt. E 6500ft. You can still see very large debris piles covered in snow in the basin below. 

    Photo: Dallas Glass

Avalanche Discussion

On Tuesday, it was a warm and wet day for much of the West South zone. Most NWAC weather stations flirted with 32 degrees, many of them reaching the mid to high 30s. The pattern has been similar for much of the last week - high elevation snow and something a bit more moist at lower elevations.

Observations from Tuesday are limited, but Crystal Mountain Pro Patrol reported triggering a D2.5 avalanche in their Southback area during control work using a relatively small trigger. A small wind slab failed and then stepped down to a larger and deeper slab on old layers in the snowpack. The failure layer is not confirmed at this time.

This avalanche occurred a day after our friends at the USGS sent us seismic information about two very large (D4) avalanches on Mount Rainier. They happened on the mornings of 1/21 and 1/22. We have not yet confirmed these avalanches, but the USGS has a good track record. In the same message, they reported an avalanche this week on Mt. Hood. Professionals verified that slide on Tuesday.

This makes three days in a row with a very large, notable avalanche in our zone. Two were naturally occurring, and one was triggered by explosives. Whether these broke on the Solstice Crust or another layer in the snowpack, such as the 1/8 or 1/16, doesn’t really matter when it comes to terrain management. They’re all gigantic, and you should account for this bullseye information when making your travel plans. Talk with your partners about your acceptable level of risk and where you feel comfortable traveling during this relatively warm and wet period.

In areas where the surface was wet on Tuesday, you may find a new surface crust formed by Wednesday morning. This could help stabilize the snowpack for the time being but may also create a nice sliding surface for the fresh snow - whether it's dry or wet.

Regioni coperte