Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

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

In sintesi

A near-constant trickle of very large avalanches, ongoing mild and wet weather, and a well-known deep weak layer in the snowpack combine to make conditions dangerous. In this case, it’s more about the complexity and consequences than the likelihood of any avalanche. Look for simple and smaller avalanche terrain to help reduce your risk.

Problemi valanghivi

  • Storm Slabs

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

    Several days of precipitation with oscillating temperatures and periods of sun formed a variety of layers in the upper snowpack. You’re most likely to trigger shallow slabs in the last 24hrs or so of snow. However, in some spots, avalanches could break slightly deeper, particularly when crust from sun or rain formed within the new snow. This could cause things to act differently by aspect and elevation. Use lots of small slopes and hand pits to highlight potential weak layers. 

    The mild temperatures should help the new snow heal quickly. Often, avalanches become more localized to features like convex rollovers, very steep slopes, unsupported areas, wind-loaded pockets, and the base of cliffs.

    (1/19/2024)

    Two natural storm slabs from earlier in this storm cycle. 

    Photo: White Pass Ski Patrol

  • Loose Wet

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

    Near and below the rain-snow line, things will be messy. Wet, heavy, sticky snow could flow downhill more like a river of concrete. These avalanches seem easier to manage but don’t let them catch you. If they do, they can take you wherever they want to go. This could include over a cliff or into a creek. 

    If you find wet, sticky snow deeper than your ankle, use a bit of extra caution and seek out lower angle and less consequence terrain. 

    (1/22/2024)

    A small wet loose "push-o-lanche" on east peak at lower elevations. 

    Photo: Dallas Glass

  • Deep Persistent Slabs

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

    We’ve been forecasting persistent slabs for two weeks now. That’s a long time for the PNW. However, near-daily reports of very large slides emphasize this problem hasn’t gone away. Just this week, we’ve heard reports of at least 3 very large avalanches on Mt Rainier and near Crystal. 

    This isn’t a problem that will “talk to you” or that you can easily see. The only real way is to dig snow profiles. However, the recent avalanches are the most compelling evidence. Give large avalanche start zones a wide berth and limit any time you spend in the track or runouts of bigger slide paths. Discipline and patience are key in waiting out this dangerous avalanche issue.

    (1/24/2024)

    You can see the crown from the initial wind slab in the upper left, that then triggered this deep slab avalanche. 

    Photo: Crystal Mt Ski Patrol

Avalanche Discussion

If you take any one avalanche problem by itself, Thursday might not be that big of a deal, but combined, it’s hard not to call it dangerous. The complexity and consequences deserve a higher level of caution than normal. The mild wet weather isn’t helping. Again, no single day is that big, but it’s enough to keep the danger elevated. 

Storm totals since 12/20 range from 12-20 inches around the zone. Crusts within and at the base of this snow are present in some locations and at certain elevations. This makes the upper snowpack a bit harder to summarize than normal. 

Deeper in the snow, we’re continuing to watch several layers with facets and crusts (1/ 8, 12/30, and Solstice) It’s hard to say which layer many of these big slides failed on, but at the end of the day, they are all big, deep, and scary. On Tuesday, an explosive-triggered wind slab at Crystal Mt stepped down into older snow failing on a layer of facets and breaking widely. This very large slide joins a pair of seismically detected avalanches from the USGS on Mt Rainier earlier this week.

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