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

Wind loaded terrain continues to be the most likely location for triggering an avalanche. Larger and more deadly avalanches are possible due to weak layers buried deeply in the snowpack. Conditions may not be what you’re used to, so dial back your terrain choices.

Problemi valanghivi

  • Persistent Slabs

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

    At this point, we have fairly good confidence that a weak snowpack structure exists throughout the zone and that in most areas, the main layer in question is about 3 feet down. You may not experience signs of instability as you travel due to the depth at which these layers are buried. However, you need to know that a weak snowpack structure exists, has been the source of many recent avalanches, and is not healing or going away anytime soon. Even if you believe the likelihood of triggering may be decreasing due to its burial depth, the consequences remain sky-high.  We have some uncertainty about what it would take to trigger one of these slides at this point, but it could be a step down from another avalanche, a snowmobile, cornice, or even just a shallower spot in the snowpack. We believe that the most likely places for these slides to run are open terrain features and start zones over 30 degrees. Any avalanche triggered on these weak layers will most likely be large enough to be fatal.

    (2/9/2021) This widely breaking slab was observed at Paradise on Monday (2/9). [6500' E aspect. Photo: Porter Michaels]

  • Wind Slabs

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

    Observations from Paradise on Monday showed that snow is easily being transported by the wind. Look for Wind Slabs to continue to develop on leeward slopes near ridgelines, or near rocky terrain such as cliffs and gullies. Convex rollovers or slopes over 35 degrees should be more prone to triggering avalanches, whether they are wind-loaded or not. As you travel, you can use uptrack tests or test slopes to see how the recent snow is reacting to your weight. Look for visual clues such as textured snow surfaces, freshly built cornices, or smooth pillow-like piles of snow to help you identify where the wind has affected the snow. Avoid any slope greater than 35 degrees that you suspect is wind-loaded.

    (2/9/2021) Plenty of evidence of Wind Transport at Paradise on Monday (2/9). You can look for blowing snow to help you identify Wind Slab potential. [Photo: Porter Michaels]

Avalanche Discussion

We continue to get reports of recent avalanches in the West South, even as we distance ourselves from this past weekend’s storm. With cold temperatures, it often takes the snowpack longer to heal than you may be used to. With persistent weak layers, that timeframe is extended even further. These layers do not heal quickly and are not going away anytime soon. We have had a lot of large and dangerous avalanches in the West South this past week, and observations by professionals and recreationalists alike continue to confirm the existence of a weak snowpack setup. You need to keep approaching terrain with caution and being suspicious of open terrain features greater than 30 degrees. There were multiple avalanche involvements and close calls this past weekend, which culminated in a fatality on Monday in the East Central zone. The snowpack at the accident site was found to be a similar setup to what has caused all of the recent avalanches in the West South. The crown depth measured 4-5 feet and the bed surface was the Mid-January crust. With wind loading and such a vast zone, we can’t rule out similar slab depths here in the West South, and we certainly have the crust/facet combo. Stay safe out there and let us know what you’re finding.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

Regioni coperte