Bulletin d’avalanche

Turnagain Pass and Girdwood

Chugach National Forest Avalanche Center
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Danger d’avalanche

Thu
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré last year. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Another report of a large human-triggered avalanche on Monday, combined with yesterday's new snow and wind means there are good chances a person could trigger an avalanche up to 3' deep today. This problem can be found anywhere above 1,500' and has proven to be incredibly difficult to predict. With the tricky nature of this weak layer, the only way to avoid being caught in a large avalanche is to stick to slopes that are less than 30 degrees and not connected to anything steeper. Additional hazards today include wind slabs and storm slabs in the upper elevations that could be up to 2' deep. 

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SPECIAL ANNOUNCEMENTS:

Come find us at the Seattle Ridge motorized parking lot on Saturday, March 22 for our annual Turnagain Pass Avalanche Awareness Day! We will be there with Alaska Mining and Diving Supply and the Alaska Avalanche School to chat about avalanches and current conditions and to hang out with the good people of the southcentral Alaska winter community. AMDS will have demo snowmachines, and we’ll be holding down the grill and the fire pit. Stop by anytime from noon until 4:00 p.m. Details Here.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    2–3

    Yesterday's new snow and wind added some stress to the buried surface hoar, but the most impactful thing to discuss is a scary incident that occurred on Monday, March 17. This story has a happy ending and we appreciate this group for sharing. See the video to the right and photos below to illustrate this event. After 30 tracks had been laid on a slope in the Upper Seattle Creek Drainage (Triangle Bowl area), the 31st was a snowboarder who was caught and carried about 1,000 verticle feet in a large avalanche. They attempted to deploy their airbag, but it did not inflate. Thankfully and incredibly, the snowboarder ended up on top of the debris and was able to ride away. Forecasters were in this exact location on Saturday, March 15, where they dug a snowpit about 50' to 100' above the crown of this avalanche and did not find the buried surface hoar. They also dug a snowpit adjacent to this avalanche where they did find the buried surface hoar, but it was not reactive. This situation illustrates how unpredictable and dangerous the weak layer is that we are dealing with.

    We can't trust our snowpits to give us good information and we can't trust the number of tracks already on a slope. Places we thought were safe aren't safe anymore because these avalanches can be triggered from a distance away from the crown and people can get pulled into steeper terrain from low angle terrain. Choose slopes that are less than 30 degrees and do not have terrain traps (any kind of gully feature) below.

    Here's an estimate for how much snow has fallen since Monday:

    • Girdwood: 8"
    • Turnagain Pass: 5"
    • Summit Lake: 2"
    • Seward/Lost Lake: 7"

    Sun effect: Whether the sun is shining through the clouds or out in full force the snow can heat up quickly. Watch for roller balls as indicators things are warming up and a wet loose avalanche could be triggered naturally around some rocks or by a person. These are more likely on south facing slopes and in the lower elevations. 

    Cornices: Yesterday's snow and wind added stress to the cornices that are out there. There are good chances a person could trigger a cornice fall and that cornice fall could trigger a large slab avalanche. Give these looming giants lots of space and watch for them from below.

    Glide Avalanches: Glide avalanches have released within the past week. Continue to avoid spending time underneath glide cracks whenever possible. 

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Strong ridgetop easterly winds yesterday built wind slabs that could be triggered by a person today. There also may be places, especially in the upper elevations that are sheltered from wind, where there is enough new snow (8 to 12") to overload the snowpack causing a storm snow avalanche. These types of avalanches are located in the same place as the more dangerous persistent slab problem so the travel advice is the same as described above. 

     

Régions couvertes