Bulletin d’avalanche

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Danger d’avalanche

Sun
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

You're more likely to trigger an avalanche on wind-loaded slopes, but it's also possible in steep, wind-sheltered terrain. Avoid obvious large drifts or slabs and choose lower-angled terrain to reduce your risk.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1.5–2.5

    A snowmobiler triggered this slab avalanche yesterday (photo). We don't have much information yet, but it appears to fit the pattern of the several skier and rider-triggered slides of the past week. Many of these slides appeared to fail on a thin layer of surface hoar. Recent avalanche activity is focused on NW-N-NE aspects between 8000-10,000' in elevation (view graphic). Sunnier slopes that lack surface hoar may harbor a weak layer of facets and/or crusts. JP found this setup Thursday in the Headwaters of the Salmon River (photo). 

    There are also more deeply buried weak layers to keep on your radar. Facets (often found near crusts) exist in the middle of the snowpack (photo) and larger facets sit near the base of the snowpack (photo).  Snowpack depths in this zone are highly variable. Triggering an avalanche on these deeper layers can't be ruled out in steep, rocky, wind-affected terrain or in drier portions of the zone where snow cover is thin.

    Persistent slab avalanches are tricky. These avalanches may break wider than expected or higher on the slope above you. You may be able to trigger avalanches remotely—from gentler terrain below, above, and to the sides of steep slopes.  You can significantly reduce your risk by steering clear of steep, wind-affected terrain. 

    (1/15/2023) This avalanche was triggered by motorized users in Pole Creek, probably on January 14th. It likely failed on a persistent weak layer buried in the first week of January. 9200', N.

Avalanche Discussion

Snowpack characteristics vary widely across this zone. Some areas have a deep, mostly strong snowpack. However, if you head out into the White Clouds, southern Boulders, or the Pioneers, you're more likely to find a relatively shallow, wind-affected snowpack that's primarily weak and faceted. Lately, buried surface hoar has grabbed our attention, and rightfully so. This tricky weak layer produced numerous avalanches over the last week including skier and rider-triggered slides near Galena Pass and Pole Ck in the southern White Clouds. As this more obvious near-surface instability slowly heals, it's important that we don't forget what we're left with.

Prominent weak snow layers were buried in December the worst of which was a crust + facet combination that produced this large avalanche on New Year's Eve near Galena Pass (report). These layers continue to produce poor snowpack test scores (Dollarhide, Baker Ck, Trail Ck). And who can forget the widespread weak layer of facets and depth hoar at the base of the snowpack? Just about all slopes harbor this snow. The most recent slides involving this weak layer were triggered in late December near 4th of July Pk (report) and Baker Lake (report). Each of these last two slides share a common trait—they were triggered where the snowpack was thin. 

As a local professional recently stated, "Although [we're] starting to step out... [it's] far from open season." I haven't heard of anyone center-punching wind-affected alpine bowls this season... and there's a reason for that. Persistent weak layers can take weeks and even months to stabilize. While the peak of the near-surface weak layer instability has come and gone, we're simply slowly returning to a well-established complicated baseline. One that's defined by the distinct possibility of triggering a large avalanche on a deeper weak layer. 

Don't miss out latest Weekend Update! Tune in as Chris recaps the weather and avalanches of the last week and gives us a look at what to expect this weekend (here).

Régions couvertes