Bulletin d’avalanche

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
Voir sur la carte

Danger d’avalanche

Sat
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
Open full map
Périmé — ce bulletin a expiré 3 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Triggering a 1-2' thick avalanche is possible, especially on slopes that face the sun. You could trigger avalanches remotely—from gentler terrain above, below, and to the sides of steep slopes. Choose lower-angled terrain to reduce your risk. 

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–2.5

    It's possible to trigger wide, 1-2' thick avalanches. They are most likely to fail on crust + facet combinations on slopes that face W-S-E.  Wednesday, riders near Banner Summit remotely triggered a large avalanche from a meadow 50 yds to the side of the slope. The slide broke over 1,000' wide and 2' deep (report). Tuesday, on Mushroom Ridge, SAC staff experienced multiple large collapses and received poor snowpack test scores on slopes with a crust + facet weak layer.

    We're faced with a mid-winter-style snowpack that boasts a complex mix of weak layers. Due to the variable weather in March, the distribution of these weak layers varies greatly from slope to slope and across the zone. Persistent Slab problems are tough to manage. You may or may not see obvious signs of instability on unstable slopes. Multiple skiers or riders might play on a slope before it avalanches. You can reduce your risk by staying off (and out from beneath) slopes steeper than about 35 degrees.

    ADDITIONAL DISCUSSION: While it would take a dose of bad luck, triggering a massive 3-5' thick avalanche on older, deeply buried weak layers can't be completely ruled out. While triggering one of these beasts is far less likely than the slides described above, the consequences would be devastating.

    (3/31/2023) Crown of a very large avalanche that was remotely triggered by riders from at least 500 feet away on the ridgeline above. It broke 4-5 feet deep and 800+ feet wide. This slope faces W at 9,300' in the Frenchman's drainage near Smiley Creek. You can clearly see the two sets of persistent weak layers in our snowpack in this photo. 

Avalanche Discussion

Many sunnier slopes harbor a highly variable mix of facets and crusts in the upper 2' of the snowpack. Some of these slopes have been "cooked" by recent warm temperatures and sun and are no longer an issue. Others, where the effects of warming have done less to help the weak layer heal, remain a concern. Trying to tease out patterns of which slopes remain unstable is tricky at best and dangerous at worst. Wednesday's snowmobile-triggered avalanche (report) came after a day of riding with no obvious signs of instability. 

While most of the snowpack is stuck in winter, the weather finally feels more like spring. With dynamic weather comes a host of secondary avalanche problems to consider:

  1. Wind Slabs: Look for these in exposed terrain (photo). Any wind slabs that you encounter may be perched above weak facets and/or crusts, making avalanches easier to trigger and wider than you'd expect. Wind slabs often form near ridgelines and on the sides of mid-slope terrain features like gullies and ribs. Surface textures like dunes, ripples, or pillows are clues that the wind has been at work. 
  2. Wet Avalanches: Yesterday's warming took the "easy pickings," peeling soft snow from many steep, rocky slopes (photo, photo). Today will be mostly cloudy, and the snow surface will need to overcome a stout crust before becoming wet. While much less of a concern than yesterday, wet snow avalanches are possible this afternoon. Thankfully, this problem is easy to identify. Wet avalanches are unlikely unless the snow you're traveling on gets mushy or feels wet.
  3. Cornices: Large cornices guard the tops of most steep, alpine cirques (photo). Warm temperatures can cause these unpredictable beasts to sag and fail. Limit your time below them and travel far from their edge, where you can easily feel dirt or rocks below your skis or sled. 

Remember, the spring-like weather is only skin deep. Many of us are used to a more uniform, stable snowpack this time of year, one that's seen multiple waves of meltwater followed by a freeze. So far, the abnormally cool and snowy spring has held off this transition, and much of our snowpack is in mid-winter form. Thankfully, we can still safely enjoy some all-time late-season snow conditions by sticking to lower slope angles (less than about 35 degrees), watching for obviously wind-loaded slopes, and avoiding the runouts of large avalanche paths.

Régions couvertes