Bulletin d’avalanche

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
Voir sur la carte

Danger d’avalanche

Sat
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
Open full map
Périmé — ce bulletin a expiré 6 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

You're most likely to trigger a large, 2-3 foot thick avalanche on steep, wind-drifted slopes. These slides are also possible in terrain more sheltered from the wind. Avalanches may be triggered remotely—from below, above, and to the sides of steep slopes. 

Problèmes avalancheux

  • Persistent Slabs

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

    Observations of unstable snowpack tests and collapsing were reported on each of the last two days near Galena Summit. The culprit? A weak layer of facets buried in mid-December. Although we're over a week out from receiving snowfall, this problem won't go quietly. The exceptional nature of this weak layer keeps the odds of triggering a slab avalanche elevated for several days following a storm. 

    Near Galena Summit on Saturday, skiers remotely triggered a 1.5-2' deep avalanche from low angled terrain (more details, video here). On Sunday in the Pole Creek drainage, a group of riders remotely triggered an avalanche that buried the road they were riding on. This happened after the 4th rider had passed underneath the start zone above.  The snowpack in the southern part of this zone is very similar to where these avalanches occurred (see Chris' video below/to right).

    These slides are most likely where:

    • The wind has formed drifts or stiffened the snow surface. Watch for dunes, waves, or ripples on the snow surface to identify these areas.
    • On or below slopes over about 35 degrees. 

    The best way to reduce your risk is by sticking to lower-angled terrain and steering clear of slopes with runout zones that have trees, rocks, or terrain traps. Given the possibility of remote-triggering slides, avoid slopes directly beneath avalanche start zones. 

Avalanche Discussion

Just about everywhere we look we see avalanches that failed during our last storm. In the last few days, we've observed avalanches in the southern tip of the Smokys (in the Soldier and Wood River Valley Zone) and in 4th of July Creek in the White Clouds.

In all corners of the forecast area (that hold enough snow), it's the same story; weak facets buried in mid-December.  The variable, and what's at the root of different problems and danger levels between zones is the thickness of the slab.

Banner Summit "Low Probability, High Consequence"This zone has the deepest snow. The Banner Summit Snotel station shows a snow depth of 4' at just 7,100' of elevation. In this area, the December facets are buried under 3' of heavy snow. The dense slab is "protecting" the weak layer, making it more difficult for skiers and riders to trigger slides. However, the outcome of triggering one of these beasts is grim at best. 

Sawtooths & Western Smoky Mountains, Galena Summit & Eastern Mountains "The Sweet Spot"With less snowfall than Banner Summit, these two zones have a snowpack structure that remains ripe for human-triggered avalanches. The slab over the December facets is about 1.5-3' thick. Thin enough in many areas to be likely to trigger, but thick enough to produce large and dangerous avalanches. 

Soldier & Wood River Valley Mountains "A Fine Line"This zone shows large variability in snow cover and problem distribution. Snow depth in the Soldiers sits at about 3', Dollarhide Summit in the Smokys is pushing 4', and Baldy along with many of the mountainous areas to the east of the Wood River Valley hover around 2'. This video from Croy Canyon on Tuesday shows a weak but generally stable snowpack that lacks a slab. Contrast that with this video of a healthier slab, poor snowpack structure, and unstable snowpack test scores from near Dollarhide Summit yesterday. 

Wherever you travel, it's important to keep the big picture in mind. At any location where you're finding snow deep enough to ride or ski, you'll find a slightly different flavor of this same problem. The most effective way to deal with this poor snowpack structure is to stick to lower angled, low consequence terrain. Before committing to a slope, look for terrain traps like cliffs, trees, and gullies that will increase the consequences of being caught. Don't let your guard down. This uniquely well-developed and widespread weak layer should be at the front of your mind.  

Régions couvertes