Avalanche forecast

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
View on map

Avalanche danger

Mon
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
Open full map
Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Triggering a large, 1-2 foot thick slab avalanche that fails on weak snow near the ground is today's primary avalanche concern. Such slides are most likely on wind-affected slopes at upper elevations and on shaded middle elevation slopes (those facing E-N-W). You aren't likely to observe obvious signs of instability before triggering such an avalanche, and slides can be triggered after many skiers and riders have crossed a slope.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Weak snow at the base of the snowpack is the source of the primary avalanche concern. A 1-2 foot thick slab of snow rests uncomfortably on top of this weak snow. This combination of slab + weak layer exists on many upper elevation slopes and on shaded middle elevation slopes (those facing E-N-W). If you dig down on shaded slopes you'll find an obvious layer of very weak snow near the ground. On slopes that face the sun you'll find a less-obvious layer of small facets on top of a stout melt-freeze crust.

    As the days tick by without significant loading, obvious signs of instability decrease. Reports of large collapses have become much less frequent and the most recently observed large avalanche failed 3 weeks ago. The likelihood of triggering one of these slides is decreasing, but not going away. Tracks on a slope are not an indication that the slope is stable — avalanches may be triggered after many riders have crossed a slope. 

    You can eliminate your risk of encountering one of these large slides by steering clear of avalanche terrain harboring this combination of slab + weak snow. If you are planning to enter avalanche terrain, spend a bit of time thinking about the consequences of triggering a slide. Slopes with terrain traps at the bottom and with trees and rocks that you can get dragged through amplify the consequences of triggering an avalanche. Read more about this in the Forecast Discussion section below. 

Avalanche Discussion

DISQUIETING STABILITY

Our snowpack trends towards what I think of as a "disquieting stability." This zone has picked up just 3-9 inches of snow in the past three weeks. The most recent large, slab avalanche that failed on the weak snow at the base of the snowpack occurred 22 days ago on December 9th (photo here). During this prolonged period of dry weather, stability has gradually improved and the likelihood of triggering avalanches has gradually decreased. Decreased, not disappeared. 

The slab overlying our basal weak layer is 12-24 inches thick here. In areas where the snowpack is thinner, much of this slab is losing strength and faceting away. In areas where it is thicker and is maintaining its structural integrity, triggering a large slab avalanche remains a disconcerting possibility. You are most likely to trigger avalanches in recently wind-loaded terrain where wind slabs are adding stress to the weak snow at the base of the snowpack and adding some "meatiness" to the overlying slab. 

As stability improves and we choose to selectively enter avalanche terrain, I encourage you to be careful and diligent with that process. Take the time to think about whether our weak layer of concern exists on the slope you are hoping to ski. If it does, and if the overlying slab is dense enough to keep you from skiing right through it to the ground, the possibility of triggering a large slab avalanche is on the table. Has the slope been recently wind-loaded? If yes, this increases the likelihood of triggering a slide. Does the slope end in a gentle transition or is there a nasty terrain trap at the bottom that amplifies the consequences of being caught in a slide? Is the slope free of rocks and trees or will you get thrown downhill through a sea of objects much tougher than you are if you get caught and carried? Spending the time to think about these things helps us to minimize the risk of having a bad outcome today. Remember that this process is an ongoing one. When you decide to move to a new slope or you go to an area where you haven't been this season take the time to work through these questions again.

In addition to the primary persistent slab concern, it's also worth thinking about smaller loose snow avalanches today. The surface snow on shaded slopes has become so weak that it is ready to just fall down the hill in a type of dry loose avalanche known unofficially as a "facet-lanche". I triggered just such a small slide on Friday above Smiley Creek and a public observer reported triggering a similar but larger slide near Titus Ridge on Thursday. Though they aren't likely to be large enough to bury you, these slides can pack a punch and take you for a ride through unpleasant terrain. 

Check out our latest Weekend Update from Brooke to get caught up on what has been happening this week with our snowpack.

Regions covered