Bollettino valanghe

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

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2 · Moderato
Limite del bosco
1 · Debole
Sotto il limite
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In sintesi

You may be able to trigger avalanches up to 2 feet thick where the wind has drifted snow. Loose snow avalanches may release on very steep slopes receiving prolonged direct sun. 

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    The sun may initiate loose snow avalanches on very steep slopes. Variable cloud cover will likely mute this problem in many areas, but it can arise quickly in direct sun. These slides commonly initiate near warm rocks, fanning out and collecting snow as they go. Although likely to be small, these slides can travel quickly on the slick surfaces beneath them. Pay attention to the terrain above you. Large slopes can produce slides big enough to knock you off of your feet and carry you places you don't want to go. 

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    Expect to find thin, fresh wind slabs in the alpine. Yesterday in the northern Boulders, skiers observed active wind-loading and experienced collapsing in multiple small wind slabs. Wednesday in the Smoky Mountains, I found small wind slabs up to 1' thick (photo). Similar drifts were reported south of Smiley Ck (photo). 

    Wind slabs often form near or just below ridgelines, on the sides of cross-loaded chutes, or on aprons below steep cliffs. Many of them rest on slick crusts. This means they may be easy to trigger, break wider than expected, and will pick up speed quickly as they travel downslope. 

    Pay attention to how the snow feels under your skis or boards. If the snow surface suddenly stiffens or becomes more supportable, you've found a wind slab. Cracks shooting out in front of your skis or boards are a red flag warning you to be cautious. Surface clues like dunes or ripples can tell you the wind has been at work.  

    ADDITIONAL DISCUSSIONWeak layers consisting of crusts, facets, and surface hoar, exist in the upper part of the snowpack. The weakest snow we've seen is on the shady half of the compass, spanning upper and middle elevation terrain (photo). A persistent slab occurred last week after a small storm near Galena Summit (photos and details here). Choose more conservative terrain on shadier slopes as you climb in elevation, particularly where the wind has stiffened the snow surface or formed drifts.

    (3/9/2022) This small wind slab formed just below an exposed ridge on an E-facing slope at 9,600' in the Smoky Mountains. These small slabs ranged from 15-25 cm thick in this location and tapered quickly in more sheltered terrain.

Avalanche Discussion

In our northern zones, we've buried a complex mix of weak snow layers including multiple crusts, layers of facets, and occasionally surface hoar. The worst of these layers exist on shadier (NW-N-NE-E) at middle and upper elevations. The composition of these layers is highly variable and depend on aspect, elevation, slope angle, and the amount of recent snowfall. 

As a quick example, you can see the contrast between this S-facing pit and this N-facing pit I dug on Wednesday in the Smokys. These pits were less than a 1/4 mile from each other and at similar elevations. The point here is that it's complex. Not only do the weak layers change, but the thickness and stiffness of the slab vary as well. In some areas, you'll be scratching around in "dust on crust". Around the corner, you could run into a stiffer, sensitive drift.

New snow and continued wind-drifting over the last few days formed a fresh batch of wind slabs in alpine terrain. These slabs may be sensitive on their own, even without a persistent weak layer below them. More sinister, however, is where they rest atop the weak layers described above. The complex distribution and sensitivity of these layers make it hard to know if the slab you encounter will be your average small wind slab that's easy to manage, or one that breaks above you and wider than expected. With increased complexity comes increased uncertainty. The best way to deal with the uncertainty is to dial back your terrain choices. Personally, I'm not willing to trust a steep, shaded slope with an obviously stiffer slab near the surface. 

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