Bollettino valanghe

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

Sun
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

You could trigger avalanches large enough to bury you on slopes with old snow at the base of the snowpack (upper elevations and on shaded middle-elevation slopes facing W-N-E). Avalanches can be triggered by the first, third, or tenth rider on a slope, and may break well above you. Look for small pockets of unstable, wind-drifted snow in exposed terrain.

Problemi valanghivi

  • Persistent Slabs

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

    Weak snow from November forms the base of the snowpack on many slopes. You can trigger avalanches involving 1-2 foot thick slabs that fail on this weak snow. You'll find this unstable combination on all upper elevation slopes and on middle elevation slopes that face away from the sun (W-N-E). On shaded slopes you'll find a thick stack of facets underneath this slab. On slopes that face the sun, you'll find a less obvious layer of facets on top of a crust. 

    As days pass without loading, obvious signs of instability such as collapsing of the snowpack have decreased. Don't interpret this as an indication that the problem has gone away. The first sign of instability involving this weak snow may be the large slab avalanche that you trigger. Tracks on a slope are not indicators of stability — avalanches can be triggered by the first, third, or tenth rider on a slope, and may break well above you.

    ADDITIONAL DISCUSSION:  2-4 inches of snow fell here overnight. Expect to see this snow sluffing easily and running downslope quickly on the stiffer snow underneath. You'll be able to trigger these sluffs in steep terrain, and they will occur naturally under the influence of today's sunshine.  In areas exposed to the wind, you'll find isolated pockets of unstable wind slabs that may be easy to trigger, thanks to the weak snow surface they were deposited on. While neither of these issues is likely to produce large avalanches on their own, small slides traveling downslope can be effective triggers for deeper weak layers. 

Avalanche Discussion

FRAMING YOUR DAY

You'll be pleased to find a return of winter flavor when you head into the backcountry today. Temperatures will be 20 degrees F cooler than in recent days and you'll be moving through the 2-5" of new snow that fell here overnight. This refresh will significantly improve skiing conditions and help keep your sled cool on the way in. Unfortunately, this new snow is just lipstick on the pig of our persistent slab problem.

The snowpack has been relatively simple thus far. It isn't pretty, but it is fairly straightforward. A layer of weak, early-season snow rests uncomfortably under dense, 1-2.5 foot thick slabs of snow on many slopes. Today's new snow is adding some complexity and some extra stress to this weak snow, particularly in areas where the wind is building fresh slabs.

Pay attention to the minor issues you may encounter from the new snow — loose snow avalanches and wind slabs, both of which may run fast and far thanks to the stiff surfaces underneath. But don't lose your focus.  The persistent slab problem should continue to drive your travel choices today. The same terrain that we've been worried about all season is still worth worrying about today. If you head into areas where weak, November snow exists at the base of the snowpack you will choose to enter a dangerous lottery. The odds of losing this lottery (triggering a large slab avalanche) remain uncomfortably high. 

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