Bollettino valanghe

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

Wed
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

The combination of strong winds and new snow is building a batch of small wind drifts and slabs in terrain exposed to the wind. Though small, these slabs may be able to knock you off your feet and send you downslope, entraining plenty of weak, sugary snow along the way. Avalanches may break wider than you might expect, thanks to the weak snow underneath the new snow. 

Conditions are most dangerous in the western portion of this zone, from Dollarhide Summit west to the Soldier Mountains.

Problemi valanghivi

  • Wind Slabs

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

    This storm is bringing much more wind than snow to this zone. Strong to extreme winds have been blowing off and on for the past 30 hours. These winds are finding what little loose snow there is and building small, hard slabs. This process will continue this morning after snowfall draws to a close. Though not large enough to bury you, these slabs can knock you off your feet and send you downslope. Consider the consequences of being swept off your feet and carried through the terrain you are in. Small slabs can carry high consequences if they drag you through trees or over rock bands. Look for stiff, hard drifts near ridgelines and along mid-slope features like gullies and ribs that slow the wind down. Winds have been blowing hard enough that I expect you'll be able to find these small slabs at all elevations, particularly in the western portion of the zone, where more snow is falling and the winds are stronger.

    In areas sheltered from the wind, thick stacks of very weak facets developed during the drought of the past month. Triggering a loose snow avalanche involving these weak facets is a possibility on shaded slopes approaching about 40 degrees. Warm temperatures and sunshine produced some small wet loose avalanche activity yesterday at low elevations on slopes that face the sun. Today's cold front should prevent wet snow issues from arising today, but if you're finding wet snow at the surface you should be thinking about wet loose snow.

    ADDITIONAL DISCUSSION: On the western side of this zone (Dollarhide and west to the Soldiers), weak layers are buried in the upper 1-2 feet of the snowpack. These layers have largely become unreactive, thanks to an extended period without significant loading. If you are unlucky enough to find the "sweet spot" where these layers remain reactive you'll almost certainly be in rocky, wind-affected terrain steeper than about 35 degrees where recent drifting has added weight to these layers. These layers appear to be worst on slopes that directly face the sun where crusts+facets are buried.

Avalanche Discussion

The snowpack varies significantly across this zone. Snowfall in January and February favored the western side of the zone (Dollarhide to the Soldiers) and the snowpack is deeper here. Weak layers buried in the snowpack are sitting underneath dense slabs of snow. These layers have trended towards dormancy thanks to a lack of loading. In the mountains above the Wood River Valley, snowfall has been essentially nonexistent over the past 6 weeks. Here, you'll find a very weak snowpack composed almost entirely of faceted snow. Here's a look at the range of problems you might expect in this zone:

Wind slabs: The combination of fresh snow and strong winds is building sensitive wind slabs. Strong winds build slabs in unusual locations. I expect to see slabs at most elevations, though these will be largest and most reactive in exposed middle and upper elevation terrain. Slabs may be building even at lower elevations. These are likely to be smaller and your biggest concern with them involves being pushed into terrain traps like creek bottoms and dense trees. Typical locations for low elevation wind slabs in this zone are at the mouths of major drainages above the Wood River Valley and in the foothills above Fairfield. Slabs are building on a variety of weak snow surfaces that developed over the past weeks. Avalanches that fail on these weak layers will break wider and may be more sensitive than you might expect a "simple" wind slab to be.

Loose snow: If you are finding soft, sheltered snow in very steep terrain (approaching 40 degrees) you'll be able to trigger loose snow avalanches today. These will involve both the new snow and the weak, faceted snow described above. Warm temperatures and sunshine produced some small wet loose avalanche activity yesterday at low elevations on slopes that face the sun. Today's cold front should keep things cooler than yesterday, but if you're playing on slopes that face the sun and finding moist/wet snow you'll be well served to think about triggering a small wet loose avalanche.

On the western side of this zone (Dollarhide Summit and west to the Soldiers) you'll find some ugly weak snow sitting underneath very dense slabs. Triggering a large involving this snow is unlikely, but the outside possibility continues to keep my hackles up. Fortunately, avoiding this problem is fairly straightforward. You can dramatically reduce your risk of triggering a large avalanche today by avoiding rocky, wind-affected alpine terrain steeper than about 35 degrees. 

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