Lawinenlagebericht

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Sawtooth Avalanche Center
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Lawinengefahr

Fri
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 7 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

The danger will rise to CONSIDERABLE as wind speed and snow intensity increase this afternoon and evening. Fresh, sensitive wind drifts will grow in size and extent throughout the day. Underneath these drifts, weak snow buried near the ground continues to pose a threat. To reduce your risk, steer clear of obvious drifts and slopes where the wind has stiffened the snow surface. 

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2

    Yesterday, Ben observed a small natural avalanche in the Sawtooths. Small wind slabs were also reported along Titus Ridge and the Northern Boulders. Expect these slabs to grow in size and extent as snow intensity and wind speed increase throughout the day and overnight. You’re most likely to encounter wind slabs at upper elevation, but strong to extreme wind this afternoon may build sensitive slabs in exposed terrain at lower elevations. 

    These slabs will be most sensitive where they are sitting on firm surfaces, like crusts or older hard slabs. Ripples, dunes, or wave-like patterns can help you identify freshly loaded slopes. Cracks in the snow surface are a sure sign that the slope you’re on is unstable. A shallower wind slab that begins near the surface has the potential to break into deeper weak layers of snow near the ground (see below).

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    2–3

    Ben visited an avalanche that released Sunday in the White Cloud Mtns across the highway from the Sawtooths (photo to right). It broke over 500 feet wide, 4-6 feet deep, and wiped out the majority of the season’s snowpack, covering snowmobile tracks from the previous day. It is unclear if this avalanche failed naturally or was triggered remotely from below. The snowpack isn’t identical in this zone, but similar layers of weak snow exist near the ground. When we talk about unlikely events with high consequences, this is what we’re referring to. 

    What are the common threads in the recent persistent slab avalanche activity?

    • Steep: slopes in prime-time avalanche terrain around 35-45 degrees.
    • Wind-loaded: heavily wind-loaded by recent wind events.
    • Alpine flavor: complex terrain with rock ribs, cliff bands, or minor ridges near the avalanche crowns or flanks.

    The consequences of a triggering a destructive, 2-6 foot thick, persistent slab would be severe. Be aware that even if you aren’t in steep terrain yourself, the snow that you are traveling on may be connected to that sort of terrain above you.

Avalanche Discussion

There are two avalanche problems to contend with today: freshly forming wind slabs at the snow surface and persistent slabs that have the potential to break on weak layers in the lower half of the snowpack. 

Today’s storm will favor our northern mountains where more than a foot of new snow is possible by mid-morning tomorrow. The hazard posed by new snow and wind is relatively straight-forward. Fresh drifts will be sensitive to your weight, and if you’re out today, the snow stinging your face will be a good reminder to keep wind slabs at the top of your mind. It looks like the spike in the avalanche danger will likely occur later this evening as snowfall rates increase and a jet streak bumps up the wind speed from the NW and W. 

Less obvious are the hazards that lurk below. The weight of new-fallen and wind-blown snow will stress weak layers deeper in the snowpack. Over the weekend and earlier this week, these layers proved they weren’t quite ready to go away quietly. Persistent slab avalanches were observed in the White Clouds, the Boulders, and the Pioneer Mountains. Similar avalanches are possible again today, particularly in areas where storm snow overloads a shallow weak snowpack.

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