Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
Vedi sulla mappa

Pericolo valanghe

Sun
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
Open full map
Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

We are entering a pattern of freeze thaw, with more thaw than freeze. Each day we could see large wet avalanches in isolated, steep terrain. Get off of steep slopes if you begin punching into deep, wet snow. 

Problemi valanghivi

  • Loose Wet

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

    Avalanches will become possible on very steep slopes with daytime warming. Look for wet snow surfaces once surface crusts break down by the afternoon. Once you begin punching into wet snow, then it's time to move off from steep slopes. If you find a thick crust topping snow surfaces, then avalanches are unlikely.

    On steep, low elevation slopes avalanches have been running on the ground. These are scary because they've been taking the entire seasons worth of snowpack with it. Stay out from under large steep slopes if there is no surface crust.  Don't linger or stop in runout zones and creek beds where avalanches could drain into.  

    (1/13/2022) Large wet avalanche off of Icicle Ridge. Likely occurred on 1/12/2022 or 1/13/2022

    Photo: Katie Warren

  • Wet Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    2–3

    With multiple nights of above freezing temperatures and free water in the weak snowpack, the potential for deeper wet slab avalanches remain. Water pooling on crusts or weak layers within the snowpack could initiate very large avalanches. Wet, deep and punchy snow can signal danger for this type of avalanche.

    While many large terrain features previously slid during recent storms, there may be slopes with lingering deep instabilities. We believe these are unlikely, however, the consequences of being caught in or underneath one would probably be unsurvivable. With plenty of uncertainty surrounding this problem and the destructive nature of these avalanches, don't linger underneath large, complex terrain. This problem may linger until we get a solid freeze, or free water and warmer temperatures has a chance to transform the weaker snow grains into sintered, bonded grains. 

    (1/6/2022)

    A snow profile at 3000' at Snoqualmie Pass. Note the pooling water well below the surface. This could result in wet slab avalanches. 

    Photo: Alyssa Young

Avalanche Discussion

Over the last three days, most weather stations have sustained above freezing temperatures, and an avalanche professional at Mission Ridge saw moist snow grains to the ground. Large avalanches have occurred as recently as Thursday in the mountains surrounding Leavenworth. This weather pattern is not our typical situation where we get a deep freeze after substantial snow and rain. The sustained warm temperatures will mean the snowpack will be slower to stabilize, and water will continue to slowly move through the snow and pool on crusts and weak layers. On Wednesday and Thursday, NWAC forecasters observed large avalanches off Wedge Mountain and Icicle Ridge in Leavenworth.  Natural wet loose avalanches blocked Highway 2 in Tumwater Canyon on Thursday. It will be essential to assess snow conditions as you enter new terrain over the next few days. 

Before and during this storm, large and very large avalanches ran naturally and were triggered by explosives on various deeply buried weak layers. The more recent layers consisted of large stellars, facets, and surface hoar from 1/2 and 12/29. A decomposing crust from the Solstice was the bed surface for some slides at Mission Ridge. An even deeper crust from Early December showed propagation potential on high elevation, shaded slopes in the Icicle drainage. These layers are likely buried 3 to 8ft deep and could still be capable of producing avalanches.

Regioni coperte