Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Tue
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
3 · Marcato
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In sintesi

6:20a Update: Very dangerous avalanche conditions are developing. Storm slab instability may last longer than expected and slides may remain easy to trigger through the day on Monday. Stay off of and out from underneath steep slopes if you find shooting cracks and recent avalanches.

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    1.5–2.5

    Large to very large natural avalanches are possible overnight on Sunday, and may continue into Monday. Instability may persist longer than normal because the old/new interface is very weak in many areas. Slabs may react in surprising ways, and could be initiated from a distance, from the sides of steeper slopes, or beneath them. Open pockets in the trees could produce unsuspecting avalanches. Slides should be larger and deeper at higher elevations, where wind has created thicker slabs over the past few days. 

    Watch your slope angles, stay off slopes steeper than 30 degrees and well away from large, steep features. Look for signs of instability such as recent slab avalanches,  shooting cracks, and whumphing collapses. 

    Example storm slab from last week.

    Photo: Stephen Semanski

Avalanche Discussion

A big change is coming with this next storm, and it's time to adjust our mindset from the relatively good stability we've enjoyed in recent days. Winds ramped up on Sunday, likely creating thick slabs in many areas. Observers had noted large surface hoar laying flat on many aspects and on both sides of the Hairpin Valley, at least. Suncrusts were reported from steeper S-SW facing slopes above Highway 20. The take away-Recent temperatures have likely created widespread weak and faceted surfaces (see video below for an example from the East Central zone). 

Several small natural wind slab avalanches were reported throughout the week, including Saturday, as moderate ridgeline winds easily moved low-density snow and formed shallow wind slabs below ridgelines.  Small loose dry avalanches or sluffs were easy to find in steep wind-sheltered terrain. 

At the interface that was buried around the solstice, observers reported finding surface hoar as well as a thin sun crust on steeper S-SW slopes.  While no recent avalanche activity has been observed down to these layers in this zone yet, further west in the Mt Baker backcountry, a deep persistent slab up to 5' deep released sometime on 12/31 on surface hoar buried above the solstice crust.  Other avalanches down to this interface have released infrequently over the past week on the west side of the Cascades. Keep this in mind as we move into this next week with stronger storms on the way. 

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