Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Fri
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

Dangerous avalanche conditions will continue with more new snow and wind on Wednesday night. Avalanches may be easy to trigger on steep slopes where you find up to 2 feet of recent snow, and especially where the wind forms drifts below cliffs and ridges. Avoid being on or under extensive, steep avalanche paths at middle and upper elevations.

Problemi valanghivi

  • Storm Slabs

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

    You're most likely to trigger avalanches in the recent layers of snow near the surface or where the wind has formed deeper, stiff slabs. Avalanches in wind-drifted slabs could be dangerously large and could involve much deeper weak layers. If enough sun gets through the clouds, avalanches could become easy to trigger on southern aspects.

    Take time to test the new snow on inconsequential slopes before traveling in terrain steeper than 35 degrees. Stay off of and well out-from-under steep start zones in wind-loaded terrain, leeward sides of ridges, and all at upper elevations. If slides break to deeper layers they could be 3 feet deep, break widely and could run long distances downhill. 

    (12/20/2021)

    Example storm slab avalanche on a small slope.

    Photo: Adam Butterfield

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–3

    Last weekend, strong winds created stiffer slabs that now overly a layer of faceted grains, surface hoar and crusts. Heavy new snow and strong winds may be enough to create avalanches that run on these layers.  

    Stay off of and out from underneath steep slopes at upper elevations. Avalanches may propagate widely and run full path to lower elevations in some areas.  Choose smaller, well-supported slopes and stay away from complex avalanche terrain. Use snowpack tests to identify facetted weak layers and strong-over-weak snowpack structures. The most problematic slopes may be where you find older wind-drifted slabs over facets or the Jan 31st crust-facet combination, 2-3 feet below the surface. 

     

    (2/26/2024) Crown line of a very large avalanche visible beneath the cliff band. This avalanche may have run on deeper weak layers. Blue Lake Peak Photo: John Barkhausen

Avalanche Discussion

Observers reported another foot of new snow on Wednesday, and about 2 feet of recent storm snow since February 25th.

This week, observers triggered a small but wide-breaking avalanche in wind-loaded terrain at upper elevations. A few natural avalnaches have been observed, including a wide avalanche beneath cliffs in Blue Lake cirque that appears to have stepped down to a deeper layer. The observers in this drainage found lots of whumphing collapses and confirmed the instability was on a layer of faceted snow 2ft down above the late January crust.  

Before the recent stormy pattern started on Sunday, observers had been finding weak surfaces, including surface hoar and facets, sometimes overlying a thin sun crust. On shady slopes, at mid and upper elevations, there is up to 2.5ft of recent snow over the stronger crust from January 31st. Observers have found a thin layer of weak facets just above this crust. Lower elevations hold substantially less new snow and often don't harbor faceted grains.

Snowpack information is limited outside of the Highway 20 corridor and Harts Pass. Let us know what you find if you get out into the backcountry!

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