Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Mon
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

You can trigger avalanches in the recent storm snow at middle and upper elevations. These will mostly be wet loose avalanches, though you may encounter drier recent snow above 6,500ft. Expect temperatures and sun to warm the recent snow, up to 10", that accumulated this weekend.

Problemi valanghivi

  • Loose Wet

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

    You can trigger wet avalanches on slopes steeper than 35 degrees, especially above 6,000ft. It may be easiest to trigger slides on E-S-NW slopes as the surfaces warm from sunshine. Watch for signs of instability, like fresh avalanches and rollerballs, that indicate you could trigger an avalanche. Anticipate the chances of triggering avalanches and move to lower-angle slopes to avoid them.

    If you travel to upper-elevation terrain, you may find that the recent snow is completely dry. Be ready to assess for other new snow instabilities, like storm or wind slabs.

    (3/17/2024)

    Wet loose debris on the West aspect of Kangaroo Ridge

    Photo: Willie Webster

  • Persistent Slabs

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

    Until we can be more certain about the snowpack structure, continue to put a large buffer between where you travel and large, complex, and unsupported start zones at upper elevations.

    While triggering avalanches on deeper weak layers may be difficult, it's not out of the question. If you travel on northerly slopes at upper elevations, use snowpack tests to look for weak layers in the middle of the snowpack, 3-4 feet below the surface. These may show up as strong-over-weak layers or very thin, soft interfaces adjacent to a crust. 

    (3/15/2024)

    This crown from Azurite Peak highlights the type of big, alpine terrain where the potential for very large human-triggered or cornice-triggered avalanches remains.

    Photo: Willie Webster

Avalanche Discussion

A spring storm is delivering about 1"/hour of snow to middle and upper elevations at the time of writing. This is likely falling as rain or moist snow at lower elevations. Precipitation should wind down before dawn on Sunday, giving way to clearing and mostly sunny skies. 

The East North zone has finally enjoyed multiple nights with good refreezes at middle and upper elevations. A refreezing upper snowpack (at least at middle and upper elevations) has minimized snowpack concerns for avalanches occurring below the surface snow. However, the new storm snow will accentuate hazards on aspects that stayed colder throughout the recent warmup. That said, we have a lot of uncertainty about the snowpack structure as observations are limited. Be prepared to make your own assessments of the persistent slab problem. On sun-exposed slopes, you may find a new host of layers created by water pooling in the upper snowpack. As these freeze, they should be adding strength to the snowpack. Elsewhere, a few older weak layers to look for include:

-The March 9th strong-over-weak interface 1-2 feet below the surface.

-2-4 feet below the surface, you can find the Feb 25th and mid-February weak layers along with the Jan 31st crust within 1 foot of eachother.

The cornice hazard decreased with the cooling temperatures, but it's worth continuing to be aware of slopes where cornices remain and could fall from overhead. When traveling on ridges, keep plenty of distance from the edge and ensure you're not traveling on overhung snow. Cornice falls are difficult to predict, and they often overhang the slopes where we have the most avalanche concerns. 

Lower elevations and sun-exposed aspects may be significantly melted back. Prepare for rocks, stumps, and frozen avalanche debris that may be shallowly covered by fresh snow or fully exposed.

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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