Bulletin d’avalanche

East Slopes North

Northwest Avalanche Center
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Danger d’avalanche

Thu
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 2 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

You can trigger small avalanches where the wind drifts the new snow at middle and upper elevations. You may see small wet avalanches as temperatures warm through the day. Expect another 2" of new snow by Wednesday afternoon with southerly wind.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

    Fresh wind slabs may form in the new snow with southerly winds, but they will be shallow. Steer around drifts on slopes steeper than 35 degrees. Watch for wind-transported snow to show you where slabs are building. You may find slightly older drifted slabs where winds transported snow since the 24th.

    (2/27/2024)

    An example of a skier-triggered wind slab avalanche on February 27th. Fisher Peak, E, 6,900ft

    Photo: NCH

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    1.5–2.5

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

    While triggering avalanches on deeper weak layers may be very difficult, information on the current snowpack structure is limited. 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, softer interfaces adjacent to a crust. The last known avalanches on deeper weak layers occurred around the middle of the month during a prolonged period of very warm temperatures. 

    (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

Expect another dusting of 2" with southerly winds. As temperatures rise in the afternoon, you may be able to trigger small wet avalanches.

Winds stripped upper elevations and drifted the 8-10" of snow that fell on the 23rd. On Sunday and Monday, observers reported triggering small wet avalanches.

Following very warm weather in the middle of March, temperatures cooled. A refreezing upper snowpack (at least at middle and upper elevations) has minimized snowpack concerns for avalanches occurring below the surface snow. 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 weak layers. 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. Where the snowpack stayed mostly dry, you may be able to find a few older weak layers in the upper to middle of the snowpack. These include the March 9th strong-over-weak interface 1-2 feet below the surface. Also, the weak layers of February 25th, mid-February, and the January 31st crust can all be found within 1 foot of each other 2-4 feet below the surface.

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!

Régions couvertes