Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Tue
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

New snow and warming temperatures should create a dynamic day with increasing avalanche danger on Monday. Keep wind slabs, storm slabs, and loose avalanches all on your radar as the day progresses. Avalanches in older, deeply buried layers are difficult to trigger, but the weak structure remains.

Problemi valanghivi

  • Wind Slabs

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

    New snow and some wind drifting may continue to maintain the possibility of triggering small wind slabs at upper elevations. A warming trend with the snowfall may create shallow storm slab instabilities during the day, especially in areas further west in the zone. Keep abreast of the changing conditions, and look for signs of instability as the day progresses. Look for shooting cracks in wind-thickened snow, shallow and soft storm slabs on steep convex rolls, and recent avalanche activity.

    Use the most caution on leeward sides of ridges and terrain features. Steer around convex roll-overs and slopes 35 degrees and steeper where you see evidence of drifting. Some shaded, northerly aspects near and above treeline may still harbor old, buried wind slab that could break more deeply on faceted layers. Cornices are also growing, so attempt to minimize your time underneath the honkers as warming temperatures may make them more unstable.

    (3/15/2022) A small (D1) slab avalanche, triggered on a leeward slope on the 3/14 interface. Crown: 14" deep x 25' wide. Kangaroo Ridge, WNW, 6850ft Photo: Josh Hirshberg

  • Loose Dry

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

    Warming temperatures and plenty of loose snow should make for easily triggered loose avalanches on Monday. On shaded slopes, consider stopping every once in a while to see if loose snow runs easily before entering larger features. Sluffs may become larger and more 'wet' in character as the day progresses. Keep in mind overhead avalanche paths, especially those that catch direct solar radiation, as these may warm faster. If you find that its raining on dry snow, then expect more dangerous conditions and stay off steeper slopes.

    Loose avalanche in moistening snow.

    Photo: Matt Primomo

Avalanche Discussion

Monday should be a dynamic day, with the nice cold snow slowly turning to heavier, moist snow in many areas by the end of the day. The real warmup may hold off until later in the evening or Tuesday for this zone, however. In any case, expect changing conditions. If you find more than 6" of new snow and widespread storm-related instabilities, conditions are dangerous so adjust your travels accordingly.  Observers reported a handful of small (D1) wind slab avalanches in alpine and treeline terrain on Sunday, and one small (D1) loose wet avalanche below treeline near Cutthroat. On Saturday, observers triggered loose snow avalanches and a small wind slab avalanche on a northeast aspect near Harts Pass. The storm of the 14-15th delivered over 1-2 feet and brought an active day of natural and triggered avalanches. On wind-sheltered NW-NE aspects near and above treeline, you can find a thin layer of near-surface facets 1-2 feet below the surface and often on a crust. This layer (buried on March 8th in other zones) has been the source of impressively dangerous persistent slab avalanches near the Mount Baker ski area and other parts of the Cascades.

A deeper persistent weak layer exists in the zone. The layer can still be found about 3 feet deep, sandwiched between eroding crusts on NW-NE aspects near and above treeline, and has been particularly problematic in the Harts Pass area. The most recent of these was triggered on March 9th in Allen Basin. While triggering an avalanche on this layer (the late January facets) is unlikely, the consequences could be serious. You can limit your exposure to shallow, rocky areas, and very steep and unsupported slopes. After a widespread avalanche cycle on 2/28-3/1, observers reported a number of deep crowns and avalanches throughout the zone that likely ran on the weak layer. See the avalanche occurrence database for more details.

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