Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

You may be able to trigger avalanches at upper elevations where the wind drifts recent snow. Use quick tests and small test slopes to check how easily the snow slides before traveling on steeper slopes. Avalanches in deeply buried older layers are very 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

    Use caution on leeward sides of ridges and terrain features. Look and feel in the snow for clues such as stiffer drifts, or sculpted snow surfaces. Steer around convex roll-overs and slopes 35 degrees and steeper where you see evidence of drifting. 

    Light snow accumulations and increasing wind will form slabs over older wind drifts, formed on the 15th. Existing soft snow could be transported and contribute to fresh wind slabs. In most places, older wind slabs will be difficult to trigger. An exception could be on shaded, northerly aspects above treeline where wind-drifted slabs could rest on weak snow.

    (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

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    2–3

    The chances of triggering deep persistent slab avalanches are slim, but not impossible. Be cautious in areas with a shallow snowpack such as wind-scoured slopes and parts of the range that are further east or north such as near Harts Pass. You can limit your exposure to large start zones and very steep slopes, especially those with big overhanging cornices (see photo).  Also, avoid complex, shallow, rocky areas, and unsupported slopes.  

    (3/10/2022)

    In the center of the photo is a recent D2.5 deep slab, likely triggered by a cornice fall. 

    To the right of the photo, you can see a similar-sized avalanche that likely occurred during the natural cycle of 2/28-3/1.

    McGregor Mtn, NNE, 7,200ft.

    Photo: Matt Primomo

Avalanche Discussion

On Friday, you may find more new snow and avalanche danger west of Washington Pass. It appears that storm snow from earlier in the week is generally bonding well.

A storm on the 15th delivered over 14" of snow near Washington Pass with nearly 2 feet near Rainy Pass. Tuesday was a particularly active day of natural and triggered avalanches. On Wednesday, observers were still able to trigger small slab avalanches in the storm snow near treeline on northeast and southeast aspects of Kangaroo Ridge. No new avalanches were reported on Thursday. The storm of the 14-15th buried a variety of surfaces from moist melt forms at low elevation to crusts or old wind-pressed snow. A thin layer of near-surface facets may have survived on NW-NE aspects near and above treeline. This layer (buried in some places on March 8th) has been the source of impressively dangerous persistent slab avalanches near the Mount Baker ski area and in the West South zone. 

After a widespread avalanche cycle on 2/28-3/1, observers reported a number of deep crowns from avalanches that likely ran on the late January weak layer.  The Harts Pass area has seen a concentration of avalanches on the late January weak layer in the past month. The most recent of these was triggered on March 9th in Allen Basin. See the avalanche occurrence database for more details. 

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