Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Fri
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

You can easily trigger avalanches at upper elevations where the wind drifted 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.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Use extra caution on leeward sides of ridges and terrain features. Watch for triggering avalanches where the wind drifted slabs of snow on Tuesday. Look and feel in the snow for clues such as stiffer, deeper drifts, or sculpted surfaces. Steer around convex roll-overs and slopes 35 degrees and steeper. Continue to avoid unsupported slopes and terrain where avalanches in the recent snow may overlap with the deep persistent slab problem. Give the new snow and wind drifted areas time to heal and travel on less steep and more supported slopes. 

    Over 14" of snow accumulated near Washington Pass by Tuesday night. The snow landed on a variety of surfaces from moist melt forms at low elevation to crusts or old wind-pressed snow.  Avalanches in the new snow could still be possible wind-sheltered slopes on shaded NE-NW aspects where you find underlying weak facets. 

    (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

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–3

    The chances of triggering deep persistent slab avalanches are slim, but not impossible. Be especially 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 and unsupported terrain, 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

Following a storm earlier in the week, the new snow has been slow to bond to the variety of old surfaces. On Wednesday, observers triggered a couple of small slab avalanches involving the recent snow near treeline on northeast and southeast aspects of Kangaroo Ridge.  On Tuesday, observers reported seeing and hearing natural avalanches in the Hairpin Valley. They were able to trigger storm slabs avalanches on steep northerly aspects in the Hairpin Valley and wind slab avalanches on the new/old interface on a WNW aspect at 6,800ft on Kangaroo Ridge. 

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. The most recent of these was triggered on March 9th in Allen Basin. See the avalanche occurrence database for details. 

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