Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Wed
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

A few inches of new snow and winds may create shallow wind slabs in isolated areas. Older wind slabs are becoming more stubborn, but use caution on very steep slopes near and above treeline. The chances of triggering deep persistent slabs have decreased, but some potential may still exist in shallow, rocky or unsupported shaded terrain.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    A few inches of new snow and winds may create the potential for shallow windslabs on Tuesday. Newly formed slabs should remain soft and shallow during the day, and will probably be limited in extent to steep slopes right off ridgelines at higher elevations. You may still be able to trigger a wind slab in older snow on exposed and unsupported steep features, though. Use caution on slopes steeper than 35 degrees, especially on the leeward side of ridges or on slopes with wind textured snow. Steer around very steep slopes that appear to be loading, or if you find deeper drifts or shooting cracks. 

    (3/3/2022) Wind drifted snow on an exposed W aspect at 7,000ft. Photo: Matt Primomo

  • Deep Persistent Slabs

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

    On the 3rd a very large, deep avalanche was remotely triggered on NE facing terrain near Harts Pass. It has been a number of days since then, and chances of triggering one of these very dangerous avalanches have decreased, but may still exist. The weak layer can be found 3-5' below the surface, so if triggered it would be a very large avalanche. 

    Limit your exposure to complex terrain that may contain large overhanging cornices. A heavy natural trigger like cornice fall could be enough to trigger a deep persistent slab.

    Avalanches have failed on a layer of facets sandwiched between crusts (late January facet/crust combo) inconsistently since early February. Sudden or propagating results in snowpack tests can identify the layer of concern. East of Washington Pass, the snowpack is likely much more shallow, and this interface may be nearer to the snow surface.

    (3/3/2022)

    A very large (D2.5) and widely propagating slab avalanche was triggered by a snowmobile on March 3rd. The crown is estimated at roughly 5ft deep. 6600-6800ft, NE, near Harts Pass

    Photo: Drew Lovell

Avalanche Discussion

We can expect a few inches of new snow, with potential for some upslope enhancement in the south and eastern parts of the zone on Tuesday. This may be a nice little refresher, and should soften up the travel. Professionals noted a few touchy and shallow wind slabs on Sunday beneath ridgelines near Washington Pass. On Monday slabs appeared more stubborn. The new snow is falling on a mixed bag of surface conditions, from sun crusts on southerly aspects, to wind stiffened surfaces on others. There may be some faceted snow on sheltered and shaded slopes, which could make for nice riding conditions. You'll find plenty of avalanche debris beneath steep slopes from a very impactful atmospheric river event 2/27-3/1. 

The snowpack continues to slowly adjust following the last significant storm. Several feet of snow fell (3" of water at Washington Pass) over this cycle, with rain pushing up to around 6500'.  A widespread avalanche cycle occurred over this period with many large and some very large avalanches observed over the following days.  

It's unclear how many avalanches may have released down to the late Jan facet/crust combo during the storm cycle.  However, on Thursday 3/3,  a snowmobile triggered a deep slab. This was a very wide slab avalanche, at least D2.5, at 6600-6800ft, NE, near Harts Pass. The crown was estimated to be 5ft deep and likley ran on the late January facets.  A few other deep crowns were observed in the Hairpin Valley that may have also run on this late January weak layer. Another, more recent layer of concern was buried on February 26th. This layer may encompass facets above and below a suncrust on southerly slopes, and surface hoar and or facets on shaded slopes, but doesn't appear to have caused problems after the last storm. You could find these layers 2-3ft down near Washington Pass. 

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