Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Wed
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Highlights

Very dangerous conditions will extend into Tuesday as very large and destructive avalanches could occur naturally at upper elevations. The wind will drift snow near and above treeline and continue to stress older weak layers. You can trigger wet avalanches big enough to bury you where rain fell below treeline.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    2–3

    Travel in avalanche terrain at upper elevations is not recommended. Avoid being near or under leeward sides of ridges. Stay off of slopes 35 degrees or steeper where the wind has drifted slabs of snow.  Even below treeline, make sure to stay out from under avalanche paths that could run down from above. This is not a day where you can manage the risk by simply steering around small drifts. You will need to consider the potential for wind loading to result in a much more dangerous persistent slab avalanche.

    Ongoing southwesterly winds will continue to drift slabs of snow on leeward sides of ridges near and above treeline. While the precipitation will taper off by Tuesday morning, the wind will continue to add a load to upper elevation slopes.

    (2/27/2022)

    The crown of a natural windslab (D1) with wind transport visible. WSW, 6,700ft, Cutthroat creek drainge

    Photo: Josh Hirshberg

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2.5–3.5

    Stay off of, and well out from underneath steep slopes while this storm continues to load upper elevation slopes. Avalanches could encompass entire starting zones and run full paths to valley bottoms. Persistent slab avalanches are the source of the majority of avalanche fatalities and the risk is very difficult to manage. Avalanches could now be very destructive and unsurvivable. Only travel in the backcountry if you're confident in your ability to avoid avalanche terrain.

    While the late January facets have recently been dormant, they've remained weak on shaded aspects at middle and upper elevations. A huge load of recent snow may have made it easier to trigger the layer. There's uncertainty about this and until we know more, proceed with extreme caution.  Near the Cascade crest, you can find this layer about 3-4ft deep and sandwiched between two crumbly crusts. Further east this layer is closer to the surface and could be easy to trigger. Very wide avalanches were observed on it earlier this month. Additionally, a layer of facets (adjacent to a thin crust on sun-exposed slopes) was buried on February 26th. There's some evidence that this weak layer could continue to produce surprising avalanches.

     

    (2/12/2022)

    A natural D1.5 avalanche, occurred Feb 10 or 11th, likely on the late January pwl. Porcupine Pk, E, 7,400ft.

    Photo: Tino Villanueva

  • Loose Wet

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

    You can trigger wet avalanches in the new snow on slopes 35 degrees and steeper. If you see wet snow that slides easily, stay off of slopes 35 degrees and steeper. Rain fell to at least 5,000ft and may keep surfaces moist through Tuesday. Many steep slopes already avalanched, but some could still pose a hazard. An interface buried on Saturday as well as crusts just under the recent snow could still produce avalanches big enough to bury or kill you.

    (1/26/2022) Debris from multiple, overlapping wet avalanches, up to size D2.5, that occured roughly between Jan 12-22nd.. Below pt 6932 near Rainy Pass Photo: Josh Hirshberg

Avalanche Discussion

Heavy snow, rain, and very dangerous conditions limited access on Monday. Observers near Harts Pass reported widespread natural avalanches in the new snow, even on small, low-angle features. By Monday evening, they reported 3 feet of accumulated storm snow. In that same time, the Washington Pass weather station reported 26 inches of snow and 2.04" of water equivalent. The overall height of snow gained  38" since the 26th at Washington Pass.

On Sunday, observers in the Cutthroat creek area found touchy avalanche conditions with about a foot of new snow fracturing easily on steep slopes. One large soft slab up to 1.5ft deep was noted from a SE aspect at 6,700ft. On a similar slope, observers reported remotely triggering a slab avalanche, likely on the 2/26 interface. Numerous small (D1-1.5) loose avalanches were also observed from upper elevations. NWAC Forecaster Josh Hirshberg found the late January facets about 2.5ft down on a north aspect in Cutthroat creek, with propagating test results (ECTP23, PST 30/100 End).

On Friday observers found surface conditions to consist of a mix of weaker snow grains; patchy surface hoar and near-surface facets on northerly aspects while widespread surface hoar had grown on southerly aspects. These layers could become the next, widespread problem as the storm tapers off. 

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