Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Fri
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

The weather forecast is more favorable for backcountry travel on Thursday, but continue to use caution, especially if you make it to upper elevation terrain. Track and test new and wind-drifted snow layers. Limit travel on or directly under steep slopes where the snow is becoming thick and wet.

Problemi valanghivi

  • Storm Slabs

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

    Fresh snow will continue to accumulate, but in lesser amounts on Thursday. You are more likely to trigger a slab in terrain with active or recent wind-loading, but warming temperatures and rising snow levels mean you could find dense, unstable slabs on any slope, wind-loaded or not.

    Track variations in snow depth and stiffness as you gain elevation and change aspects. You can easily compare new snow depths as there is a crust just below it. Use a ski pole handle or even just dig down with your hand to find the crust. Simple tests like slope cuts and hand shears can help you gauge slab reactivity.

    (4/12/2023)

    A crust is visible in the bed surface of this slab avalanche. This is similar to the layering currently found at the new-old snow interface down 1-2'.

    Photo: NWAC Public Obs

  • Loose Wet

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

    Warm, wet snow at low and mid-elevations will open the door to fresh wet loose avalanches running in layers of new snow. The likelihood will increase if snowfall switches over to rain. Rollerballs and small wet loose avalanches are signs you could see more  - or bigger - avalanches. Use caution on steep slopes with wet, mushy snow, as you can likely get some snow moving with you down the hill if you push hard enough. While some low-elevation terrain does not have the consistent snow cover to allow for avalanches, enough places do have it that it should still be on your radar.

    (3/8/2024)

    Fresh rollerballs are an initial sign the snow surface is warming.

    Photo: Julz Holder - Grounding Truth

Avalanche Discussion

A strong storm with heavy snowfall and gusty winds moved across the Cascades on Wednesday. By day’s end, about 12” of new snow had accumulated in sheltered terrain at mid-elevations in West North and West South. West Central picked up a bit less precipitation, with around a half-inch recorder at most stations. The White Chuck Tripod showed gusts to 9mph, which, given its sheltered location, means there is a good chance it was quite windy. In West North, strong winds redistributed snow onto leeward aspects with drifts of 2’ or deeper.

Observers reported poor visibility for most of the day. Fresh wind-drifted features and slabs were found to be stubborn to trigger in the morning. But a midday warming trend created more of a slab, which was poorly bonded to the crust below. Shallow slabs around 6-8” deep were easy to trigger on convex rolls and other unsupported terrain features.

Be ready for rapid changes in weather and snow stability as we head into the heart of spring. Strong storms can give way to sun and microwave-like warming in a matter of minutes - and then turn back to snow showers by the afternoon. Dry snow avalanche problems can quickly turn into wet snow avalanche problems, or you might see both at the same time on slopes with different aspects. Low elevations have less snow than average after repeated rain and warming events throughout the winter. On the other hand, some are venturing into less traveled areas by capitalizing on easy access that is more on par with April or May.

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