Bollettino valanghe

West Slopes Central

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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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

You might encounter wet snow avalanches running in the new snow layers if temperatures warm enough, and there's a chance that thicker drifts of snow at upper elevations could avalanche with a human trigger. Remain aware of the small chance that very large avalanches could release with a large trigger such as a cornice drop on northerly, above treeline slopes. 

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    Wednesday night delivered 6+ inches of dry snow to mid and upper elevations in the West Central Zone. Freezing levels rising to 4000 feet Friday afternoon could moisten the previously dry snow and cause wet loose avalanches. If we get any sun breaks through the clouds, expect south-facing slopes to quickly moisten and release. Overcast skies will lead to a more equal avalanche problem on all aspects. The intense spring sun is tough to predict, and wet snow may be found at far higher elevations than our forecasted freezing level.   Avalanches are expected to stay relatively shallow, only in the top couple inches of snow. Pay attention to how much snow is running down as it gets wet. If it starts getting more than a couple inches deep, or entraining all the new storm snow, steer away from nearby steep slopes and stick to lower angle terrain. 

    Pay attention to how much the snow moistens, and if you're seeing any rollerballs or avalanches like these one running down. If you do see any that start running deeper, steer away from steep nearby slopes. 

    Photo: Public Observation

  • Deep Persistent Slabs

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

    A layer of faceted snow 4-8 feet deep is likely behind very large avalanches that occurred recently. Though you're more likely to encounter a shallow avalanche Friday, the rare deep slab avalanche will be much more dangerous if you happen to be in the way.  It’s quite unlikely a single person could trigger one of these avalanches but they could still be provoked by a big load like cornice fall, slab, or loose snow avalanche from above. Overall the danger from these is diminishing as colder temperatures make for less cornice fall and other natural activity. That being said it’s still a good idea to not linger on big, northerly alpine slopes below cornices or other hazards. We'll have our eyes on this problem as a large system approaches at the end of the weekend. 

    (3/27/2022)

    Very large (D3) deep slab avalanche below Hidden Lake Lookout in North Cascades National Park. Likely triggered by a chunk of cornice falling from above. Northeast aspect at 6700'.

    Photo: John Scurlock

Avalanche Discussion

Isolated wind slab pockets that you could trigger an avalanche in might still exist in upper elevation terrain. These slabs may have settled and strengthened a bit since they first formed 24+ hours ago. Regardless, keep an eye out for small, isolated pockets that you could trigger around rocky outcroppings, in gullies or on leeward slopes on steep upper elevation features. Avalanches in these drifts probably wouldn't be large enough to bury you if you triggered one, but if you're near a terrain trap they could still cause harm.

This spring we've jumped between wet and dry snow problems frequently, as unsettled weather patterns and temperature swings continue. In this variable weather large cornices are losing strength. Give them a wide berth. We have a brief reprieve from stormy weather today, before another small storm approaches Friday night. Continue staying alert as you travel in the backcountry, as conditions are constantly evolving and we're not into a spring cycle yet. 

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