Bollettino valanghe

West Slopes North

Northwest Avalanche Center
Vedi sulla mappa

Pericolo valanghe

Mon
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
Open full map
Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Avalanche danger will increase through the day as snowfall and wind start to build fresh slabs. Be ready to shift towards simpler terrain if the snow starts to pile up and visibility deteriorates. Look out for cliffs shedding snow and wet avalanches at low elevations.

Problemi valanghivi

  • Storm Slabs

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

    With falling snow levels, dry snow should form fresh slabs at mid and upper elevations. You are most likely to trigger one of these avalanches in wind-loaded terrain. But changes in temperature or snowfall intensity can create shallow instabilities in wind protected terrain as well.

    Most areas should see moderate snowfall and wind speeds. Schriebers and the Baker BC - sub-zones favored by south winds - should see the most snow, strongest winds, and greatest avalanche danger. 

    It should be pretty easy to track the depth and distribution of new and wind-drifted snow over the old, wet surface below. You can evaluate how well the new slabs are bonding with simple tests like slope cuts, skin track tests, and hand shears. Blowing and drifting snow will show you which slopes could be wind-loaded. Stick to more sheltered, lower-angled terrain to reduce uncertainty during stormy conditions.

    Example of the kind of slab you might find on Sunday.

  • Loose Wet

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

    Above-freezing temperatures and rainfall will persist at low elevations. Steep terrain holding wet snow should still be on your radar until it gets colder. Avalanches and other signs of instability are surefire signs that overhead terrain is about to shed snow. Better yet, avoid the problem by looking for and staying away from unstable snow perched above before it decides to come down. You are most likely to see this on rock slabs and cliffs, but any steep slope could still produce some sort of avalanche if provoked enough.

    If snow levels end up higher than forecast we could see legitimate rain and more wet avalanches at mid-elevations.

     

    (1/19/2024)

    A small slab avalanche triggered by a wet loose avalanche that released in the terrain above.

    Photo: Julz Holder

Avalanche Discussion

Saturday was a mixed bag in terms of observations. On one hand, most observers felt stability had improved as the snow settled and adjusted to rain from Friday. It was more difficult to get wet snow moving on steep slopes and no active avalanche activity was observed. But reports and photos of wet loose and slab avalanches poured in all afternoon - it looks like there were just too many to count. While most were the typical D1-1.5 in size, several were larger including a handful of very large slab avalanches with deep crowns. The latter appeared to have been triggered by wet loose avalanches or cornice falls from above.  Avalanches were observed on all aspects and at all elevations. It's likely that many of these released between Friday late afternoon and Saturday morning during the peak of warming and/or rainfall.

The upper snowpack is now wetted out 6-10" down from the surface. Stability and slope tests have been unremarkable, with no new human-triggered avalanches reported other than a few rollerballs or small push-alanches. Snow conditions were not awesome but the denser, settled snow surface made for easier travel than thick wet snow on Friday. While not a major concern, deeper slab avalanches show that there are still less than bomb-proof layer interfaces above the 12/30 crust. It just takes a really, really big trigger to get one of these slabs moving. 

 

 

Regioni coperte