Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

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

In sintesi

Greater avalanche danger is found anywhere the wind transported light new snow into unstable slabs. Steer around steep slopes with recent wind loading on lower-angle terrain. Deep snow hazards still exist, especially where you could fall into a tree well or some other terrain feature. Stick with your partners and keep them in sight at all times.

Update @ 8:45pm:  A second cornice triggered slab avalanche was reported on Table Mountain in the Baker Backcountry. Slightly warmer temperatures are forecast for Sunday. Avoid travel directly below large cornices and don't linger if your route takes you near the line of fire.

Problemi valanghivi

  • Wind Slabs

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

    The latest east wind event met expectations with some areas seeing minimal wind effect while nearby terrain got hammered. The most hazardous conditions are found in alpine terrain that holds the largest slabs. The distribution and reactivity of unstable wind slabs will vary across the zone. Evaluate terrain on a case-by-case basis - some slopes could be just fine with others a definite no-go. 

    Look for recently scoured ridgelines and other wind affected features to identify the pattern of wind loading in the terrain around you. A few inches of new snow could obscure some of these clues. Test slopes and hand shears will help gauge wind slab reactivity and depth and can help you identify areas where they are easier to trigger. 

    (2/22/2022)

    Wind slab avalanche last season between Table Mt. and Ptarmigan Ridge in the Baker Backcountry. Southwest aspect @ 5000'.

    Photo: NWAC Public Obs

  • Loose Dry

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

    The new snow is becoming more cohesive but you could still see some sort of new snow avalanche in steep, wind sheltered terrain. These kinds of avalanches are the easiest to anticipate. If you get into steep terrain some amount of snow will probably come down the hill with you. 

    Also, look out for shallow slabs forming at the surface if loose snow becomes cohesive during sun breaks or with more warming than expected. If the sun comes out with any force it could also trigger a round of loose wet avalanches - keep an eye on sunny slopes overhead.

    Example of dry loose avalanches big enough to knock you down and take you for a short ride.

Avalanche Discussion

Reported avalanche activity was not widespread despite the quantity of new snow, but was observed where the wind thickened up the snow to make more of a slab. Natural avalanches which probably released during a period of stronger winds Friday evening were observed on Table Mt. Also, human triggered avalanches were reported from around the Baker Backcountry, generally D1 in size and triggered on short, steep, unsupported features. The most notable avalanche was triggered by a cornice fall Saturday afternoon (photo). No observations were reported from other areas of West North.

All of these avalanches highlight the current snowpack challenge:  the deep new snow is itself fairly stable other than loose snow avalanches, but if wind, sun, or warming have any meaningful impact at the snow surface than the likelihood of seeing or triggering an avalanche increases quickly. It also reminds us that cornices are big, becoming unstable, and are a consideration in backcountry travel for the rest of the winter and spring.

Since March 1st, 2-3’ of light density snow fell across West North with deeper new snow likely in select areas. Though new snow settlement is upwards of 50%, the upper snowpack was observed as already deep and unconsolidated in the week prior to the latest storms. Lower elevation terrain saw temperatures near freezing Saturday so there should be a bit more support if you get off your floatation down there.

 

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