Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 8 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Avoid steep slopes where you identify signs of recent wind-drifted snow, such as rippled surfaces, rounded drifts, or stiff, slabby-feeling snow. Warming temperatures and possible sun breaks could increase the likelihood of both slab and loose snow avalanches. Take time to assess the snowpack before committing to larger terrain. Pay attention to changing conditions.

Problemi valanghivi

  • Wind Slabs

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

    You may find little to no sign of wind effect in some parts of the forecast zone on Friday, but wind slabs become more likely the farther south you travel. Let signs of recent wind transport—scoured ridgelines, fresh cornices, or recent avalanches—drive your terrain choices. Track changes in snow stiffness as you move across aspects or gain elevation, and gather information about upper snowpack layering before committing to steep, wind-exposed terrain.

    (12/29/2021)

    Example of a small wind-affected feature showing both wind scouring and loading in close proximity.

     

  • Storm Slabs

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

    Warming temperatures may allow a stiffer surface slab to form over colder, lighter snow below, increasing slab reactivity. These slabs should be small and shallow, but larger, older slabs may still lurk on very steep, unsupported slopes.

    Use test slopes and simple observations to assess how well the new snow is bonding before committing to bigger terrain. Shooting cracks, whumphing, and recent avalanche activity are red flags to steer towards lower-angle slopes. When in doubt, choose a lower-angled option and avoid slopes with terrain traps in the runout below.

    (1/1/2023)

    Slabs on steep slopes getting primed by a bit of sun or warming are where you could find one of these on Friday.

    Photo: Jeff Hambleton

Avalanche Discussion

Uncertainty remains elevated in Friday’s avalanche forecast. While there are signs the snowpack is trending toward better stability, strong to extreme winds and intense loading at Stevens Pass raise questions about whether similar conditions developed in parts of West Central—questions that will likely only be answered through field observations.

The biggest unknown is variability in wind loading. Some areas appear to have seen little to no recent transport, while others show signs of wind-affected snow and lingering sensitivity. Rising temperatures could also increase slab reactivity, especially if soft surface snow stiffens into a slab over colder snow below. Cloud cover should limit solar input, but any extended sun breaks on southerly aspects could produce loose snow avalanches, given the amount of low-density snow available.

Recent avalanche activity adds another layer of uncertainty. While many avalanches from this cycle resembled typical new-snow and wind slabs, a few larger slabs with wide crowns were observed in mid-slope terrain. No buried surface hoar or persistent weak layers have been confirmed; however, short spells of clear sky between recent storms leave open the possibility that thin weak layers formed and were quickly buried in a very spotty and inconsistent manner.

Anticipated conditions on Friday don’t point to a single, simple message. Instead, they demand attention to detail—where the wind blew, how the snow feels underfoot, what the sky is doing, whether it's getting warmer, and if recent avalanche activity lines up with what you expect to see. Good observations and terrain choice will, as always, be the best way to manage uncertainty.

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