Bollettino valanghe

West Slopes North

Northwest Avalanche Center
Vedi sulla mappa

Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
Open full map
Non aggiornato — questo bollettino è scaduto 6 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Loose dry avalanches will be the main concern on Friday. Low-density surface snow is widespread and could form shallow wind slabs if winds increase, especially in exposed alpine terrain. Watch for drifting snow and signs of fresh loading. Reactive wind slabs have already been observed at mid-elevations in North Cascades National Park.

Problemi valanghivi

  • Loose Dry

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

    Small loose dry avalanches are possible on slopes steeper than about 40 degrees. While generally small, they can entrain enough snow to carry you downhill, especially in sustained fall-line terrain. Consequences increase above gullies, cliffs, or other terrain traps. Pay attention to how much snow is moving downhill with you. Have a plan to pull over and let it run its course if it gets to be too much.

    (4/2/2023)

    Dry loose avalanches can run long distances in big terrain.

    Photo: Jason Speer

  • Wind Slabs

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

    Light surface snow is easily transported. Even moderate winds could quickly form shallow slabs near ridgelines, convex rollovers, and cross-loaded gullies. Watch for drifting snow, rounded pillows, hollow-sounding slabs, or cracking underfoot. Test small features before committing to larger slopes and avoid steep terrain that shows recent signs of wind loading.

    Fresh, reactive wind slabs were found in Cascade Pass on Thursday, so some areas have already seen wind transport and have slabs in place.

    (11/21/2023)

    An example of strong wind drifting snow off a ridgeline. Fresh, reactive slabs could be forming on the slope below.

     

Avalanche Discussion

The balance between sun and temperature should limit wet avalanche activity on Friday, but don’t rule it out entirely. Pay attention to sunny slopes overhead and watch for indicators such as rollerballs or pinwheels.

Observers in the Baker Backcountry reported about 10 inches of low-density new snow, no wind effect, and excellent skiing when visibility allowed. One observer high on the White Salmon noted the surface remained soft with minimal wind effect, even at 7,000 feet. Steep southerly aspects will likely have a breakable crust by Friday morning after clear skies and cold temperatures overnight. In contrast, an NWAC forecaster team in Cascade Pass encountered very different conditions. Wind-affected snow was common at upper elevations, and test slopes readily produced wind slabs up to a foot deep. Visibility remained challenging for much of the day due to clouds and moderate snowfall.

While the light snow, cold temperatures, and powder conditions have provided a welcome break from the warm, wet conditions that have characterized this winter, they bring their own concerns. Patches of faceted snow and surface hoar have been identified at several recent interfaces. Also, light-density snow, like what's on the ground now,  facets more readily than the dense snow typical of this region, and cold temperatures slow strengthening. While we still don't have well-developed weak layers like those found in other parts of the Cascades, there is currently enough weak snow out there to not take our typical wet, dense snowfall for granted when it returns.

Regioni coperte