Bollettino valanghe

Olympics

Northwest Avalanche Center
Vedi sulla mappa

Pericolo valanghe

Sun
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
Open full map
Non aggiornato — questo bollettino è scaduto 5 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

You can trigger generally small slabs within wind-stiffened snow above a stout crust. Steer around steep slopes in areas where the snow is cohesive and poorly bonded to the crust. If you hear whumphs or see any signs of recent natural activity, prepare to dial back your terrain selection as there are some lingering concerns in the upper snowpack.

Problemi valanghivi

  • Loose Dry

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

    Dry snow falling since Thursday is low density and may continue to bond poorly to an underlying crust or old snow interface. With cold temperatures remaining through Saturday, this dry snow is likely to remain loose and unconsolidated. You could destabilize this snow on slopes approaching 40 degrees. Evaluate small test slopes before engaging with committing terrain where snow running with you could knock you off your feet at an inopportune moment. Terrain traps can amplify the impact of this loose snow where snow accumulates in a depression or fold on a slope.

    Example: Small dry loose avalanches.

    Photo: Sam Siemens-Luthy

  • Wind Slabs

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

    Winds will be just strong enough to transport recent low density snow Friday night and Saturday. Slabs formed formed on the snow surface from this active and recent wind loading will be more sensitive to human triggering. The recent snow has not been bonding particularly well to the 3/11 rain crust, so it may be easier than you expect to trigger a wind deposit. You'll find mostly low density snow on a crust, but once you identify any of the following wind slab clues - active blowing snow, textured snow, or punchy layering - prepare to identify and steer around steep wind-loaded slopes. Fresh, sharp cornices point toward potentially problematic areas to the lee of ridgelines.

    More uncertainty exists at upper elevations where several day old wind slabs may lurk and the 3/11 crust may fade into oblivion. If you head to these elevations, prepare to assess the upper snowpack before engaging with more committing features.

    Example: Textured surfaces and sculpted snow like this suggest nearby slopes could be wind-loaded. 

    Photo: ONP Rangers

Avalanche Discussion

ONP Rangers evaluated the snowpack on a N facing slope just below Victoria Overlook on Thursday and Friday. The snow above the knife-hard 3/11 crust increased from 2" to 1 ft of unconsolidated snow. The 3-11 crust also thickened to around 2" and became much more supportable by Friday. Of concern, they continued to get easy failures on compression tests within a layer of wet snow below the refreezing crust. The interface of failure had low-density wet snow underneath it. They noted significant settlement at times while traveling and one observer out toward Hurricane Hill heard an audible "whumph" and possibly the sound of a natural avalanche. Given the thickness of the crust, one would expect this to be a new ground, and going forward we think it will be as cold temperatures continue to refreeze the 3/11 interface from the top down. However, the recent snowfall has slowed the progress of the refreeze, so if you find yourself in an area where the crust is not supportable, or if you experience a whumph, or sign of a recent natural avalanche, be aware that this potential concern could linger in your area. The resulting wet slab could be up to 1.5 ft thick, propagate widely, and be difficult to escape. We consider this scenerio quite unlikely, which is why it is not listed as a problem, but it deserves to be on your radar.

Friday was cool with light winds and around 8-10" of new accumulation since Thursday afternoon. Saturday is likely to bring a mix of sun and clouds. In wind-protected areas, wet loose avalanches may be possible on south-facing slopes under direct sunshine. These will generally be small as these slopes lacked coverage prior to the recent storm cycle, but don't linger under sun-cooked slopes once the rollerballs start up.

Coverage has drastically improved at middle elevations with Hurricane Ridge reporting 48" of snow depth and Maggies snow stake reporting 60". Even lower elevations now have some shallow coverage. Coverage remains poor in the trees, on windward aspects, and near ridges. Travel cautiously as rocks or barely submerged obstacles may exist just beneath the snow furface.

Regioni coperte