Boletín de aludes

West Slopes Central

Northwest Avalanche Center
Ver en el mapa

Peligro de aludes

Tue
Alta montaña
2 · Moderado
Límite del bosque
1 · Débil
Bajo el límite
1 · Débil
Open full map
Desactualizado: este boletín caducó 5 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

You may trigger an avalanche in wind-drifted snow at upper elevations. Identify and cautiously approach steep terrain where you find dense slabs poorly bonded to the firm crust below. Anticipate increased danger if new snow amounts are greater than forecast  and you find new slabs deeper than 6".

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–1.5

    Light amounts of new snow and strong winds will create shallow wind slabs at the highest elevations. They may have a poor bond to the slick, frozen crust at the current snow surface. Though small, these wind slabs still pose a risk to backcountry travelers in steep, exposed terrain. 

    Monitor new snow depth and the extent of wind transport as you ascend. Use visual cues like scoured snow surfaces and cornices to figure out where unstable winds slabs could be lurking. Use simple tests in safe areas to see how well these slabs are bonded to layers below - or simply bypass steep wind loaded features on lower angle, planar terrain.

     

    Example of small wind slab avalanche in wind affected, alpine terrain.

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely
    Tamaño
    1.5–2.5

    There is still a low likelihood of triggering an avalanche in crust-facet layering from late January. Though no new human triggered, persistent slab avalanches were reported, two more natural avalanches were observed in the last week on Shuksan and Table Mt. 

    • The snowpack structure is inherently weak at these interfaces and is taking time to gain strength.
    • The layers are still reactive above 5400’ on aspects that did not receive strong sun in late January.
    • Reported natural and human triggered avalanches continue at the same aspects and elevations. 
    • They occurred where there are 2 or more feet of new snow over the crust-facet layering.
    • Snowpack tests produce inconsistent results at the crust-facet layering, sometimes even in the same snowpit.
    • Many steep slopes - some very near avalanches that released in the same layers - have been ridden and skied with no results.

    (2/12/2022)

    Faint crown of a very wide natural avalanche suspected of failing in the January 30th crust-facet layers last week. West of the White Salmon Glacier on Mt. Shuksan, north aspect at 6000'. 

    Photo: Lee Lazzara

Avalanche Discussion

Monday will mark a transition away from wet avalanches with colder temperatures through the week ahead. While loose wet avalanches were observed over the weekend in terrain with direct solar exposure, activity was limited in scope.

Little is known about the two additional avalanches in West North suspected of releasing in crust-facet layers buried on January 30th. Both were naturally triggered and had rocky, rugged terrain above that may have provided a trigger in the form of rock or cornice fall or a smaller avalanche. Warm temperatures, greenhouse conditions, or wind loading in the last week could have been the root cause of either. 

Currently, 30-70cm of settled snow overlays the January 30th crust interface. New snow interfaces above the crust are gaining strength. Faceted snow between various crust layers is rounding but still produces sudden results with compression tests and large column tests still point towards propagation. 

Surface conditions will make for challenging travel where little new snow accumulates. A very firm melt or sun crust can be found on solar aspects and all aspects below treeline. 1-2cm of breakable crust with dry snow below was found on upper elevation, shaded slopes.

Regiones cubiertas