Boletín de aludes

East Slopes Central

Northwest Avalanche Center
Ver en el mapa

Peligro de aludes

Wed
Alta montaña
3 · Notable
Límite del bosque
2 · Moderado
Bajo el límite
2 · Moderado
Open full map
Desactualizado: este boletín caducó 6 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Triggering an avalanche in wind drifted snow will be possible Tuesday despite the transition to clear and sunny weather. A weak layer of snow exists between the recently wind transported snow and the old firm surface. Identify where wind deposited recent snow and stay away from lee slopes steeper than 35 degrees where you see evidence of wind affected snow such as cornice development and pillow-like drifts.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    Very strong winds and new snowfall built shallow but reactive wind slabs Monday. Wind slabs which you could trigger Tuesday will be thicker, but still widely propagating. Wind transport was intense, however, snow accumulation was modest at lower elevations and in the eastern part of the zone, so expect larger potential avalanches as you ascend. The onset of precipitation Monday morning coincided with plummeting temperatures and, as a result, Monday's snowfall is poorly bonded to the weak snow surfaces from the weekend's nice weather. A layer of low-density snow lies between the weekend's wind scour and still enlarging wind slabs. In wind-sheltered areas near and below treeline, a layer of surface hoar has been preserved. Regardless of the culprit, a layer of reactive snow is buried between Monday's wind affected snow and the firm or weak surfaces from the weekend. Take note of recent cornice development, give them wide berth and steer around slopes directly below cornices where snow deposits are likely. Identify and avoid wind loaded slopes where you see firm and textured snow surfaces, cracking or whumphing in the snow as you travel, and pillow-like features.

    As always, use surface textures and cornice formation as visual clues where slabs may be forming. Hollow sounding and firm or textured snow are other clues that wind transport has built slabs. The winds have been strong enough that slabs have developed further downslope than normal so be alert for cross-loaded terrain features and midslope slab formation. Winds are forecast to shift direction and freshly drifting snow will cover some of our most obvious clues to wind slab formation. Choose terrain conservatively through this transitional weather period and choose conservative routes away from start zones and steep lee slopes when in doubt.

Avalanche Discussion

Snowpack height and coverage varies significantly in the East Central zone. Areas near the cascade crest have a substantial headstart over the snowpack at low elevations and near Highway 97. Monday's weather has mimicked this pattern keeping the more eastern peaks relatively dry while peaks nearer to the Cascade crest received a decent shot of snow. Regardless of where you are in the East Central zone, Monday's strong winds have changed the snowpack.

At upper elevations, surface conditions are generally firm and wind-affected making for a good sliding surface as wind slabs form. Cornices have grown in the past couple of weeks and will continue to develop quickly as strong winds and new snow flew Monday. At sheltered locations and on shady slopes weak snow surfaces are likely. Monday, NWAC forecaster Matt Primomo, found widespread surface hoar preserved in the Teanaway mountains on all aspects (including solar aspects) above 5000'. This echos findings from nearby forecast zones. This could be a potentially reactive layer, especially where wind slabs form above it. Observers in neighboring zones found shallow and easily human triggered wind slabs. These are likely to remain active Tuesday.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

Regiones cubiertas