Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
Vedi sulla mappa

Pericolo valanghe

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

In sintesi

New snow and strong southwesterly winds will build fresh drifts and create dangerous avalanche conditions at upper elevations by Wednesday morning. Use visual clues to identify and avoid areas of wind loaded snow on slopes 35 degrees and steeper. 

Problemi valanghivi

  • Wind Slabs

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

    Areas of wind drifted snow will likely be reactive to human traffic near ridge crests, on rollovers, and in unsupported terrain. Be especially cautious around big, open alpine slopes and on northerly aspects. Fresh drifts may even extend down below treeline.  Avalanches could fail at the old/new snow interface or within new snow. Natural avalanches are possible at upper elevations and could grow large (D2). The most dangerous conditions will exist in the early morning hours Wednesday. 

    Pay attention as you transition into wind affected terrain. Watch for blowing snow, fresh cornices, and lens-shaped pillows as evidence of the wind slab problem. Assess new and wind drifted snow as you travel, and look for cracking, collapsing, and recent avalanches. Choose sheltered, lower angle terrain, and steer around convex rollovers and slopes below cornices.

    (11/23/20) Shallow wind slab (D1) failed naturally within recent wind drifted snow on a north aspect at 4500ft near Austin Pass in the West North zone

Avalanche Discussion

Precipitation transitioned from rain to snow Tuesday afternoon, and snow levels will continue to drop to  2000ft overnight during the brunt of the storm. An additional 6-12in of new snow could accumulate by Wednesday morning and looks to be accompanied by strong southwesterly winds.  Dangerous avalanche conditions are expected at upper elevations. Ease into terrain slowly, and steer around wind loaded slopes greater than 35 degrees.

With all the recent snow and backcountry traffic, several natural and human triggered avalanches were reported in the Central and Northern Cascades already this season. Most avalanches were small (D1), and occurred within new and wind drifted snow in north-facing upper elevation terrain (Observation, Observation). Wet avalanche activity also occurred during a rain event on Nov. 18 (Observation). The lower snowpack is still moist from the rain last week, but strong and uniform. Continuous snow begins near 2500ft. A sharp uptick in the height of snow occurs near 4000ft. Remote weather stations in the adjacent West North and Stevens Pass zones report 40-60in of settled snow on the ground (above average for this time of year). 

Despite the impressive November snowfall, early season conditions still exist. Stay alert for open creeks, tree wells, crevasses, or other exposed hazards. Consider the consequences when choosing terrain. Falling or getting caught in even a small avalanche could result in a rough ride in these conditions.

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.

Regioni coperte