Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Tue
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Triggering a slab avalanche is likely as more snow falls Sunday night. Expect the most reactivity in mid to upper elevation wind affected areas, however avalanches may occur on other steep slopes as well. Stay off terrain steeper than 35 degrees, especially where you identify wind loading.

Problemi valanghivi

  • Storm Slabs

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

    In the West North zone several reports of skier triggered slab avalanches came in over the weekend, with conditions similar to what we've seen in the West Central zone. You can check out some observations HERE and HERE. Expect natural and human triggered slab avalanches to occur on steep slopes on Monday.  You will find them most reactive in upper elevation areas where wind loading occurred. Avalanches could break within layers of new and wind drifted snow, or on variable old snow surfaces buried Thursday (3/18).  Small dry loose avalanches also may run on the surface of steep slopes. Pay attention to the layers beneath the new snow, as melt freeze crusts were present before the storm on the southerly half, while direct northerly aspects above approximately 4500ft held dry snow. Weak snow may have formed at the surface of the dry snow during the high pressure over the last week, so avalanches may fail easier at that interface. 

    Dig down to the new snow/old snow break to investigate how readily snow slides at the interface, or on layers within the new snow. Seek out small slopes before committing to larger terrain. Avoid slopes greater than 35 degrees, especially in areas where they are wind loaded.

    (3/20/2021) A skier triggered storm slab avalanche in the West North zone on Saturday. The crown was 30-40cm deep, propagating 100+ft. D1. Photo: NWAC Observation

Avalanche Discussion

Since March 18, at least 2 feet of snow will have fallen in the West Central zone by Monday morning. Our avalanche problems are limited to new snow, but this is an impressive amount, especially in wind loaded areas where there will be more. It is a welcome reprieve to be back to winter conditions, but avalanche risks are elevated with the return to winter. Keep this in mind as you enjoy the fresh powder. 

Cornices are continuing to increase in size and weight. They could drop onto slopes below acting as huge triggers. Stand back from cornices along ridgelines and minimize overhead exposure to these features. Several large glide cracks and a few glide avalanches were observed recently as well. Cooling temperatures should limit glide activity for now, but these avalanches are difficult to predict. If you notice crevasse-like cracks in the snowpack, avoid slopes beneath those features.

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