Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Thu
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

Very large and unpredictable avalanches continue to occur naturally throughout the zone and should drive your decision-making and terrain selection. Be leery of large start zones, avalanche paths, and their runouts.

Problemi valanghivi

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    3

    Very large natural avalanches have been occurring across the Cascades and the West South and are suspected to have run on the Mid-January crust/facet combo. This interface has recently been measured close to 7 feet deep (200cm) near Crystal Mountain. This depth will vary across the zone, with it suspected to be over 10 feet deep near Paradise. We have had several rounds of deep slab avalanches over the past few weeks and many have been erratic and hard to predict. We could go several days without seeing another deep slab release, or we could see multiple happen tomorrow. Know that if you decide to enter large start zones, avalanche paths, or runout zones, that you are putting yourself at risk. Many of these slides have run very far distances and broken trees as they descend, reaching valley bottoms and areas normally considered as “safe”. Being caught in one of these slides would almost certainly be fatal and those consequences should shape your decision-making and terrain selection. 

    (2/28/2021) This slide on Norse Peak was measured to be over 1000' wide and approximately 6 feet deep. It broke trees and is suspected to have run on Friday (2/27)

  • Cornices

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    The recent low-density snow and windy conditions allowed cornices to form on multiple aspects around the zone. The largest and freshest cornices may be found on east aspects, but take a look to the ridgelines on any aspect and see if these beasts lurk above you. Sunny weather and rising freezing levels may be enough on Wednesday to destabilize cornices and let them fall on the slopes below. These large triggers could be the cause of slab avalanches to fail or may have plenty of snow themselves to pose a hazard. Give these ticking time-bombs a wide berth on Wednesday by not traveling below them or getting close to them if you’re on a ridgeline.

    (2/28/2021) Winds have been strong enough in the West South recently to load leeward slopes and build large cornices. These cornices could act as triggers on the slopes below.

  • Loose Wet

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

    Much of the West South has recently seen some sunshine and warm weather, but you could still see some Wet Loose avalanches on Wednesday. These avalanches will be most likely on slopes that see direct sunshine and often initiate at a point such as near rocks or trees. These slides can entrain significant snow, fan-out, and even trigger slabs as they descend downhill. Rollerballs, the snow surface getting warm and sticky, or snow shedding from trees and rocks will be your first indicators of Wet Loose avalanches. If you notice these signs or recent avalanches with fan-shaped debris piles, head for shadier slopes keeping aware of the terrain above you.

    (2/28/2021) Pinwheels and rollerballs were observed on Sunday (2/28) in the West South and are a good indicator that wet loose avalanches are possible. [Photo: Enji Cooper]

Avalanche Discussion

We have confirmation of very large (D3+) natural slab avalanches running on Friday, Saturday, and Sunday in the Crystal Mountain backcountry. On Monday, a large natural was reported to have run near White Pass. That’s 4 consistent days with a natural avalanche large enough to kill you in the West South. We haven’t heard of any yet on Tuesday, but observations have been limited. These slides may not have initiated at lower elevations, but many of them ran far distances toward valley bottoms, meaning that generally safe avalanche conditions do not exist, even below treeline.

On Wednesday, sunshine and warming temperatures have us worried about natural avalanche activity continuing. When the snow starts to warm up, it generally starts to fall off of things. This means that cornices may fall and trigger deep slabs, or blocks of snow and ice may fall off rocks and cliffs to trigger avalanches on the slopes below. Even snow falling off trees and rocks may start as a simple snowball and grow into a large avalanche as it descends. Let the deep persistent slab problem continue to guide your decision-making on what terrain is within your acceptable level of risk and stay safe out there.

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