Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
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Pericolo valanghe

Fri
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
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

Rising freezing levels and sunshine could help the snow to fall from trees, rocks, or cliffs to trigger avalanches. If you are standing in the sunshine and the snow surface is wet and sticky, take note of what could fall on you from above and head toward shaded slopes.

Problemi valanghivi

  • Loose Wet

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

    The clouds should dissipate, leaving us in bright sunshine with rising freezing levels on Thursday. Take a look at the snow surface where you are traveling to determine if the sun’s influence has made it warm and sticky. If so, the recent storm snow could destabilize and produce some Wet Loose avalanches. These avalanches will be more likely on slopes that see direct sunshine and could be larger as you ascend in elevation. These slides often start at a point and can entrain snow, fan-out, and even trigger slabs as they descend downhill. Besides taking note of the snow surface, you can look for precursors to Wet Loose avalanches such as pinwheels and rollerballs as an indication to head toward shaded slopes to avoid this hazard. 

    (3/9/2021) Rollerballs and pinwheels were already observed within the zone the past few days with filtered sunshine. On Thursday, we expect to see more of these and some actual Wet Loose avalanches due to more sunshine and rising freezing levels. [Photo: Enji Cooper]

Avalanche Discussion

Filtered sunshine and some warm temperatures have already graced the pass over the past few days, but Thursday should be a notch up in the good weather department. The past few days may have already produced some rollerballs or small Wet Loose avalanches, but we expect a more widespread cycle on Thursday involving the recent storm snow over the 3/5 crust. This warm-up should have you thinking about where else snow could fall to create a hazard. Cornices and Glide slopes are the first things that come to our minds, so give these ticking time bombs a wide berth by not traveling under them until temperatures start to cool again. If you find yourself avoiding direct sunshine on shadier slopes, you could find cold dry snow still exists and some lingering Wind Slabs at upper elevations to steer around.

We have decided to remove the Deep Persistent Slab problem from our official problem list at Snoqualmie Pass. Although the weak snowpack structure remains, a few data points have made us feel more comfortable with this layer than we have recently.

  1. Our last confirmed natural avalanche on the Mid-January crust/facet layer at Snoqualmie Pass was over a week ago. (The Chair Peak slide on 2/28-3/1). The last suspected avalanche on this layer throughout the region may have been a few days later in the West South.
  2. We have a generally strong and well-settled upper snowpack above this layer. This includes the most recent 3/5 crust, which is thick and supportable in most locations throughout the zone.
  3. Since our last major loading event on this layer, test results have become more inconsistent than they were previously. 

The Mid-January crust still remains 8-10 feet deep in the snowpack throughout much of the zone, and we believe it is currently dormant. It may wake back up at some point this season, however. At that point, we will put it back on the official problem list and continue to talk about the dangers this layer presents. Until that time, don’t forget about this layer. If you choose to enter more complex or large avalanche terrain, you should continue to talk with your partners about the low-likelihood/high consequence avalanches this layer is capable of producing. Keep in mind that when they occur, these avalanches have broken trees and descended far distances toward their maximum runouts in valley bottoms. The best way to mitigate your risk is to limit your time in and below large avalanche start zones, paths, and runouts. 

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