Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Friday should be a beautiful day at Snoqualmie Pass with sunshine and recently fallen snow. Don’t let your excitement cloud your judgment. There are still overlapping avalanche problems and uncertainty that require your attention.

Problemi valanghivi

  • Wind Slabs

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

    It’s days like Friday where having a “new snow” problem would probably fit the bill quite well. Ah well... At upper elevations, you might encounter lingering slabs where the wind has piled the snow into deeper drifts. Look for these near ridgelines or in confined chutes and gullies. They could even be hidden under a few inches of soft snow from the tail end of the recent storm, so using visual clues may not work. You’ll have to feel for changes in the snow as you travel such as the firmness or depth to help you identify wind-loaded features. Newly built cornices could help give an indication of recent loading patterns.

    Further away from the wind’s influence, Dry Loose may be the most in-your-face avalanche problem you’re dealing with. Look for these to occur on steeper slopes, initiating at a point before fanning out as they move downhill. In isolated locations, the snow could even entrain down to the MLK crust and run fast and far. Be sure not to get surprised by one of these on high-consequence slopes or near terrain traps. There's even a chance that you could also encounter some slabs in wind-sheltered terrain. More on that in the discussion below.

    (1/16/2023)

    A small Wind Slab from earlier this week was triggered on top of the MLK crust near rocky terrain.

    Photo: Public Observation

  • Loose Wet

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

    Speaking of loose avalanches, it should be a beautiful day at the Pass on Friday with a bump in freezing levels and more sunshine. On Thursday, the sun came out and helped produce some rollerballs and shedding snow from cliff bands around the Pass. This doesn’t mean that it is now played out - we could be in store for more on Friday. If you notice that the snow surface is getting wet due to the sun’s influence, snow is shedding from trees and rocks, or see new rollerballs/pinwheels, then you should start thinking about Wet Loose avalanches. Like their dry counterpart, these slides like to start at a point and fan out as they descend. Your best mitigation tactic will be to head for shadier or lower-angled slopes.

    (1/19/2023)

    A Wet Loose avalanche occurred as a result of a tree bomb during a period of sunshine on 1/19. [S 5200']

    Photo: Zack Novak

Avalanche Discussion

Friday should be a bit of a transition day at Snoqualmie Pass, with the possibility of some overlapping avalanche problems for you to manage. The Pass recently picked up close to 15” of snow during this most recent storm, which has added depth over the MLK crust. This should be your baseline for any avalanche you experience on Friday, regardless of its character. 

On Thursday, NWAC forecasters in the Alpental Valley found that the depth over the MLK increased from around 15 inches at lower elevations to closer to 20 inches at mid-elevations. Terrain above ~4500’ was not observed, but the depth of this interface could be greater, particularly in areas drifted by the wind. Wind sculpting and some deeper drifts were observed at mid-elevations, but no slabs were triggered. While the recent storm snow was generally light and fluffy containing a few midstorm layers, about 5 inches above the MLK crust (base of the new storm snow) was the most interesting interface examined. It was here that the most consistent and planar breaks occurred during snowpack tests. As of Thursday night, we do not have any confirmed avalanches on this layer, but it bears watching and considering if you’re planning on stepping into consequential terrain on Friday. Prior to this most recent storm, a fairly poor bond to the MLK crust was reported and multiple avalanches were triggered.

Regioni coperte