Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
Vedi sulla mappa

Pericolo valanghe

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

In sintesi

We're in for a stormy couple of days at Snoqualmie Pass. Begin to think about slab avalanches anywhere you find over 6 inches of new snow. They’ll be easier to trigger on convex features or in wind-loaded pockets over 35 degrees.

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    As snow piles up Wednesday night and Thursday, you could encounter small storm slabs at mid and upper elevations. The higher you ascend, the larger they should be. Use small test slopes and uptrack tests to determine how the new snow is reacting to your weight. If you find heavy snow over weaker snow, see shooting cracks, or blocks of snow failing in your tests, default to lower-angled terrain.

    Slabs should be thicker and possibly more reactive in wind-exposed areas than in sheltered terrain. In isolated locations, slabs could break in surprising ways - running on the 12/30 crust or stepping down to deeper layers. See below for more details.

    (12/8/2023)

    Hand pits are a great way to look at the recent storm snow. Look for strong over weak layers and places it fails easily. 

    Photo: Andy Harrington

Avalanche Discussion

Backcountry travelers on Wednesday were greeted by new snow. At lower elevations, slightly warming temperatures helped consolidate the roughly 3-4 inches into our already strong but thin snowpack. At upper elevations, Alpental Pro Patrol reported shallow wind slabs that failed easily and ran on the 12/30 crust. Avalanche professionals in the Alpental Valley reported up to 7 inches of new snow that failed easily in snowpack tests on the 1/2 interface. They also noted failures on some of our deeper layers of concern.

The next few days should deliver snowfall and a lot of excitement for winter enthusiasts. It might also bring snowpack issues to the forefront that we haven’t had to contend with for a while. Here’s some information on potential weak points, starting with the deepest:

  • 12/22 interface: The deepest layer of concern. It is roughly 1-1.5 feet deep. This crust/facet complex has been propagating in large column tests and has had our eye for about a week now. It could produce the largest avalanches and they could span far distances.
  • 12/25 crust: The next significant crust above the 12/22 complex. This layer was producing planar failures for professionals on Wednesday. It was not propagating in large column tests. 
  • 12/30 crust: Closest easily identifiable crust to the surface. It should be the sliding surface for most avalanches in the coming days. 
  • 1/2 interface: A layer of buried surface hoar may exist an inch or two above the 12/30. Where it exists, avalanches breaking on this layer could span far distances or wrap terrain features. There also might be near-surface facets around this depth in some locations. Avalanche professionals received easy failures on this layer on Wednesday using tilt and compression tests.

Snow is expected to fall Wednesday night into Thursday. A convergence zone may clip the zone and enhance snowfall amounts during the day. If we exceed our forecasted water numbers, dangerous avalanche conditions may develop at upper elevations. Your most significant concern at lower elevations should continue to be travel hazards.

Regioni coperte