Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
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Pericolo valanghe

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2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
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In sintesi

Avalanche hazard could increase throughout the day on Friday and should be highest during periods of heavy precipitation or strong winds. Temperatures have fluctuated recently and you could find varied avalanche problems if the snow surface is wet and sticky. When in doubt, avoid terrain features over 35 degrees where triggering an avalanche is more likely.

Problemi valanghivi

  • Wind Slabs

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

    Winds should ramp up significantly on Friday afternoon, possibly thickening existing slabs or building fresh ones at upper elevations. These unstable pockets of snow should be larger and possibly more reactive as you ascend in elevation and will remain the most likely location for you to trigger an avalanche. Take special care on leeward slopes near ridgelines, on convex rollovers, or near rocky features such as confined gullies and the base of cliffs where wind sifted snow likes to accumulate. Actively blowing snow will be the easiest indicator of where new slabs are developing, but if the winds are calm you can look for smooth pillow-like piles of snow or other visual clues such as textured surfaces to help you identify wind-loaded features to avoid. 

    (2/1/2022)

    Actively blowing snow will be the easiest indicator that fresh Wind Slabs may be forming on Friday.

    Photo: Dallas Glass

  • Storm Slabs

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

    Misty conditions on Thursday allowed the snow surface to dampen and create heavy snow over weaker snow, which is a good setup for Storm Slabs. You can check for this by digging in the snow with your hand or shovel to see if the snowpack is “upside-down” above the Late January Crust. Even plunging your foot or a pole into undisturbed snow can give you a feel for if there is light snow underneath a heavier surface layer. If you find this setup, seek out small test slopes or use upslope tests as you travel to give you an indication of how the snow is reacting to your weight. If you find that the snow is failing in blocks or there is heavy snow over weak snow, you should be leery of terrain features over 35 degrees where avalanches like to initiate. 

    Additionally, if the snow surface is damp and you see rollerballs and pinwheels, start thinking about small Wet Loose avalanches on steeper slopes. 

    (2/1/2022)

    Quick hand pits can help you identify an "upside-down" snowpack or slab potential. This test consistently failed on a density change in the storm snow about 12-15" below the surface (4" above the 1/30 crust).

    Photo: Dallas Glass

Avalanche Discussion

Thursday’s storm came in a bit warmer than expected and delivered a bit less water and wind than we had anticipated. As mentioned above, this resulted in some soggy conditions and a general “thickening” of the upper layers of the snowpack. Alpental Pro Patrol reported they were able to initiate small avalanches in the top couple inches of the snow once it became wetted and more cohesive. Additionally, recreationalists reported seeing some pinwheels and rollerballs as temperatures warmed. On Friday, you could find a small crust on the surface in areas where the snowpack was wetted. If this crust breaks down, similar conditions to Thursday should exist until the next wave of storms arrives later in the afternoon. If it doesn't break down, it could act as a sliding surface for any new snow. As this storm approaches, winds should increase significantly meaning hazard could increase throughout the day.

We expect any avalanche activity on Friday to occur above the Late January Crust. This prominent snowpack marker can be easily found roughly a foot below the surface, but depth will vary greatly based on elevation and exposure to wind. Near this interface, a weak "facet-crust sandwich" structure has been identified in some areas of the zone. We believe this setup is predominantly found on slopes that contain a northerly tilt (NE-N-NW) and at this point no known avalanches have occurred on this layer. We will be monitoring as we incrementally increase the load above it to see when it may reach its tipping point. If avalanches start to fail on these persistent grain types, they could act in surprising ways by breaking above you or spanning farther distances than you may be used to.

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