Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
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Pericolo valanghe

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Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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In sintesi

Conditions on Sunday should be primed for human-triggered avalanches on slopes 35 degrees and steeper. Make conservative terrain choices and give the snowpack the time it needs to adjust to the recent load.

Problemi valanghivi

  • Storm Slabs

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

    Take a look at the recent storm snow on Sunday to see how it has bonded to the old snow surface and for layers of concern in the upper snowpack. Reports from Saturday indicate that the snow is not well bonded in some areas of the zone and that interstorm layers were reactive. Observations are limited from upper elevations due to the ferocity of the storm, but you could find that slabs are thicker and possibly more reactive as you ascend in elevation or in wind-prone areas. You can use hand pits or test slopes as you travel as a quick reference for how the upper layers of the snowpack are bonded. Uptrack tests can easily highlight snow breaking off in blocks or shooting cracks to indicate slab potential. If you see these signs or find heavy snow over weak snow, avoid slopes over 35 degrees.

    (12/18/2021)

    This slab was intentionally triggered by a skier on Alpental Pro Patrol and failed at the base of the recent storm snow on 12/18. The slab is found at the base of a cliff where wind drifted snow likes to accumulate and slabs are often easier to trigger. 

    Photo: Alpental Pro Patrol

Avalanche Discussion

The snowpack just took on a lot of water on Saturday and will need some time to adjust to this new load. The adjustment started during the height of the storm on Saturday but should continue into Sunday. Alpental Pro Patrol reported both skier triggered and natural avalanches at the base of the recent storm snow on Saturday. Across the street, ski tourers in the Commonwealth drainage reported natural avalanches that covered the PCT - a common travel route for skiers and winter hikers. These avalanches are red-flag signs of instability that should not be ignored. 

Although we anticipate natural avalanche activity to taper on Sunday, the snowpack contains touchy storm slabs and should be primed for human triggers. Observations from multiple professionals in the zone indicate that a layer ~15cm below the surface or the new/old snow interface (~25cm below the surface) is the culprit of recent avalanches and should be your first targets when inspecting the snow for instability. A new freezing rain crust should exist in the upper snowpack, with the possibility of some weak snow near it. This could be another potential point of failure that you need to be aware of and test before committing to avalanche terrain. Avalanches that fail on this layer could break in surprising ways, so don’t be caught off guard. 

The snowpack at lower elevations may have eluded the rain in some areas of the zone,  but that doesn’t mean that it didn’t take a bit of a beating. Although you could find locally lower avalanche hazard at these elevations, especially on the Western edge of the zone, open creeks or shallowly buried rocks and stumps still exist as we continue to build our early season snowpack.

Regioni coperte