Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

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

Another storm will bring moderate snowfall and strong winds. Monitor the amount of new snow as you travel and avoid steep, wind loaded slopes.  Unusual avalanche activity in upper elevation terrain warrants more caution through the weekend. 

Problemi valanghivi

  • Storm Slabs

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

    The avalanches you are most likely to see Friday are storm and wind slabs formed by snowfall and strong winds overnight. Fluctuations in snow level and temperature could create alternating stronger and weaker layers within the new snow on all aspects. These could be quite reactive if snowfall meets or exceeds what is expected. 

    Fresh slabs don't take special tools to observe. Use small test slopes to gauge reactivity and look for new natural or human triggered avalanches. Hand pits might show a stronger layer sliding easily over a weaker layer below. You are more likely to trigger an avalanche in downwind terrain where the wind drops new snow into thicker and/or more sensitive slabs.

    Also, be alert for signs of instability and small wet avalanches with rain or during sun breaks.  Rain to 5000' Thursday initiated a round of wet loose avalanches. Fresh snow tomorrow could see the same fate with enough warming.

    (2/7/2023)

    Example of fresh slab skier triggered during a storm.  Steep terrain and new snow equal a shallow but very easy to trigger avalanche.

    Photo: Alpental Pro Patrol

Avalanche Discussion

There are also avalanches out there you are less likely to see but more likely to ruin your day. Large human triggered avalanches were reported from Canyon Creek and Schriebers Meadow on Wednesday. They were not typical wind slabs but did occur in obviously wind loaded terrain. The layer thought to be responsible for these avalanches - facets combined with a melt freeze crust - is the same one suspected as behind the widespread avalanche cycle during the storm. In some places, a layer of graupel is found instead of weak faceted grains.

There was lots of variability in the snowpack prior to the big storm. Some places were scoured down to near the MLK crust while others sported a stiff wind slab. Some areas accumulated new snow which in turn faceted during cold temperatures. The storm also produced different patterns of natural avalanche activity. The backcountry terrain around Mt. Baker Ski Area saw a widespread avalanche cycle while other areas saw less natural activity.

It would be nice to be able to pick out the pattern so we could avoid just the areas where this setup exists. So far it's above treeline, wind loaded terrain - not super helpful. Digging pits is great and adds to the big picture of how snowpack varies across the zone. Pits may or may not do much to help you gauge if the slope in front of you is good to go. If you head into this sort of terrain you are just assuming more risk than usual.

 

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