Lawinenlagebericht

Snoqualmie Pass

Northwest Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
Open full map
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Kernpunkte

Use visual clues such as cracking of the surface or pillow-like drifts to identify wind-loaded features where triggering an avalanche is more likely. Consider the possibility of very large avalanches on large open slopes and talk with your partners about your travel plans and acceptable level of risk. It should be a bit warmer, but bring extra layers to prepare for chilly temps.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    The wind was ripping out of the East on Saturday, leaving behind wind slabs for you to manage on Sunday. They could exist on aspects you’re not used to or further down in the terrain due to cross-loading. Visual clues such as fresh cornices, hollow-feeling snow, or textured surfaces can indicate where this problem exists. Look for them on leeward slopes near ridgelines, the base of cliffs, or the sides of chutes/gullies. It's been a while since anyone has been to upper elevations, but slabs are likely larger and possibly more reactive in these areas. 

    We've had several windy days this week and plenty of low-density snow available for transport. With temperatures this cold, these slabs may not heal as quickly as you're used to. Feel for density changes as you travel to help identify older slabs that could still be reactive. 

    (1/11/2024)

    Small avalanches were easily triggered by skiers on Thursday in the Alpental Valley.

    Photo: Andy Harrington

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    2–3

    It's well understood that we have a poor snowpack structure roughly 4 feet below the surface at middle and upper elevations. The 12/30 and Solstice Crusts continue to produce failures in snowpack tests. That sets the stage for us to know the size and distribution of any potential avalanche on these layers. What we're missing from the equation is the sensitivity to triggers.

    Since this past week has been so stormy, getting information on whether we already had a cycle on these layers has been challenging. And with so much new snow, any crowns are already filled back in. We had one notable avalanche this week suspected on these layers. It was triggered by explosives at Alpental on Wednesday (1/10). These layers have been more active in the neighboring West South and East Central zones.

    The current thinking is that a more significant trigger may be needed to activate these layers, such as a step-down avalanche or cornice fall. We've been known to be wrong, however. So realize the risk as you travel, and if you want to minimize your exposure, stay off big open slopes where triggering this layer would likely result in an unsurvivable avalanche. 

    (1/10/2024)

    This very large avalanche released remotely from nearby explosive placement during avalanche control at Alpental. It is an indication that deeply buried weak layers could still be active. 

    Photo: Alpental Ski Patrol

Avalanche Discussion

We should be in line for a warming trend on Sunday as easterly winds ease and ambient air temperatures moderate. It will still be chilly, however. So, continue bringing extra layers and other precautions to help you stay warm out there.

The Pass has received over 4 feet of snow in the past week, often accompanied by strong winds. These stormy conditions have resulted in multiple rounds of avalanches. Wind slabs, storm slabs, dry loose, and the more dangerous persistent slabs have all been reported. 

Observations from Saturday are limited. The frigid temperatures may have something to do with that. They fell well below freezing without the help of the icy east winds. Brave backcountry travelers reported plenty of wind-effect and cracking, even down in the trees, and the potential for small avalanches. A shallowly buried layer of graupel still exists in the upper snowpack.

Even though we downgraded the likelihood of triggering a persistent slab on Sunday, don't assume it's open season out there. We are operating with a high level of uncertainty surrounding that problem. You could travel all day and not see any signs of instability. We also wouldn't be surprised if a D3 avalanche occurred. We're living in the "scary moderate" world now and it's not a fun place to be. Consider minimizing your exposure by sticking to smaller slopes and being aware of what's above you. 

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