Lawinenlagebericht

Snoqualmie Pass

Northwest Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Kernpunkte

Just because the storm is wrapping up and the sun is coming out doesn’t mean everything is good to go. You’ll need to spend some time looking at the new snow for potential failure points. Triggering a slab avalanche will be more likely on steep slopes over 35 degrees or in wind-loaded terrain.

Lawinenprobleme

  • Storm Slabs

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

    Snowfall should cease by Tuesday morning after nearly constant waves of precipitation have impacted the zone since Sunday evening. Expect to encounter unstable slabs on steep slopes over 35 degrees or in wind-loaded areas near ridgelines and rocky terrain. Larger and potentially more reactive slabs will exist as you ascend in elevation. Using uptrack tests or small test slopes can help you determine how easily and deeply the new snow is failing. Digging quick hand pits to check the initial bond, determine if the snow came in “upside down” (heavy snow over weaker snow), and locate interstorm layers of concern can further help you identify slab potential. If you notice a poor bond or that snow is failing as blocks during your tests, avoid slopes over 35 degrees.

    (2/7/2023)

    Example of slabs triggered during a storm earlier this week.  Steep terrain, fresh snow, and wind-loading can all combine to create avalanches in new snow layers.

    Photo: Alpental Pro Patrol

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–1.5

    With cold dry snow in place and the sun expected to make an appearance as this storm wraps up, we can’t rule out solar-induced loose avalanches on Tuesday. As is typically the case, it remains to be seen if this one plays out as a battle between cold temperatures and sunny skies unfolds. If sunshine wins, you could see avalanches that start at a point and fan out as they move downhill. They’ll be most likely on steep slopes over 35 degrees that see direct sunshine and will be preceded by rollerballs or pinwheels. You may see them initiated by snow shedding from trees or rocks even if the snow surface isn’t yet wet and sticky - manifesting more like a Dry Loose. Regardless of the moisture content, their behavior and management remain the same. If you notice the signs, don’t get tripped up by one in consequential terrain and you can always head for shadier slopes to avoid them altogether.

    (2/13/2023)

    A small loose avalanche triggered by snow shedding from trees.

    Photo: Dallas Glass

Avalanche Discussion

As of Monday evening, a convergence zone has taken aim at Snoqualmie Pass and is currently delivering snow showers at high precipitation rates. These rates may not be sustainable, but the storm will linger through the evening hours and is expected to deliver another 6-12” of snow to the Pass before quieter weather takes over on Tuesday morning. 

Observations from Monday are limited, but avalanche professionals in the Kendall area midday reported increasing snow depths as they ascended toward ridgecrest [3-4 inches at lower elevations increased to 6-8 inches around 2:00pm]. The initial bond of the new snow was reportedly good as the underlying crust remained wet and sticky from Sunday night’s rain. The new snow contained plenty of graupel and other forms of rimed particles as convective showers rolled in and out of the zone. No new avalanches have been reported.

On Tuesday, we anticipate most avalanches to occur within or at the base of the new storm snow. That layer of graupel could come into play in some areas, resulting in a few surprising or widely breaking avalanches. Although not expected, we wouldn’t be shocked to hear of a few avalanches breaking into deeper layers. Anything deeper than the 2/3 interface would be a surprise for sure.

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