Lawinenlagebericht

Snoqualmie Pass

Northwest Avalanche Center
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Lawinengefahr

Thu
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

There’s a lot of new snow out there to manage and you could see it failing in a variety of ways on Wednesday. Be extra vigilant on features that are commonly wind-loaded such as convexities or confined gullies. On open steep slopes, you may encounter loose avalanches that could grow large given the right circumstances.

Lawinenprobleme

  • Wind Slabs

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

    There’s a lot of recent storm snow out there, but we’re anticipating the most likely location for you to trigger an avalanche on Wednesday will be on slopes where the wind has drifted snow into stiffer slabs. Look for Wind Slabs near ridgelines, on convex features, or near rocky terrain such as the base of cliffs or confined gullies. These slabs should be slightly stiffer than the surrounding low-density snow but likely won’t be Hard Slabs. Feel for changes in the consistency of the snow as you travel to help you identify the areas we’re concerned about. They could even be buried under a few inches of light fluffy snow. Wind-loaded features may look “pillow-like” or “fat” compared to the surrounding terrain and you might notice some textured surfaces nearby. If you suspect a slope to be wind-loaded, simply choose a simpler route to avoid it.

    (1/29/2023)

    Visual clues of wind-loading and Wind Slab development.

    Photo: Andy Harrington

  • Loose Wet

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

    Another mostly sunny day on Wednesday means solar-induced loose avalanches could again present a problem. Observations from Tuesday indicate that some slopes started to tip the scales, but we did not have a widespread loose cycle in the sunshine. Maybe we’ll see more activity on Wednesday. 

    These avalanches 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 could 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 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.

    (2/14/2023)

    Loose avalanches triggered by snow shedding from trees and rocks were observed on 2/14. Although triggered by sunshine, most of them involved dry snow.

    Photo: Andy Harrington

Avalanche Discussion

The convergence zone certainly delivered the snow at Snoqualmie Pass on Monday night. As Tuesday dawned blue, around 1 foot of snow was found at lower elevations. Storm accumulations quickly increased with elevation to as much as 2 feet of snow as found by NWAC forecasters and reported by Alpental Pro Patrol. 

During their morning mitigation efforts, slabs as deep as a foot were released via explosives by Alp’s Patrol. They also reported sensitive cornices and loose avalanches on steep slopes. NWAC forecasters further up the Alpental Valley found a large debris pile below Bryant Peak but could not determine where exactly it originated. They also noted countless small loose avalanches initiated from trees and rocks on steep slopes seeing direct sunshine. A few small Wind Slabs were triggered by avalanche professionals near ridgelines or on convex features. Avalanche professionals in the Kendall area reported minimal avalanche activity and less snow under tree cover (closer to 10 inches).

The snow was found to be generally right-side up and well bonded to the 2/13 interface. It was light and fluffy but started to get heavier due to solar input on sunny slopes by day’s end. On Wednesday, you could find a slight crust on the surface due to Tuesday’s sunshine. Shadier slopes will likely continue to harbor cold dry snow. With so much recent low-density snow, it can be a hazard in and of itself. Keep your partners in sight and be cognizant of tree wells. We anticipate any avalanche on Wednesday to be isolated to the newly fallen snow over the 2/13 interface so that's where you should focus your attention while performing your slope scale evaluations.

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