Lawinenlagebericht

Stevens Pass

Northwest Avalanche Center
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Lawinengefahr

Fri
Hochgebirge
2 · Mässig
Waldgrenze
1 · Gering
Unterhalb
1 · Gering
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Kernpunkte

Newly formed upper elevation wind slabs are where you're most likely to trigger an avalanche if you're going to trigger one on Thursday. Slabs will probably be small in size, but consider steering around high-consequence steep slopes if they have wind-drifted snow on them. If snowfall and wind amounts are different from what was forecasted, avalanche danger could be higher. 

Lawinenprobleme

  • Wind Slabs

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

    Recently formed wind slabs on leeward features are where you could probably trigger an avalanche on Thursday.  Search for clues of wind loading, indicated by rippled, textured surfaces or smooth, rounded pillows. Drifts tend to  form on leeward sides of features. These include beneath ridgelines, on convex rollovers, gully walls, or around rock outcroppings and cliffs. On Wednesday I traveled up to Big Chief Mountain (5800ft), where I found sustained moderate ridgeline winds, yet there was not much snow being transported. This is due to many snow surfaces having been previously wind affected or crusted over. In other locations and at higher elevations, more wind and snow available for transport may be developing larger slabs. 

    Approach steep, wind-affected slopes with caution, especially if they are in high consequence locations like around terrain traps. As most weaknesses are probably a foot or less in depth, you can do simple hand tests or skin track cuts in order to determine if a slab may be reactive from a nearby lower-angle area. If in doubt, steer around the steep, wind-loaded location. 

    (1/4/2023) Moderate easterly winds caused small amounts of transport on ridgelines on Wednesday. Identify loaded areas just below the slopes. Photo: Irene Henninger

Avalanche Discussion

Variable conditions may be your largest hazard on Thursday. At lower elevations, snow surfaces were described as "bulletproof yet skiable, with open creeks" at 3000ft, by forecaster Josh Hirshberg, who got a low elevation start for a field day just west of the pass on Wednesday. As you climb, you'll find crusts on steep, south-facing aspects at all elevations from a sunny day on Sunday. Many other treeless areas have various wind-affected snow surfaces.  On Wednesday I found a thin crust coating all treeless surfaces I traveled on, in the Big Chief Mountain area. This had formed during a misting event that occurred Tuesday, and Josh found at elevations up to 4200ft where he traveled, indicating presence in some, but not all areas in the zone. I also found thick rime coating ridgeline trees in exposed areas, which has been continuing to develop since Monday. 

December 23-27 the region experienced a stormy period with multiple rounds of heavier mixed precipitation. A crust, dubbed the Christmas Crust, is present from this period of mixed precipitation. It takes the form of a stout, translucent layer up to about 5000ft, and above that elevation you'll find opaque melt forms making up the crust. This crust can generally be found 1.5-2.5ft beneath the surface.

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