Lawinenlagebericht

Stevens Pass

Northwest Avalanche Center
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Lawinengefahr

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

Small wet loose slides could become common on most slopes with warmer temperatures and sunshine. Chances remain to trigger a small, soft wind slab at higher elevations. Isolated deeper slabs continue to be reported from around the region, a clue that deeper layers at upper elevation may not be trustworthy quite yet.

Lawinenprobleme

  • Loose Wet

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

    4-6" of new snow resting on a sun crust makes a good recipe for loose wet avalanches.  Loose slides could occur naturally as the snow surface becomes moist with sunshine and daytime warming. Watch for roller balls and tree bombs as indicators that the snow is becoming moist. For the most part, these should be small, but in larger terrain they could entrain more snow than you'd want to mess with. You'll want to exercise caution near terrain traps like slopes above cliff bands or tight gullies where a slide could push you somewhere with increased consequences.

    (3/15/2023)

    Large wet loose avalanche that likely ran on March 13 or 14th.

    Photo: Matt Primomo

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1.5–3

    Small, soft slab avalanches could remain possible on Wednesday. You're likely to find these at upper elevation where more snow fell, and wind transport was active through the day on Tuesday. Look for drifting patterns and textures, and feel for slightly stiffer snow as you gain elevation. Look for signs of instability like cracking  and use small test slopes to check for instability.  Steer around drifts on steep and/or unsupported wind drifted features.

    The monsters in the basement warrant a special note. A few isolated, but very deep (up to 10ft deep) slabs have been observed over the past week. We suspect many of these have run on a crust from mid February. While the chances of actually triggering one of these is probably very small, large loads like snowmobiles or big cornice failures could potentially still do it. If any very large slides did occur, they would run much further than you might expect, so best to add in lots of buffer room away from large steep slopes while your out in the mountains.

    (3/15/2023)

    NE aspect at appx 5,300ft east of the Swath. This pocket was estimated to have occurred March 10th or 11th.

    Photo: Matt Primomo

Avalanche Discussion

Expect sun and warmer temperatures to become one of the main influencers of our avalanche conditions over the next few days. Temperatures are on the rise for Wednesday, and sun should do its thing to most aspects except for northerlies. On Wednesday I found up to 6" of new snow resting on a supportable sun crust on SE to SW aspects on Lichtenberg. Wind had drifted some snow on the exposed shoulder, but drifts were soft I didn't observe much cracking. Observers reported natural wet avalanches to size D2 on steep, sunny slopes and some cracking in wind-stiffened snow near and above treeline on Tuesday. Another 6-8" of snow fell on Monday with snow level up to 3,500ft, and Brooke and I observed a natural wet loose cycle occuring during the day. Some notable large slides occurred off the south side of Lichtenberg and Rock Mountain. 

On Saturday, observers reported a couple of very notable avalanches. A very large D3 natural avalanche occurred on the north side of Rock Mtn, likely on the 10th.  The crown was at 6,750ft, NE-NW, estimated at 6-10ft deep, 500ft wide and it ran approximately 1800 vertical feet. Two similar D3 avalanches were reported above treeline on Cannon Mtn in the neighboring East Central zone. These were suspected to have run on the Valentines Day Crust, buried in mid February. Between 2/28-3/6 we received a few earlier reports of triggered avalanches that likely ran on this crust as well. On March 7th, I dug a profile on an adjacent slope to one of these slides on a SSW aspect below Skyline Lake. This crust is now 3-6 feet below the surface and avalanches on it would be difficult to trigger, but would be very large.

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