Bulletin d’avalanche

Stevens Pass

Northwest Avalanche Center
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Danger d’avalanche

Sun
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 3 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Heads up! Daytime warming should take hold of the snow and avalanche conditions this weekend, increasing the chances for hazards like wet loose avalanches, cornice fall, and very large deep slab avalanches. The danger is lower early in the day, but should rise as the sun and warm temperatures melt snow surfaces. Keep timing and overhead hazards in mind, and be ready to adjust your tour plan as temperatures heat up. 

Problèmes avalancheux

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Early in the day surfaces should be frozen and many crusts are now supportable. Expect east aspects to begin warming up first, and then south and west later in the day. Look for rollerballs, tree bombs, and feel for heavy wet snow as indicators that things are starting to happen. Slides may become large on steep or rocky slopes as the day progresses and warming continues to break down the crusts in the upper part of the snowpack. Use timing to your advantage, and be ready to steer clear of certain steep slopes.

    (3/15/2023)

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

    Photo: Matt Primomo

  • Cornices

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1.5–2.5

    Cornices are beginning to creep and peel away from ridges. Stay out from underneath any large cornices near ridgelines, as they tend to surprise people every season by breaking back further than expected with close calls and accidents.

    A few isolated, but very deep (up to 10ft deep) slabs have been observed over the past week. While triggering one of these is not likely, large loads like snowmobiles, big cornice failures, or perhaps a warming event like this one could increase the chances of seeing them release. 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 well away from large steep slopes while your out in the mountains this weekend.

    (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 the main influencer of our snow and avalanche conditions this weekend. Temperatures are on the rise, and sun should melt snow surfaces on all aspects except for northerlies. On Friday I went out to Alpine Lakes High Camp just east of the zone, and saw a round of small wet loose slides occurring on east and south aspects. It felt quite wintry in the morning with surface hoar growth in many areas, but by the afternoon was beginning to feel like spring. I found the Valentines Day Crust down about 3ft on a NE aspect at 5,600ft, and weak snow underneath it all the way to the MLK Crust. This may have been the structure that some of the deep slab avalanches noted below occurred on.

An impressive deep slab avalanche was noted from the West Face of North Chiwaukum on Thursday. This may have run  during a similar time frame as the others below on the 10th or 11th. 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 from NW aspectsabove 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 but we haven't been to a crown to confirm. Between 2/28-3/6 we received reports of triggered avalanches that likely ran on the Valentines Day crust. 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 triggering of an avalanche on it would be difficult, but could be very large and destructive.

Régions couvertes