Bulletin d’avalanche

East Slopes North

Northwest Avalanche Center
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Danger d’avalanche

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

Points saillants

In the wake of an intense storm, you can trigger avalanches in the new snow. The most dangerous areas will be leeward sides of ridges where winds drifted deep slabs. For Thursday, winds will subside and you can expect filtered sun with a chance for light precipitation. 

Problèmes avalancheux

  • Storm Slabs

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

    With the massive amount of new snow, it's a good idea to limit your exposure to large steep slopes and avalanche runouts. Avalanches could take a variety of forms and sizes depending on where you travel. In wind-sheltered terrain, you may still be able to trigger storm slab avalanches within the recent snow. Strong winds drifted deeper slabs below cliffs and on leeward sides of ridges and wind-exposed features. Here, avalanches could easily be big enough to bury and kill you.

    On shaded west through north through east aspects, there's a chance for very large avalanches to break widely and run on weak snow adjacent to a crust, now approximately 3-4 feet below the surface. At low elevations, east of Mazama, there's now enough snow for consequential avalanches. If you're traveling in these areas, watch for signs of instability like collapses and cracks. Wherever you travel, be ready to stick to slopes less than 35 degrees. 

    (2/2/2024)

    An example of deep crown of an avalanche (D2.5) that occurred last season during a similarly warm storm. Blue Lake Peak, 7,600ft, N.

    Photo: Chris Bartram

Avalanche Discussion

A major storm impacted the region Tuesday night into Wednesday and brought significant snow to all areas including low-elevation terrain and the eastern mountains. Temperatures stayed cold and precipitation was mostly dry snow. Some warming of snow surfaces likely occurred west of Washington Pass and at some low elevations.

Snow water storm totals from weather stations likely only tell part of the story. Rainy Pass: 3.4" SWE, WA Pass:  1.7" SWE Mazama 1.7" SWE. An observer in Mazama reported storm snow totals of 36" and wet loose avalanches. On Wednesday, few people were able to venture into the mountains. Observers near Frost Lake reported collapsing whumpfs and plumes of blowing snow on the ridge of Oval Mountain.

On Tuesday, observers went to Rainy Pass and found minimal wind slab conditions at middle elevations. They noted some weak snow above the 12/7 crust. While the crust is now deep, (best guesses are 3-5 feet) it's worth taking time to investigate it. If you experience whumpfing collapses, stick to low-angle slopes. On Sunday, an NWAC forecaster went to upper elevations of Blue Lake Peak. On shaded slopes, the 12/7 crust was buried 10-16 inches deep and had weak, faceted snow on either side of it. Near Rainy Pass, the 12/7 crust is more robust, while it's thin and brittle on shaded slopes near and east of Washington Pass. 

You can contribute to the avalanche forecast. Please let us know what you see in the mountains by submitting an observation. 

Régions couvertes