Bulletin d’avalanche

East Slopes Central

Northwest Avalanche Center
Voir sur la carte

Danger d’avalanche

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

Points saillants

It's a low likelihood, high consequence situation in the mountains right now. A large trigger like a cornice fall, snowmobile, or group of people in the wrong spot could trigger a very large and destructive avalanche that runs on old facets and crusts from December. Stick to lower angle and well supported slopes, and give yourself a wide buffer from bigger terrain for the time being. 

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–2.5

    The snowpack is resting on a weak foundation. A layer of facets and decomposed crusts that were buried around the Solstice have continued to cause avalanches for a couple of weeks.Persistent slabs are a tricky problem, often leading to a false sense of security with no apparent signs of instability, such as collapses or shooting cracks. A cornice fall, small surface avalanche, or snowmobile could be the trigger for one of these. Maybe it's not the first skier or rider on the slope, but it could be the second or third. A good strategy is patience and conservative travel choices. Choose well supported and lower angle terrain. Identify large, steep terrain features steer away from. Stop and regroup in safer areas, giving yourself wide safety buffers away from potential runout zones. 

    This problem is not limited to only the Wenatchee Mountains, but it's where all the recent reported activity has taken place. Further west the weak structure still exists, it's just more deeply buried and may be more difficult to trigger. If you got unlucky, or a cornice drops, a 2-4ft deep avalanche could result, and it would be surprisingly destructive. 

    (1/24/2024)

    Very large hard slab triggered with explosives at Mission Ridge.

    Photo: Mission Ridge Ski Patrol

Avalanche Discussion

Light new snow is expected on Thursday. On Wednesday the mountains picked up anywhere from 2-6" of new snow. With the reent warming, you're likely to find a couple of thin crusts in the upper snowpack. These top a hefty couple feet of storm snow from the month of January. With the new snow comes potential for small sluffs. These loose dry slides could run off steep cliffy areas during periods of heavier snowfall rates, and could be triggered on steep slopes. Later in the day at lower elevations or in the sun, look for rollerballs and feel for moistning snow as a clue to potential wet loose slides. At upper elevations, light winds could drift the new snow into small wind slab pockets. Look for slightly textured surfaces and cracking as a sign of these near ridgetops.

The Solstice Crust/Facet Complex in the Wenatchee Mountains has been active since late December and has continued to produce avalanches. Mission Ridge Ski Patrol triggered some very large (D3), hard slab avalanches on Wednesday with large explosive work. These were from north and east facing slopes below corniced ridgeline in the upper 6,000ft range. Human triggered avalanches on this persistent weak layer have occurred on Jan 6th, 12th, 15th, 19th, and 20th. While these avalanches have primarily occurred in wind-loaded terrain, we can't rule out avalanches in sheltered areas as there is a lot of storm snow above this layer.

I was out on the 22nd and 21st in the far western edge and the eastern edge of the zone. Although the snowpacks ranged in depth from 150cm in the upper Icicle to only 100cm in the Blewett Pass area, there were certain commonalities that are worth discussing. First, there is a substantial amount of new snow since January began (2-3ft). Second, we could identify a weak structure near the base of the snowpack that consisted of faceted grains over and often beneath a weak, decomposed crust (2-3ft down). Third, snowpack tests showed the potential for avalanches to propagate on this layer in both locations.

If you get out, let us know what you see by submitting a public observation!

Régions couvertes