Lawinenlagebericht

East Slopes Central

Northwest Avalanche Center
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Lawinengefahr

Fri
Hochgebirge
2 · Mässig
Waldgrenze
1 · Gering
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 5 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Deep persistent slabs are unlikely, but not impossible. Unstable areas of shallow wind slab may still be found on high elevation, shaded slopes. These hazards are most likely in very steep, and unsupported terrain in the shade.

Lawinenprobleme

  • Deep Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    3

    Observers continue to find sudden results with snowpack tests on a layer of faceted grains above or within the Mid-January crust. Avalanches have been 3-8ft deep, and the crowns generally encompass most if not all of the terrain features. Higher elevation shaded, and heavily wind-loaded, or unsupported slopes may be the most likely areas one of these could still happen. Steep slopes that face the sun may have a thick melt-freeze crust near the surface. If this is the case, these may not be a concern on those slopes. 

    Be intentional about where and how you travel, and be sure to discuss the low probability but high consequences with your partners. Before venturing into or under big terrain features, ask yourself, what would a very large avalanche in this terrain look like? How far could it travel?

    Cornices are large and sagging in some areas, keep on the lookout for these and stay well away from them. If cornices fall, they could trigger very large deep persistent slab avalanches.

    (3/3/2021) This avalanche likely occurred around February 26. ENE aspect at 7,300ft west of Cashmere Mountain.

Avalanche Discussion

With the anticipated warm temperatures, its' worth keeping wet avalanches in mind. Most solar aspects have well-developed crust making these avalanches unlikely. Near the Cascade crest, you may find some older, shallow wind slabs that would now be difficult to trigger. 

We don't have any new observations of deep slab avalanches since March 1, however, the snowpack structure needed to make them can still be found in many areas. We currently have a wide range of conditions between mountains near the Cascade Crest and further east. The slab that sits over this weak layer ranges dramatically from around 8ft thick near the crest to less than 3ft in the eastern Wenatchee Mountains. We've pulled the Deep Persistent Slab problem from other zones in the Central Cascades, but there is just too much variability and not enough confidence to do that in the very large East Central Zone.

Numerous deep and very wide avalanches (Many D3-3.5's, some size D4's)  ran between February 21st and March 1st in the mountains near the crest, and some deeper slabs were reported from the Wenatchee Range. In the northern end of the zone, near Holden, the mid-January weak layer doesn't appear to be a concern anymore.

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