Boletín de aludes

East Slopes Central

Northwest Avalanche Center
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Peligro de aludes

Thu
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
3 · Notable
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Desactualizado: este boletín caducó 6 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Dangerous avalanche conditions remain on the heels of a major storm and avalanche cycle. Avoid large slopes 35 degrees and steeper, especially where recent westerly winds formed thick slabs. You may still be able to trigger unsurvivable deep slab avalanches.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    2

    Very strong west winds created thicker and more reactive slabs in any exposed, open slopes. Wind slabs alone could be large and destructive. In wind-sheltered terrain, storm slabs and wet loose avalanches could be easy to trigger. Avalanches in the storm snow could step down, resulting in unsurvivable deep slab avalanches. Avoid wind-loaded, leeward slopes near and above treeline. Stay off of, and out from underneath large slopes steeper than 35 degrees and avalanche runout zones.

    (2/19/2021) An example of wind loading at 4,000ft on Blewett Pass from Friday.

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    3–4

    These avalanches are unsurvivable and it's not possible to manage them. The best way to stay safe is to avoid large avalanche paths and overhead start zones. Avoid traveling below large slopes 35 degrees and steeper. Most of these avalanches originated from slopes 5,000ft and higher.

    Wednesday will be the first time we'll have seen ridge tops since at least the 16th, if not longer. Even professional experts are unsure of the current likelihood of Deep Persistent Slab avalanches. We do know that many natural avalanches ran on Sunday and Monday big enough to destroy cars and houses. Some of these ran 2-3,000ft to the valley floor and involved a weak layer of facets and a crust that was buried in mid-January. While Solar aspects appear to have been especially problematic, we know deeps slabs have also run on north and northwest aspects. With the storm just barely behind us, the threat of these very dangerous avalanches remains.

    (2/20/2021) A persistent slab avalanche was triggered on a nice, sunny day on a southeast aspect at 6,100ft in the Wenatchee Range near Colockum on Saturday. Luckily all the riders escaped and were ok. The slide (D2) appeared to have run on the mid-January crust.

Avalanche Discussion

Dangerous conditions and challenging weather have prevented observers from gathering information from this zone. We believe the peak of avalanche activity occurred on the 22nd. Observers reported large to very large avalanches on the SE aspects of Dirty Face and Round mountains. Wet Loose avalanches were reported in Tumwater Canyon on the 21st and 23rd. Most were size D1-2 with one D2.5. 

The following are observations from nearby Stevens Pass on Monday, the 22nd: In the Scenic area, guides reported size D3 natural avalanches running on the mid-January weak layer 3-10ft deep on W-N aspects. Natural avalanches ran on SE and SW aspects of the Tunnel Creek area to D2.5. WSDOT triggered a very large size D3 in one of the Old Faithful paths on a SW aspect below treeline. Observers reported natural avalanches to size D3 on a SE aspect of Lichtenberg Mtn as well as a D4 sized avalanche on a SE aspect of Rock Mountain in Schilling's creek. This avalanche broke many mature trees and deposited debris 40 feet high near Highway 2. 

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