Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Wed
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
4 · Forte
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In sintesi

Very dangerous avalanche conditions continue with strong west wind, cold temperatures, and ongoing snow. Very large avalanches could run from above into lower elevation terrain. This could be another day to avoid backcountry travel. Continue to stay far away from and well out from under open slopes steeper than 30 degrees. 

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    3–4

    Very large and historic avalanches could run into low elevation terrain. Avalanches this big may not have occurred in this zone in many years. These avalanches are unsurvivable and it's not possible to manage them. The best way to stay safe is to avoid backcountry travel. If you choose to travel in the mountains, you must be able to avoid avalanche paths and terrain that could be over a thousand feet above you. Even where little snow cover exists at low elevation, it's possible that natural avalanches could come from far above. 

    We haven't seen or been to the ridge tops in many days, if not weeks. Even professional experts are unsure of the current likelihood of Deep Persistent Slab avalanches. We do know that on Monday natural avalanches were at least big enough to destroy a car and were running 2-3,000ft to the valley floor. We also know that prior to this storm, avalanches ran on a weak layer of facets and a crust that was buried in mid-January and is now 3-6 feet below the surface. It will be at least another day before we know the exact timing and extent of this avalanche cycle. With ongoing snow and wind, 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.

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    2–3

    The threat of deep slab avalanches trumps any storm-related avalanches. Very strong west winds will create thicker and more reactive slabs in any exposed, open slopes. Wind slabs alone could be very large and destructive. In wind-sheltered terrain, storm slabs and loose dry avalanches could run far and fast. Avalanches in the storm snow could step down, resulting in unsurvivable deep slab avalanches. Stay off of, and out from underneath slopes steeper than 30 degrees and avalanche runout zones.

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

Avalanche Discussion

On Monday, numerous very large natural avalanches were reported. Slides at size D3 to D4 ran on a SE aspect of Tunnel Creek near Stevens Pass, on a S aspect of Rock Mountain, on a SE aspect Dirty Face Mtn, and on Round Mountain. On Sunday, observers reported natural wet loose avalanches in Tumwater and widespread avalanches in the storm snow. 

On Monday, rain fell to about 4,500ft. You'll find rain-saturated snow at low elevations. Expect a quick shift to cold temperatures and light, dry snowfall. This will make for variable travel conditions below treeline. 

Regioni coperte