Lawinenlagebericht

Stevens Pass

Northwest Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
4 · Gross
Waldgrenze
4 · Gross
Unterhalb
4 · Gross
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Kernpunkte

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. 

Lawinenprobleme

  • Deep Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    3–4

    Very large and historic avalanches could run into low elevation terrain. Avalanches this big haven't 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 terrain and paths that could start 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 5-7 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.

     

    (2/22/2021) On the 22nd, a very large natural avalanche broke mature trees and deposited massive debris near Highway 2, east of Stevens Pass. The avalanche ran on a SE aspect of Rock Mountain. Photo: Harlan Shepard

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Very Likely
    Größe
    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.

    (1/28/2021) An example of wind slab on Tye Peak. Photo: Marc Simonpietri

Avalanche Discussion

Numerous very large natural avalanches ran on southerly slopes on Monday. Slides at size D3 to D4 ran on a SE aspect of Tunnel Creek area, on a SE aspect of Rock Mountain, and on a SE aspect Dirty Face Mtn, near Lake Wenatchee. US Highway 2, Stevens Pass has been closed multiple times due to avalanche hazard in the past 72 hours. Both natural and controlled avalanches hit the highway on Monday.

On Monday, rain fell on previously dry snow to about 4,500ft. As of 5p on Monday, the Schmidt Haus weather station has registered 5" of water equivalent since the 20th and about 9" of water in 10 days. Prior to the 21st, most precipitation fell as snow above 2,500ft. Expect another 1-2 feet of light, dry snow by Tuesday evening. 

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