Lawinenlagebericht

Stevens Pass

Northwest Avalanche Center
Auf der Karte ansehen

Lawinengefahr

Wed
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Veraltet — dieser Lagebericht ist 6 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Dangerous avalanche conditions on Tuesday will require that you keep a large margin of terrain between you and slopes steeper than 35 degrees. You can trigger surprising avalanches that may break widely over terrain features, especially where the wind forms drifts of new snow. Warning signs of the avalanche danger include whumphing collapses, drifts of freshly blown snow, and a layer of weak, sugar-like snow over a crust about 10-20" below the surface.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2

    Avoid mid to upper elevation slopes steeper than 35 degrees where you find the wind forming fresh drifts and deeper areas of snow on the leeward side of ridges. Tuesday is a day to avoid wind loaded terrain. If triggered, any slope could break into older weak layers resulting in a very dangerous Persistent Slab avalanche (see below).  The most dangerous slopes will be near and above treeline where the wind drifts thicker slabs on an already weak snowpack. Pay attention to which slopes receive wind loading and the direction of the wind. Watch for blowing snow as an indicator. Moderate to strong winds will increase and shift from southwest to west through the day. Expect avalanches to be larger at higher slopes and to grow bigger as the day goes on. 

    (12/12/2020) Blowing snow captured in the foreground on the summit of Rock Mountain. Looking south towards the south peak. Will Govus photo

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2

    Persistent slab avalanches are very dangerous and can catch even the most experienced backcountry travelers by surprise. Put extra space between where you travel and any slopes 35 degrees and steeper. Stay far away from convex rollovers and steeper slopes. Do not stop or linger at the bottom of avalanche paths. Make sure to stop well out from under and off to the side of any terrain steep enough to avalanche. Use clues like broken trees, trees stripped of uphill branches, and a lack of vegetation to avoid the runout of avalanche paths. Until we know more about how the weak layer and slab are reacting, consider all avalanche terrain guilty until proven innocent. 

    Observers have reported a layer of weak facets (1.0-1.5mm) resting on a crust that formed in the past week. Near the top of Stevens Pass, you can find this week layer about 12-18 inches (30-50cm) below the surface. On Monday, observers in the Highway 2 corridor near Lost Lake and at the top of Stevens Pass reported snowpack tests that indicate propagation and large,  up to 100ft in diameter.

    (12/14/2020) Pointing out a layer of facets on a rain crust 37cm below the surface on a wind-loaded NE slope at 5040ft near Gemini Saddle. Snowpack tests indicated propagation.

Avalanche Discussion

By the end of Tuesday, you can expect 5-8" of snow accompanied by moderate to strong wind and warming temperatures. Below 4,000ft you may find moist snow surfaces and you may be able to trigger wet loose avalanches. Observers on Monday reported triggering a D1 wet loose avalanche on a northwest aspect at 5,000ft above Lake Susan Jane. The slide did not dig into deeper layers but observers found the December crust layer in snowpack tests. Expect shallow snow cover at low elevations with typical early season hazards like open creeks, stumps, and rocks. 

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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