Lawinenlagebericht

Stevens Pass

Northwest Avalanche Center
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Lawinengefahr

Fri
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Kernpunkte

On Thursday, you can trigger avalanches in recently fallen snow on slopes 35 degrees and steeper. The most dangerous slopes will be near and above treeline where avalanches may be bigger and easier to trigger. Watch for recent avalanches or test slopes that slide easily as signs that you should stick to lower-angle terrain.

Lawinenprobleme

  • Storm Slabs

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

    Storm slab avalanches will be larger and more dangerous near and above treeline. You could trigger avalanches within the new snow or at the interface of old and new snow. If you find snow that slides easily, stick to lower-angle slopes under 35 degrees. Avoid traveling on convex roll-overs and steep, unsupported slopes. Use extra caution in and around terrain traps, where any avalanche could have serious consequences.

    A total of 1.5-2 feet of snow could accumulate by midday Thursday. A key element will be warming temperatures Wednesday night into Thursday which could add necessary cohesion to the recent snow. Below the pass elevation, you may encounter heavier, moist snow and possibly small wet avalanches. Above treeline, you may encounter subtle drifting and stiffer, wind-affected snow. Cracking in the snow, sculpted drifts, and stiff feeling snow are all indicators. Avoid leeward wind-loaded slopes over 35 degrees. On any slope, you can use quick snow pits and small, inconsequential test slopes to check if the snow slides easily. Look for a potential poor bond at the new/old interface as well as within the top 2-3 feet. Observers reported some weak old snow surfaces including surface hoar buried on the 25th. 

    (12/28/2020) An example of a snowboarder-triggered avalanche in recent snow on Shuksan Arm near Mt Baker ski area (NE, 5400ft). Photo: Colin Wiseman

Avalanche Discussion

Over 10 inches of light, uncohesive snow piled up at Stevens Pass by the end of Wednesday. You can expect roughly that much more by midday Thursday. While most avalanches reported on Wednesday were loose dry point releases, it's worth noting that to the south at Snoqualmie Pass observers reported very reactive conditions with widely propagating slab avalanches. 

A stout crust formed on December 21st and is now 2 feet or more below the surface. There have been reports of weak snow grains immediately above the crust. Keep an eye on this interface as the snow adds up. Near Mt Baker, backcountry riders have recently triggered avalanches on the crust and it's not out of the question in this zone. Otherwise, the crust is stabilizing the lower snowpack including the weak layer associated with the widespread natural avalanche cycle on the 19th.  This thin layer, which at one time was small facets buried on December 12th, is now about 3 feet below the surface and can be found just above a layer of frozen melt forms or a crust. These old facets (now mostly seen as softer rounded grains) were responsible for the persistent slab avalanche cycle and the layer is now unreactive. In isolated areas, you may still find the Dec 12th layer showing up in snowpack tests, but very large and destructive avalanches on this layer are unlikely.

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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