Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Mon
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

In alpine terrain near ridgelines, older stiff slabs of wind driven snow could rest on weak, sugary snow grains. These avalanches may be isolated to specific steep terrain features at the highest elevations, but we have limited information. As you ascend in elevation, use your probe or ski pole to identify stiff snow over soft snow and note any pillow-like snow features that feel or sound hollow. You may also notice and feel the snowpack loudly collapse beneath you. These are all signs to stick to low angle terrain.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    NWAC forecaster Josh Hirshberg was out at Washington Pass on Saturday. In an isolated area above 7000ft, he observed a large collapse in a wind slab overlaying a thin layer of weak snow. We have limited observations on the extent of this problem, but high elevations near steep, rocky ridges are the most probable location. Continued east winds may add depth to these potential avalanches, and they could become quite large. While it has been over a day since the last significant wind event, these snowpack conditions can be slow to heal. As you ascend in elevation and begin to approach wind affected open terrain with sparse vegetation, you can quickly dig down to identify any weak snow layers with stiffer slabs on top. Make multiple observations as you climb and consider using very small, steep, but inconsequential terrain features as test slopes. If you can get a mini slab to break on these test slopes, you should stick to low angle terrain in areas sheltered from the wind. While we're focused on older wind slabs, there is plenty of low density snow to blow around. Pay attention if the wind picks up, and you observe drifting snow. New shallow wind slabs may form throughout the day.

    (12/3/2022) Very shallow 2-3" chunks of wind slabs could be initiated on kickturns above treeline. Hairpin valley, SW, 7,000ft. Photo: Josh Hirshberg

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    All this new snow feels bottomless, which is because it is so dry and cohesionless. Before engaging with very steep wind-sheltered terrain, take stock of your surroundings. Sun and cold temperatures may make loose avalanches possible in very steep terrain. These small Loose avalanches in extreme terrain may be all it takes to knock you over and send you on a ride over rocks and cliffs. Even these small avalanches could bury you if you are caught in a steep gully or pushed into a creek. 

     

    (2/27/2022) A natural loose dry avalanche, size D1.5 that occured on February 27th, 2022. 6,500ft WSW, Cutthrout creek. Photo: Josh Hirshberg

Avalanche Discussion

We're starting to better understand the early season snowpack in the zone. The recent storm snow is generally well settled above the late November crusts at mid-elevations. Weak snow (facets) exist near these crusts, but no avalanches have been observed on these layers, nor are snowpack tests concerning. Some wind effect has been noted among higher ridgelines and along with fresh cornice growth, but observations are more limited above treeline. Overall avalanche activity has been minimal, with small dry loose avalanches triggered on very steep slopes, and only a one slab avalanche was noted following the Tue/Wed storm.  

Fresh reports from the Washington Pass area and near the Methow Valley describe a weak and shallow snowpack with widespread collapsing and whumpfs felt by travelers. Despite this scary setup, thinner snow depths and a lack of a denser slab overlying the weak snow are likely minimizing the potential for avalanches. We do have critical observations to the south from Thursday, 12/1, where whumpfs and avalanches were reported in the Mission Ridge area, and observers noted collapses outside of Holden and up the Icicle. Persistent slabs are a problem in the East Central forecast. There are likely areas in the East North where the right structure exists, and a persistent slab avalanche is possible. As you step out into winter, watch for direct signs of instability like shooting cracks, whumpfs, and recent avalanches, and adjust your terrain. 

Across the zone, an inch or more of water was recorded at area weather stations Tuesday through Wednesday night. This translated to 12-18" of new snow with a growing snowpack at all elevations. There was a slight warming trend towards the end of the heaviest precipitation Wednesday morning. Snow depths are healthy for early December, in the 3-5' range at mid-upper elevations and 1.5-2' even in the valleys and foothills. The most recent rain crust in the upper snowpack formed after rain fell up to about 7,600ft at Blue Lake Col on November 25th. 

Avoid an early season injury in areas with lower snow cover; be mindful of shallowly buried trees, rocks, and open creeks. And brrrr...it doesn't look like it's warming up any time soon, so make sure to bring extra layers and supplies to stay warm. 

If you're out, let us know what you see by submitting an observation.

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