Avalanche forecast

Stevens Pass

Mar 11 – 12, 2020Northwest Avalanche Center
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Archived · expired 7 years ago

Avalanche danger

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

Updated: 7:15am on March 11 because less snow fell than forecasted.

You can trigger shallow slab avalanches in alpine, wind effected terrain. Use visual clues to identify areas of recent wind drifting, and steer around these pockets on slopes that are steeper than 35 degrees. If the sun comes out, expect loose wet avalanches on steep slopes that face the sun. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    A few inches of new snow may be drifted into deeper and thicker slabs at higher elevations. Use caution in wind-exposed upper elevation terrain with slopes 35 degrees and steeper. Look for wind textured features as you gain elevation to identify problematic areas of wind slab. Use small, inconsequential test slopes to check how these drifts react to your weight. You can also use your pole or quick hand pits to check how the new snow is bonding to older snow surfaces. Defer to well supported, or lower angle slopes if you find signs of instability. 

    It's March 11, and the sun is strong when it shines. With a fresh blanket of new snow, keep loose wet avalanches in mind as the daytime begins to warm up. If the sun does come out, expect these to happen on slopes that face the sun after just a couple hours of sun hit. Even small loose wet slides can be powerful on steep slopes, and you don't want to get caught off guard in the wrong place. 

     

Snowpack Discussion

March 5, 2020 (The regional synopsis is updated every Thursday @ 6 pm)

 

Ridgetop wind transport near Washington Pass. 3/4/20 Photo: Josh Hirshberg

 

The beginning of March brought the first spring-like weather to the region. The days are getting longer and the sun (when it shines) has a noticeable effect on the snow. Alternating sun breaks and snowstorms is the theme of the week and the avalanche danger fluctuated just as fast as the weather. The southern zones and the east slopes have seen periods of light snowfall and significant sunshine while the northern zones and west slopes have had significant snowfall and occasional sun breaks. Above freezing temperatures were common at lower elevations throughout the region. 

Last week in review:  Temperatures were above freezing at most trailhead locations and concerns about the previous week’s buried surface hoar and weak layers were fading. Saturday temperatures plummeted as strong winds and new snow built wind slabs in most areas and drove the avalanche danger to considerable in almost every zone. Sunday’s calm weather and clearing in most areas helped stabilize wind slabs, but our attention turned to the strength of the sun and daytime warming. Lingering wind slabs and loose wet avalanches were forecast in every zone. For the remainder of the week, the avalanche problems in every zone were confined to the recent snow and each brief storm cycle had us thinking about wind slabs at upper elevations and loose wet avalanches from daytime warming and sunshine.

Spring isn’t actually here -- another round of cold temps and snow showers are on the way this weekend, but this past week’s oscillating weather is a good reminder to begin to shift our mindset. The sun is gaining strength, the days are getting longer, and we begin daylight savings this week. Even a brief period of sunshine can dramatically alter fresh, new snow. Check the mountain weather and avalanche forecasts for the most up to date info, enjoy the backcountry and let us know what you see out there!

--Peter Moore

Wet loose avalanche debris near Snow Lake. 3/5/20 Photo: Dallas Glass

Fresh cornice development from strong winds in the Stevens Pass backcountry. 3/4/20 Photo: Tom Whipple

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