Bollettino valanghe

Stevens Pass

Northwest Avalanche Center
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Pericolo valanghe

Tue
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

Continued snowfall and moderate winds will maintain the possibility you can trigger large avalanches on deeply buried weak layers. You could also be able to trigger small avalanches where the wind forms fresh drifts of snow. Look for increasing avalanche danger Monday afternoon as another storm approaches the region. Shift to simpler, lower-angled terrain with less exposure to avalanches if snowfall exceeds forecast amounts.

Problemi valanghivi

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–2.5

    Avalanches that run on deeply buried weak layers could be 3-4ft deep and can propagate widely across the slope. You won't get signs of instability before triggering one, as the layer is too deep. Your best bet is to remain aware of the terrain around you, staying out of complex alpine terrain and off of steep, unsupported, or wind-loaded slopes.  

    The weak snowpack structure has been slow to gain strength. You can find a thin layer of softer facets over a hard crust, about 3-4 feet below the surface. This layering (and the likelihood of triggering avalanches) is most pronounced at upper elevations (above 5,800ft) and further east in the zone. On Tuesday, a skier was buried in a large avalanche that likely ran on the early February facet/crust layer on Jim Hill. See the photo here and more details below.

    (3/5/2024)

    A large triggered slab avalanche likely ran just above the early February crust. A skier was fully buried and quickly dug out by his partners, resulting in minor injuries.  Jim Hill, W, 6,500ft. 

    Photo: Nate Hough-Snee

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    About 6" of new snow overnight and through Monday combined with moderate ridgetop winds should build small but fresh wind slabs. You are most likely to see these just below ridgeline on leeward slopes, but you can also find them on cross-loaded terrain features or even lower on the slope if wind speeds end up higher than forecast. Watch for blowing snow and freshly formed, shallow drifts.  Track variations in snow depth and stiffness as you gain elevation and change aspects. While you can easily steer around these small, fresh drifts, you'll need to avoid triggering the much more dangerous deep persistent slab avalanches. You can trigger these two types of avalanches in similar terrain.

    (12/30/2023)

    Snow plastered on a tree trunk and small drifts help show the local wind direction. 

    Photo: Dallas Glass

Avalanche Discussion

NWAC will be closed Tuesday, March 12th as we gather and grieve following the death of one our forecasters, Matt Primomo. We will not issue regular avalanche or mountain weather forecasts on Tuesday. We will return to normal operations on Wednesday, March 13th. We appreciate the community's understanding and support during this time.

Discussion:

Continued snowfall is forming the next set of layers in the snowpack as Stevens Pass picked up 3-4" inches of new snow by Sunday afternoon with mostly light winds. This snow is likely burying a range of crusts, facets, and possibly surface hoar. Observers reported crusts and wet loose avalanches on steep, sun-exposed slopes in the last week. Since mid-week, avalanches and signs of instability on persistent weak layers have slowed.

A party of three skiers triggered a deep persistent slab avalanche on March 5th on the summit pyramid of Jim Hill, a NW aspect at 6,500ft. The avalanche was approximately 100ft wide and 3ft deep and carried one skier approximately 200ft down the slope. The skier was fully buried but recovered within a couple of minutes with a minor injury. The strengthening March sunshine formed crusts on steep, southerly slopes in the past few days.

On the 3rd, forecasters investigated an older D2.5 (large) avalanche on Jim Hill at 6,200ft, NE. It failed on the weak, faceted snow above the Early February Crust. On the 1st,  forecasters near Skyline Lake found a crust/weak layer just below the February 24th interface that showed a high potential for propagation.  

Your avalanche, snowpack, or weather observations are extremely valuable to the avalanche community. Help create a more accurate avalanche forecast by submitting your observations here. 

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