Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Tue
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Wet snow falling on already moist snow surfaces maintains the risk of triggering small wet loose avalanches.  Once you move into drier snow, observe signs of wind transport on the shaded or lee sides of ridgelines. Pay attention to changes with elevation and aspect, steering away from open slopes 35 degrees or steeper if you suspect a problem.

Avalanche problems

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    Warm spring-like days have kept lower and perhaps mid-elevation snow moist or wet. Although it might start off cool, a warmer system will arrive in the afternoon with wet snow and rain at lower elevations. This will add fuel for small wet avalanches running efficiently above the stout crust.

    Most wet loose avalanches will be small, so you mainly need to consider your exposure from snow shedding off of cliff bands from above or getting pushed by a wet loose avalanche into a terrain trap like cliffs, rocks, or trees.  If you find yourself sinking into wet snow more than ankle deep or see rollerballs or natural wet loose avalanches on similar slopes, it's time to change location.  You can also choose cooler, shadier slopes or lower-angle terrain.    

    Check out this video by Dallas Glass, highlighting the type of avalanche problem we're dealing with this week.

     

    (4/2/2024)

    D1 wet loose debris in spire gully.

    Photo: Willie Webster

  • Wet Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Upper elevations have consistently seen below-freezing temperatures and should have cold snow on shaded aspects. You can trigger a small slab near ridgelines and where winds have a chance to redistribute cold snow from shaded aspects onto lee slopes. An inch or so of snowfall, primarily arriving during the afternoon, will redistribute in wind-exposed areas, adding to the slabs. In general, your risk increases at higher elevations and on shaded aspects. Look for clues like textured surfaces, sharp wind lips, and fresh drifts to point toward a potentially loaded slope. Although these wind slabs may be growing, these wind slabs should be relatively small and easier toidentify and steer around. Give a little extra margin for error when above terrain traps such as cliffs or gullies.

    (4/7/2024)

    Example: Shallow wind slab.

    Photo: Logan Heine

Avalanche Discussion

Up to 6" of new snow has accumulated above a crust since 4/3. Cloudy and cool conditions Thursday through Saturday have likely helped keep snow surfaces dry on many mid and upper-elevation slopes. That may have started to change at middle elevations with temperatures rising briefly to 35F at Washington Pass elevation.  The recent storm snow is still available for wet loose avalanches if air temperatures approach the freezing mark as a warmer system approaches.

Reports of natural and human-triggered wet loose avalanche activity came in on Saturday and Sunday from a variety of other zones across the Cascades. We're assuming, based on temperatures, that conditions are fairly similar in the East North Cascades. Observers in the East Central zone reported isolated cracking of shallow wind slabs near exposed ridgelines, supporting the potential problem in the East North zone.

On the 4th, an observer on Big Craggy found light blowing snow and shallow new snow accumulation. In the middle of the week, WSDOT forecasters and road crews continued their work to clear Highway 20, Washington Pass. They saw natural loose wet avalanches to size D2 (large) on steep rock slabs. They also triggered some smaller wet avalanches with large explosives. Notably, they couldn't trigger cornices that still loom over sunny slopes.

The snowpack is relatively straightforward. Warming temperatures late last weekend through early in the week drove wet loose avalanche activity. The 3/22 crust is the prominent layer about 1 foot below the surface on high elevation and shaded slopes. On March 31st, observers on Silverstar Mtn assessed the 3/22 crust and but didn't find any signs of instability or concern down to this layer.   If you dig about 3 feet below the surface, you can find remnants of old crust/weak layers, though they are no longer a concern for avalanches. 

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