Avalanche forecast

West Slopes Central

Northwest Avalanche Center
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Avalanche danger

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

You could find wet loose and also slab avalanches of recently drifted snow Friday. Look for signs of instability in terrain overhead with warming conditions. Identify and steer around wind loaded terrain features like steep slopes just below ridgeline and convex rollovers.

Avalanche problems

  • Loose Wet

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

    Loose wet avalanches will be most likely earlier in the day before clouds roll in and start blocking the sun. Some areas may have already seen significant sun, warming, and wet avalanche activity earlier in the week while others did not. Either way, when the sun is out in mid-April it's best to keep track of what’s going on above you no matter what the aspect or elevation.

    If you experience warm temperatures and strong sun, start looking for the usual signs of instability like wet, unsupportable snow surfaces, rollerballs, or small avalanches. Avoid travel on and directly under steep slopes where you see the above. If a firm crust tops the snow surface then wet loose avalanches are unlikely.

    Wet loose avalanches near the  Mountain Loop Highway in 2021

    Photo: George Coiner

    Photo: George Coiner

  • Wind Slabs

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

    While wet avalanches are what you are most likely to see Friday, natural and human triggered wind slab avalanches were widely observed a few days ago. They could still be a thing in the right kind of terrain feature like a steep pocket just below ridgeline or a convex roll. Small wind slabs could also have formed in the last 24 hours with moderate winds and a few inches of new snow.

    Wind slabs might be harder to identify where covered by softer snow. Look for fat or pillowy-looking drifts and keep an eye our for scoured snow surfaces, cornice-like features, and changes in snow texture to figure out where wind slabs might lie in wait. You might find that wind slabs are hanging out where the snow is just a bit deeper and a bit thicker than in the surrounding terrain.

    Test slopes and hand pits can help you monitor differences in snow stiffness and layering as you change aspects and gain elevation. Evaluate the bond of wind slabs before easing into steeper terrain - or just find a lower-angled line around areas like convex rolls where you are more likely to trigger one.

    (4/12/2023)

    A skier triggered slab avalanche Wednesday on Mt. Pugh. Signs of wind loading are the small cornice-like features along the ridge and snow stacked up on the uphill side of the trees. 

    Photo: NWAC Public Obs

Avalanche Discussion

There were few observations Thursday. The primary information was that there were a few inches of new snow around the Baker Backcountry in West North and observers in Snoqualmie Pass reported the new snow was starting to bond to the crust below. Those who still pick snowmobiling, snowboarding, snowshoeing, and skiing over non-snow activities likely took the day off between sunny weather on Wednesday and more in the forecast for Friday. Overall it was a cloudier and cooler day with moderate winds overnight. 

By the end of Wednesday, it was apparent that avalanche danger for that day - and maybe the day prior -  was greater than forecast. Numerous wind slab and wet loose avalanches were reported from across West Central and West North, naturally and also human triggered. Most were on the smaller side of things at D1.5 or less but a few were probably larger. All released at or above the crust interface buried by new snow Tuesday. Slightly older avalanches (D2.5-3) were also reported. Most are suspected of releasing during the big storm and rain event last weekend.

Solar aspects should have some sort of crust while the steepest shaded aspects might still hold good snow. Below the most recent snow, the upper snowpack structure is comprised of dense rounded grains separated by melt-freeze crusts formed by rain and sun. While it is unlikely a person could trigger a slab avalanche below the old-new snow interface, larger avalanches out there show us that deeper layers can always wake up with heavy loads of new snow, rain, or big triggers like cornice fall or a smaller avalanche.

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