Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

Sun
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Another potent storm will impact Snoqualmie Pass, resulting in dangerous avalanche conditions on Saturday. Unstable snow, recent human-triggered avalanches, and dynamic springtime weather should lead you to dial back your terrain choices and avoid slopes over 35 degrees.

Avalanche problems

  • Wind Slabs

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

    We haven’t finished dealing with the last storm’s instabilities yet and we are moving right into more stormy weather Friday night into Saturday. Fresh snow and moderate to strong winds will aid in Wind Slab development on leeward slopes near ridgelines, on convex rollovers, or near rocky features such as cliffs and gullies at all elevations. You can use visual clues such as actively blowing snow, textured snow surfaces, or freshly built cornices to help you identify wind-loaded slopes to avoid. Although wind-loaded terrain could be the most likely location to trigger an avalanche on Saturday, that doesn’t mean that you can’t trigger an avalanche on slopes over 35 degrees or convex rollovers in wind-sheltered terrain. Use small test slopes and hand pits as you travel to test the reactivity of the recent storm snow and avoid slopes over 35 degrees if you find a poorly bonded interface or suspect wind-loading.

    (4/9/2021) This skier triggered Wind Slab occurred on 4/9 and ran 600 verticle feet, carrying a skier as it descended. A second slab was triggered as debris overran cliffs onto lower slopes. [N aspect 4700']

Avalanche Discussion

On Friday, multiple skier-triggered avalanches occurred at Snoqualmie Pass, including an involvement where a skier was caught and carried (size D2, with a 2' crown). These reports come a day after two separate skier-triggered avalanches occurred in close proximity in the Alpental Valley (on Thursday), and cap a week of near-misses and avalanche involvements throughout multiple zones in the Cascades. At Snoqualmie Pass alone, we have had a week that produced natural glide avalanches almost burying multiple parties and now dry slabs catching multiple parties off guard. We continue to bring up that the snowpack has not made its full transition to a springtime snowpack, and this past week provides proof with both dry and wet avalanche problems driving these involvements. 

The storm on Wednesday night delivered up to 16” of snow above 4500’ at Snoqualmie Pass, which was drifted into deeper piles by strong winds and sits atop a stout crust on most aspects (4/7 interface). In some locations, a layer of graupel has been observed at the base of the storm snow and was confirmed as the failure grain in Friday’s avalanche involvement. The 4/7 interface is still a concern going forward and will only be buried deeper by the incoming storm (possibly as much as 3 feet). On slopes that see direct sunshine, small wet loose avalanches (up to size D1.5) were observed in the Alpental Valley on Friday morning and cornices were noted to have grown large in some locations. Although cool temperatures and mostly cloudy weather should dominate the day, if the sun makes an appearance, expect similar wet avalanche problems to develop again. Avoid slopes that see direct sunshine if you notice the snow surface getting sticky and wet, see fresh rollerballs, or recent avalanches with fan-shaped debris. Continue to be aware of your overhead hazards at all times - limiting your time beneath cornices and glide cracks. 

As you can see, conditions are dynamic right now.  As we navigate our way through springtime weather, the transitions between dry and wet avalanche problems can be rapid and unpredictable, just like the weather. It can make decision-making and forecasting challenging since you can’t bring your winter mindset or spring mindset to the mountains to rely on for any given day. Perhaps the best advice is to learn from these recent incidents and dial back your terrain choices until more stable weather and snowpack patterns prevail.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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