Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
View on map

Avalanche danger

Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
Open full map
Out of date — this forecast expired 5 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Strong winds and additional snowfall should create dangerous avalanche conditions by Thursday morning at the Pass. Steer around steep slopes below cornices and where you find wind drifted snow. If the sun comes out in the afternoon, expect conditions to change rapidly and you may see natural loose avalanches.

Avalanche problems

  • Wind Slabs

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

    Strong winds associated with this storm will likely form firm slabs on a variety of aspects and exposed slopes at all elevations. Watch for clues that the wind loaded snow onto nearby slopes. When you see fresh cornices, textured surfaces, or drifts behind objects, anticipate wind slabs. Instead, seek out less wind-affected or lower angled slopes to travel. Due to the strong winds, you may find wind-affected snow well below ridgeline, along the sides of mid-slope gullies, and on any exposed feature. These slabs will form over a firm crust that may allow them to trigger easily and propagate widely. 

    Even in sheltered areas, this storm gives us some concern. The general cooling trend and light snowfall rates should limit storm slab development. However, with the new snow accumulating over a crust, you could see small avalanches fail at the base of the storm snow. Use small slopes to test the bonding of the new snow to the old surface. If you notice slabs failing and propagating over the features, dial back your terrain use and stay off of all slopes greater than 35 degrees. More likely, you will trigger loose dry avalanches that may run quickly over the firm old surface.

    (3/7/2021) Example: Textured snow surfaces like this can help you anticipate which slopes or features could harbor wind slabs. Photo: Ian Nicholson

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    The sky forecast for Thursday afternoon is a bit tricky. With longer days and more dynamic springtime weather, you could see significant sun breaks in the afternoon hours. If this occurs, conditions may change rapidly. The snow on any steep slope receiving direct sunshine could become wet and slide downhill. Watch for snow shedding from trees and new rollerballs to warn you of potentially ensuing loose wet avalanches. If you notice these clues, steer around similar slopes. While these slides should remain small, they could harm you if they carry you over a cliff or into a gully. At upper elevations, cooler temperatures and a very wind-affected snow surface should help limit the potential for loose wet avalanches.

    (2/28/2021) Example: Snow shedding from trees and new rollerballs can indicate loose wet avalanches are possible.

Avalanche Discussion

Snoqualmie Pass could receive 8-12” of snow at mid-elevations my Thursday morning. A Puget Sound Convergence Zone could bring locally more intense snowfall to some locations within the area overnight and into the morning hours. As a result, you will likely encounter the most dangerous conditions in the morning. However, instead of the hazard decreasing throughout the day, the character of the avalanche problem may change. Make sure to select routes that allow you to adapt to the fluctuating conditions. You could need to manage much different avalanches concerns in the afternoon as you return to the trailhead. 

This storm snow will accumulate over a new interface (4/7). On most aspects, this will be a firm melt-freeze crust. As a result, avalanches running on this potentially smooth bed surface could travel quickly. On northerly aspects above 5000’, this interface could hold dry and potentially weak snow. Professionals found small facets and in a few instances surface hoar on these slopes this week. Spatially variable conditions like this could allow the snowpack to respond differently from one slope to the next.

Just because the weather feels more winter-like doesn’t mean our concern for glide avalanches is gone. These slides can still occur after temperatures fall below freezing. Limit the time you spend below crevasse-like glide cracks. In some instances, these features may hide due to the new snow. You may need a keen eye to identify and avoid this potential hazard. 

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.

Regions covered