Avalanche forecast

West Slopes Central

Northwest Avalanche Center
View on map

Avalanche danger

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Out of date — this forecast expired 5 years ago.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

Highlights

The potential for human-triggered avalanches in wind drifted snow lingers at upper elevations. Ease into terrain slowly and steer around large unsupported slopes 35 degrees and steeper with evidence of wind loading. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    You may still be able to trigger an avalanche in wind drifted snow on upper elevation slopes 35 degrees and steeper. Of most concern are north-facing convex and unsupported slopes and areas below cornices and rock bands. Several human-triggered wind slabs and a few close calls occurred over the past several days in the adjacent West North Zone. On Saturday a backcountry skier triggered a wind slab avalanche in the Whitehorse Mountain area near Darrington.  It was about 10 inches deep, on a north-facing slope at about 4800ft.  You can read the observation here. Fortunately, there were no full burials or injuries. Avalanches in wind drifted snow could break 6in-3ft deep on a variety of mid-storm interfaces or on a crust that formed up to 6000ft on March 4. Continue to approach upper elevation terrain cautiously, and give cornices a wide berth. These unpredictable features are large and overbuilt and can break further back than you may expect or fall onto slopes below acting as huge triggers. Seek out terrain less than 35 degrees where you find recent avalanches, cracking, collapsing, or evidence of wind drifted snow. 

    (3/8/2021) A snowboarder riggered avalanche on Shuksan Arm that broke 1-3ft deep, 200ft wide, and ran 300 vertical feet. The snowboarder dropped the cliff above the slope and triggered the avalanche upon landing. They were caught and carried but remained on the surface with no injuries. Photo: Pete Durr

Avalanche Discussion

There are dormant layers (mid-January PWL) in our snowpack buried over 10ft deep that produced widespread avalanche cycles and ongoing very large natural avalanches throughout the region for the entire month of February. The adjacent West North Zone was the first to see a major cycle on the layer February 1-2, and isolated but very large natural avalanches as recently as February 25. In the West Central Zone, and in other parts of the region (Stevens, Snoqualmie, West South, East Central) very large and widespread natural cycles on the mid-January layer occurred February 22-25, and as recently as March 1 at Stevens Pass. With quiet weather, no new deep slab avalanches in over a week, and consistent and favorable results in snow profiles and tests, there is enough evidence and confidence to remove the problem from the  West Central forecast for now. Regardless, we will continue to track the Mid-January PWL throughout the region for the remainder of the season. We will not soon forget the very large deep slab avalanches from February, and recognize these types of avalanches are challenging to accurately assess and forecast. It is not out of the question for large triggers like cornice fall to still cause a deep slab avalanche, and a significant weather event may even be enough to reactivate the layer and bring the problem back to life at some point again this season.  

From March 4-7, at least 1ft of new snow accumulated above 4000ft throughout the West Central Zone. Dry sunny weather arrived Monday with increasing clouds Tuesday. The strong March sunshine affected cold snow surfaces since the storm ended with widespread loose wet activity and melt-freeze crusts on solar aspects reported in adjacent zones. Deposits of wind-blown snow are now a few days old, but may still be reactive to human traffic especially high in the alpine. In the West North Zone, several triggered wind slab avalanches were reported in the past 48hrs in upper elevation terrain on Shuksan Arm, Table Mountain, and on the south side of Mt. Baker. Most were small and predictable, but some broke deeper, wider, and grew large. Mostly cloudy skies Wednesday are expected to limit additional wet loose activity, while a full day of sunshine is set for Thursday.

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