Avalanche forecast

East Slopes South

Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
2 · Moderate
Treeline
1 · Low
Below
1 · Low
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

A storm will begin during the day on Wednesday, so be ready to take a step back with your terrain selection. Snowfall and winds will pick up and lead to increasing danger as the day progresses. Identify steep slopes of concern to steer clear of if you observe signs of instability like shooting cracks, or if snowfall becomes heavy.

Avalanche problems

  • Wind Slabs

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

    New snow and winds will pick up by afternoon, so avalanche danger will ratchet upwards. Look for signs of active wind drifting and surface textures from wind to clue you into these. The new snow alone could create sensitive, though shallow storm slabs by later in the afternoon. You can use small test slopes to check if the snow could fracture when you provoke it. If its snowing hard, then small loose 'sluffs' could run on steep slopes, especially below cliffy areas. 

    Wednesday should be a nice day to get out, but expect increasing danger. Be ready to take a step back in your terrain selection as snowfall and wind pick up by afternoon. 

    Example human-triggered wind slab.

    Photo: Simon Trautman

Avalanche Discussion

A clash of cold air and moisture laden air should create an excellent winter storm for the zone starting on Wednesday. The storm is only going to begin during the day on Wednesday, but by the end of the day Thursday we could see between 1-2ft of new snow in the mountains. Expect the danger to increase overnight Wednesday, and conditions to become dangerous by Thursday.

Observers have also found widespread surface hoar at Ahtanum, and isolated buried faceted layers at nearby Mission Ridge. These are persistent weak layers that could cause any slab of wind drifted or new snow to fracture wider than you might expect. Previously, a small storm on Sunday night and Monday brought more wind than snow through the area. Other old snow surfaces may consist of thin crusts, settled powder, and firm wind textured snow. 

Earlier in the month, a prolonged period of warm temperatures and rain form what we are calling the Early February Crust. How deep is the EFC? That depends on where you are in the zone. Closer to the crest, it may be 6-8 inches below the surface. Further east, it may be the surface. Expect very thin (or even non-existent) snowpacks at lower elevations and on some steep southerly slopes. Unfortunately, we’re still talking about travel hazards. Slick crusts, exposed obstacles, open creeks, and bare ground continue to make travel more adventurous. Its a good time to use established roads and groomed trails for better access to the high country. 

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