Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 3 years ago.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

Highlights

We are in store for another night of strong winds, and you could still trigger avalanches in this wind-drifted snow. Watch for signs of instability, such as cracks shooting away from your equipment, and avoid steep slopes where you find "fat" looking, textured drifts of snow. If you are close to the crest between HWY2 and I90, expect significantly higher snow totals and potentially higher danger. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–2

    Weather stations recorded sustained winds over 30mph for 7-12hrs on Thursday and drifted snow into wind slabs even at lower elevations. Expect moderate and gusty winds to continue drifting snow throughout the day on Friday before tapering later in the afternoon. So any steep open terrain will potentially harbor large wind slabs, but avoiding these wind slabs in alpine terrain will be especially challenging. The most likely places to trigger these avalanches will be steep slopes below ridges, steep convex rolls, and the base of cliffs. Feel for stiff over soft snow layering and look for signs of cracking or collapsing to identify and avoid areas of unstable wind-drifted snow.A convergence zone between Stevens and Snoqualmie Passes wrung out significantly more snow near the crest in this narrow band from north to south. As a result, you may find unstable storm slabs in these areas. Watch for signs of instability, such as shooting cracks, collapsing, and recent avalanches, as red flags to avoid steep terrain. You can use small, inconsequential test slopes and quick hand pits to observe how the new snow reacts. Avoid steep terrain if you find the new snow sliding easily or test slopes producing mini avalanches.Sheltered terrain with low-angle slopes will be the best option to reduce to likelihood of triggering an avalanche. 

    (2/28/2023)

    A small wind-loaded test slope produced this mini wind slab. 

    Photo: Katie Warren

Avalanche Discussion

It may seem like most of the East Central zone missed out on those significant storm totals we discussed in the forecast on Thursday. Strong winds, intermittent snow, and sun breaks summed up the day in the eastern valleys. However, the convergence zone parked directly between Stevens and Snoqualmie and areas near the crest between Upper Salmon La Sac and the Upper Icicle Creek drainage likely picked up over a foot of new snow. There is still a possibility of this convergence drifting north or south overnight, and depending on this pattern, other areas could see additional snow accumulations Thursday night. So monitor new snow totals as you travel and expect that conditions in the area you are traveling in could have locally higher danger if you find more than 6-8 inches of new snow. Low-elevation areas further east in the zone received little new snow, and it is probably unlikely to trigger an avalanche in these areas. 

New snow accumulated over slick crusts on southerly aspects and weak surfaces on northerly aspects, so the reactivity of the storm snow could vary significantly with aspect. You might see Dry Loose avalanches running on these slick crusts.  Enter new terrain slowly and observe the new, old snow interface before committing to steep or consequential terrain. You can find 1-3ft of recent snow sitting over a crust from Valentine's Day, which often presents as a crust/facet sandwich, with weaker snow beneath the upper crust. Observations indicate quite a wide variability in the structure of this layer. There has been a couple of isolated observations of instability on this layer in the Icicle drainage. We have yet to observe avalanche activity on this layer but continue to monitor it as snow adds up. If you get out into the mountains, submit an observation to share what you found.

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