Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

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

With only mild cooling and a cloudy night, you can still trigger wet avalanches in steep terrain. Very large avalanches are also possible in specific areas. They may start in upper elevations and run into seemingly safe terrain below. Avoid travel in large alpine terrain and exposure from slopes above and avoid steep terrain features at lower elevations. 

Avalanche problems

  • Loose Wet

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

    Weather stations throughout the East Central zone reached temperatures well above freezing on Wednesday. Temperatures are forecasted to cool slightly, and snow levels may lower to 5000ft. However, some light rain and cloud cover may prevent the snow surface from refreezing overnight and into Thursday. With a wet snow surface, you can still trigger wet loose avalanches in steep terrain. If you see roller balls or small test slopes show wet snow that gains momentum and additional snow as it flows downhill, avoid traveling on steep terrain features. Also, be cautious of traveling above rocks, cliffs, creeks, or other obstacles that can increase the consequences of getting caught. 

    (1/6/2022)

    Example of a Wet Loose natural avalanche.

    Photo: ONP rangers

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3.5

    Continued mild temperatures overnight may prevent a crust from forming on the snowpack's surface, leaving a possibility of triggering very large and destructive avalanches on deeply buried weak layers. You are more likely to find this problem in the Wenatchee Mountains and areas further East of the crest. These current conditions are a low likelihood, high consequence situation, and being caught in one of these avalanches would likely be unsurvivable. The surface of the snow is presumably saturated, and these avalanches may be wet and run through elevations bands. On Wednesday, an NWAC forecaster observed very large avalanches off Wedge Mountain in Leavenworth. Other than continued reports of isolated large to very large avalanches, we have little information on the snowpack since the Jan 5-8th storm. With the uncertainty surrounding this problem and the destructive nature of these avalanches, it will be imperative to avoid being in or under terrain that could produce them. Stay out from under any large, open alpine terrain.

    In the open foothills, these avalanches may be easier to initiate. Stay off of steep slopes if they have not avalanched yet.

    (1/10/2022)

    Deep slab- ENE Facing at around 5,400ft off Pt 5510 above Iron Creek, near Blewett Pass. (Estimated: HS-N-R2-D2.5-O).

    Photo: Matt Primomo

Avalanche Discussion

It has only been four days since the East Central Zone received 3-4ft of new snow. Over the last two days, we have had warm temperatures and rain. As a result, it has been an ever-changing and sustained avalanche cycle. We have gone from very large dry snow avalanches to wind slabs to wet snow avalanches. And large avalanches are still being reported in the Wenatchee mountains surrounding Leavenworth. This is a lot of rapid loading for the snowpack to handle, and it likely needs more time and hopefully some cooler temperatures to truly bring this cycle to its conclusion. We also have a highly variable snowpack from west to East in the zone and little to no information except for what we can see from low elevation roads and towns, leading to significant uncertainty in our forecast. 

We know that before and during this storm, large and very large avalanches ran naturally and were triggered by explosives on a variety of deeply buried weak layers. The more recent layers consisted of large stellars, facets, and surface hoar from 1/2 and 12/29. A decomposing crust from the Solstice was the bed surface for some slides at Mission Ridge. An even deeper crust from Early December showed propagation potential on high elevation, shaded slopes in the Icicle drainage. These layers are likely buried 3 to 8ft deep and could still be capable of producing avalanches.

Many great Observations have come in from the area. Thanks, and keep them coming as we unravel the saga of last week's storm and move into this current storm and avalanche cycle.

 

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