Avalanche forecast

East Slopes South

Northwest Avalanche Center
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Avalanche danger

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

Lingering snow showers and sustained moderate winds have created unstable snowdrifts in open terrain and near ridgelines. You can trigger large avalanches in these deep drifts of wind deposited snow. Avoid steep terrain where you find stiff, hollow-sounding snow or if you see shooting cracks in front of you while traveling.

Avalanche problems

  • Wind Slabs

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

    Plenty of low-density snow is available for transport, and forecasted winds will build new slabs and increase the size of existing wind slabs. Slabs may be larger and more touchy at upper elevations. On steep solar aspects, these slabs could also be resting on top of weak snow on a crust and break surprisingly wide. At lower elevations, wind slabs may linger on open slopes where the wind deposits snow on the lee sides of gullies as it blows across the slope. 

    Use quick hand pits or your probe to look for strong over weak layering. Small test slopes that produce shooting cracks or collapsing are red flag signs that you should avoid steep terrain. Wednesday will be a good day to travel conservatively and steer around wind-affected areas with large pillow-like drifts or hollow-sounding snow. 

    (1/4/2022)

    Recent avalanches in open wind-affected terrain such as these on Blewett Pass are a red flag sign of instability. 

    Photo: Matt Primomo

  • Storm Slabs

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

    While some areas of the Cascades experienced a brief period of dry weather, much of the East South zone continued to receive light snowfall throughout Tuesday. While observations indicate that new storm instabilities are settling out, the continued snowfall will keep the possibility of triggering small storm slabs in the forecast. We expect any avalanches to be within the storm snow from Jan 2nd- 4th, but there is a slight possibility that smaller avalanches could step down to deeper instabilities in the snowpack. Therefore, it will be worth digging into the snow and identifying crusts and interfaces where the overlying snow slides off easily. 

    These slabs most likely linger in steep sheltered terrain, and unsupported slopes or convex rolls are probable locations to trigger these avalanches. Approach new terrain slowly and use small test slopes to observe how the recent storm snow bonds to the old snow interface. 

    (1/4/2022)

    On all aspects, sensitive slabs were breaking 10-15" deep in the recent storm snow near White Pass. [N-E 6300']

    Photo: Dallas Glass

Avalanche Discussion

Wednesday will be the proverbial calm before the storm, with the main event bringing warming temperatures and heavy snow/rain into the region Wednesday night and Thursday. This storm will initiate a rapid increase in avalanche danger. While we don’t expect heavy precipitation to impact the region until late on Wednesday, if you venture out in the evening hours, keep in mind that conditions will begin to change very quickly. 

While observations in East South are limited, this new snow likely fell on a weak snow surface. Underlaying that weak snow is a variety of surfaces, from sun crusts and wind crusts to soft snow. As a result, adjacent slopes and slight variations in aspect may react very differently. We are particularly concerned about steep solar aspects with a few inches of preserved stellar snowflakes, surface hoar, and faceted crystals. On these slopes, avalanches may break farther and become larger than you might anticipate. 

While most observations have indicated a good bond between the upper snowpack and the Solstice crust, now buried 2-3 feet below the surface, some surprising avalanches in other zones have occurred on this layer. Including an explosive triggered slab that stepped down to this layer during avalanche mitigation work at Mission Ridge on Monday. This uncertainty, along with the potentially high consequences of these very large avalanches, warrants extra caution as smaller avalanches may step down to deeper interfaces. 

Regions covered