Avalanche forecast

East Slopes South

Northwest Avalanche Center
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Avalanche danger

Tue
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

1- 2 feet of snow fell throughout the East South during the past two days, and the snowpack is still adjusting to this new load. While the overall likelihood of triggering an avalanche has decreased, there may still be lingering unstable slabs of snow, especially where the wind has blown the snow into deep drifts. Use small test slopes to assess how well the snow has bonded to the underlying surfaces. Approach large open terrain near ridges and steep rolls within the terrain cautiously, especially on north aspects, where you are most likely to trigger a slide. 

 

Avalanche problems

  • Storm Slabs

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

    The storm has drifted to our south, and while you may see some lingering showers overnight, the main event is over. The East South zone ended up with 1-2 feet of new snow and more where the winds blew the snow into deeper drifts. Whenever a rapid change like this much new snow occurs, it will take some time for the snowpack to settle and adjust. The overall trend in avalanche danger is decreasing, but there could be areas both in wind-loaded terrain and sheltered terrain where you could trigger large avalanches. You can expect these avalanches to be larger at higher elevations and in locations with wind drifted snow. This new snow fell on various surfaces, including crusts, older snow, and potentially weak sugary faceted snow or feathery surface hoar. We have limited observations from the zone, which increases the uncertainty of the distribution of these weaker snow layers. But we suspect they will be more likely on northern aspects sheltered from the sun and wind. Approach new terrain slowly and assess conditions as you ascend in elevation. Before committing to steep slopes, observe the bond between the old snow and new snow layers using quick hand pits or jumping on steep, inconsequential, small test slopes to see how the snow reacts. If you find layers that slide easily or test slopes produce mini avalanches, you should stick to lower angle slopes. 

    (12/10/2022)

    A distant view of the skier-triggered avalanche at White Pass on 12/10. This slide is suspected to have failed on buried surface hoar. 

    Photo: Paul Przybylowicz

Avalanche Discussion

The East-South exceeded precipitation amounts for this storm, with Green Lake and Lost Horse SNOTELS recording over 1.5 inches of precipitation. This likely translated to 1-2 ft of new snow, which is a significant new load for the current snowpack. 

Adjacent zones to the north, south, and west have had avalanches on weak snow buried either just below the recent storm snow or deeply buried near the ground. During avalanche control efforts on Sunday, Crystal Ski Patrol produced a large avalanche that ran down to the ground on weak-faceted snow that formed in mid-November. Mission Ridge ski area also produced avalanches on this same layer during avalanche control on Saturday. Other observations have rolled in from the White Pass area of avalanches on buried surface hoar just below this recent storm snow. While we have limited direct observations from the East South zone, avalanches on this layer are widespread enough to impact the East South Zone. I was out in Ahantum Meadows earlier in December and found a similar structure. While it did not seem reactive in that particular location, we remain suspect of higher elevations and northerly aspects. This uncertainty should make you take a step back and closely evaluate shaded slopes that may harbor this weak snow.  

With a sunny day in the forecast tomorrow, you may see roller balls or wet snow sliding off steep terrain near rocks or cliffs.

If you get out into the East-South Zone, tell us what you see by submitting an observation on our public observation platform! These observations play an integral role in producing a quality avalanche forecast but also help the greater backcountry community.

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