Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

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

The winds will continue to rip through the West South Wednesday night into Thursday morning, allowing for the possibility of Wind Slabs to develop. Some of these slabs could be overlaying buried weak snow, making them more sensitive than you might expect. If you see smooth pillow-like piles of snow on convex features or near rocky terrain, be sure to steer around them.

Avalanche problems

  • Wind Slabs

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

    Wind Slabs will continue to be the most likely avalanche problem you’ll encounter on Thursday. Easterly wind events can often drift snow onto different aspects than you may be used to and usually result in more mid-slope cross-loading. Regardless of aspect, look for these slabs to develop on specific terrain features such as convex rollovers, the leeward side of ridgelines, or rocky areas such as the base of cliffs and confined gullies. If you can find a small test slope that has a smooth pillow-like pile of snow on it, use the opportunity to see how the snow reacts to your weight to help determine the slab’s reactivity. Actively blowing snow, textured surfaces, and fresh drifts can help you identify wind-loaded features you should avoid. 

    (1/4/2023)

    A very shallow wind pocket  failed on a test slope on 1/4 at White Pass. Notice the textured surface and how it looks "fat" compared to the surrounding terrain. [NE 6400']

    Photo: Dallas Glass

Avalanche Discussion

Wednesday was a windy day around the West South zone, with actively blowing snow creating poor visibility and shallow Wind Slabs. Even a few flurries were observed near the crest at White Pass. That was just an appetizer of the winds to come, however. As of Wednesday evening, the main course is just being served as NWAC weather stations start to record stronger wind speeds throughout the zone. These gustier winds should continue through the evening and into Thursday morning before gradually decreasing during the day. The difference this time around is that the winds should be accompanied by some fresh snowfall, allowing for the possibility of thicker slab development. With the volcanoes set to outpace the crest in terms of snow accumulation, you could experience locally higher avalanche hazard if you travel to those locations on Thursday. Likewise, if areas closer to the crest overproduce on their water numbers, realize that thicker and more dangerous slabs may develop. 

On Wednesday, avalanche professionals near White Pass reported that weak surface hoar was buried intact at mid-elevations on sheltered northerly aspects. The distribution and reactivity of this buried weak snow throughout the zone is not well documented at this point. Keep this piece of information on your radar until we can gather more details. You should be leery of wind-sheltered areas where there is more than a few inches of snow to form a slab. Avalanches breaking on buried surface hoar can act in surprising ways such as connecting terrain features or breaking above you.

The other weather factor to consider on Thursday is that a bump up in freezing levels late morning could result in a bit of upside-down snow in more sheltered locations or some Wet Loose activity at lower elevations. On more southerly slopes, there could be a sun crust from New Year's Day that could act as a good sliding surface. We suspect the majority of avalanches to be confined to the newly fallen/drifted snow. The depth of the Christmas Crust may vary depending on aspect, elevation, and exposure to wind, but we do not have any concerns below this prominent snowpack marker at this time.

Regions covered