Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

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

Another round of precipitation could help to thicken existing Wind Slabs or be drifted into shallow new ones on Friday. Look for these unstable pockets of wind-drifted snow near ridgelines or rocky features. In some areas, new snow could be overlaying buried weak grains, allowing for the possibility of surprising avalanches to occur.

Avalanche problems

  • Wind Slabs

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

    Recent windy weather throughout the zone has re-distributed snow onto a variety of aspects and elevations, potentially creating Wind Slabs for you to avoid on Friday. You could find that the easterly winds we’ve experienced lately have created some unusual trigger points for these slabs. Reverse loading onto aspects you’re not used to, plus mid-slope cross-loading are commonplace with east wind events and were reported by professionals near the crest on Thursday. Evidence of the recent windy weather shouldn’t be hard to spot - textured surfaces, smooth pillow-like piles of snow, and firm wind-press will likely greet you in exposed areas on Friday. These visual clues can help you identify wind-loaded features to avoid. Slabs will likely be larger and possibly more reactive as you ascend in elevation toward ridgelines. They also like to form on convex features or near rocky outcrops, regardless of elevation, so investigate these areas carefully and choose a different path if you suspect them to be wind-loaded.

    (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

Avalanche professionals near Crystal Mountain and White Pass both reported that freshly fallen snow was being redistributed by the gusty winds on Thursday. In some locations, features were heavily cross-loaded, while other areas were stripped bare down to the Christmas Crust. Near Crystal, some very small pockets of Wind Slab failed naturally and others were triggered by skiers on steep convex slopes. Down at White Pass, a similar story was relayed, but higher snowfall totals resulted in slightly deeper slabs and a few mid-storm instabilities. 

The other interesting observation from White Pass is that additional preserved buried surface hoar was found around 7 inches below the surface. It was identified on a variety of aspects compared to only being found on northerly aspects on Wednesday. No avalanches were reported on this layer and large column tests showed no signs of propagation. However, the layer showed up consistently in small column tests, was easy to spot in the snowpack, and was well preserved when examined by professionals. Should we wave our arms about this? Maybe not yet - we haven’t seen any avalanches on it. But we know it exists in the snowpack (at least at mid-elevations at White Pass) and as we incrementally load this layer a few inches of snow at a time, we could reach a tipping point resulting in avalanches. Slabs failing on buried surface hoar can break in surprising ways such as spanning far distances, breaking above you, or connecting/wrapping terrain features. If you experience whumpfing collapses, see shooting cracks, or see avalanches breaking in this manner, dial your terrain selection way back to avoid slopes over 35 degrees. Additionally, in the neighboring Mt. Hood zone, a vague report of possible buried surface hoar was received on Thursday. If this turns out to be true, it wouldn’t be a stretch to assume that this layer could be spread further south to the Mt. Adams and Mount St. Helens areas of our zone. More work to be done, stay tuned.

On Friday, you could experience conditions similar to how Thursday unfolded. Precipitation is set to continue, but the winds should switch direction and decrease in ferocity. The amount of new snow will be variable across the zone, so keep an eye on the amount of new accumulation wherever you are recreating. If you’re on a volcano or an area that gets more than 6” of new snow, you could find that slabs are deeper and triggering more easily, leading to locally higher hazard. At lower elevations, precipitation may come in liquid form in some areas. If you notice rain falling on dry snow, you could experience some rollerballs or other Wet Loose activity. In this case, if you start to see fan-shaped avalanches, simply head for lower-angled slopes.

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