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Avalanche Forecast

Archived

Jan 3rd, 2024–Jan 4th, 2024

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Purcells, East Purcell, West Purcell.

Triggering large avalanches is possible in steep rocky alpine terrain.

Confidence

Moderate

Avalanche Summary

No new avalanches have been reported since a few small wet loose avalanches occurred on Saturday.

Snowpack Summary

The upper snowpack consists of crusts, settled powder, unconsolidated facets, and old wind slabs. Beneath lies a thin and complex snowpack with two notable layers:

  • A layer of surface hoar buried 30 to 60 cm deep has been concerning in areas where it is not covered by a thick crust.

  • Weak basal facets near the bottom of the snowpack, especially in alpine terrain.

While these layers have been a concern for several weeks, they are becoming less likely to trigger under the current conditions.

Snowpack depths at treeline average 50 to 120 cm with significant variability across the region.

Weather Summary

Wednesday Night

Cloudy with trace amounts of snowfall, alpine wind southwest 20 km/h, treeline temperature -8 °C.

Thursday

Cloudy with 1 to 2 cm of snow in the afternoon, alpine wind southwest 30 km/h, treeline temperature -6 °C.

Friday

Cloudy with 1 to 5 cm overnight then partly cloudy in the afternoon, alpine wind west 40 km/h, treeline temperature -8 °C.

Saturday

Cloudy with 2 to 5 cm of snow in the eastern Purcells and 5 to 15 cm in the western Purcells, alpine wind southwest 30 to 50 km/h, treeline temperature -8 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Use caution on large alpine slopes, especially around thin areas that may propagate to deeper instabilities.
  • Be especially cautious near rock outcroppings, on steep convexities and anywhere the snowpack feels thinner than average.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

Problems

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.