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Avalanche Forecast

Archived

Dec 26th, 2021–Dec 27th, 2021

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

Regions

Jasper.

Happy Holidays to everyone from Jasper Visitor Safety team! 

Weather Forecast

Monday will be a mix of sun and cloud, no new snow, -22C and Westerly light winds. Tuesday will bring sun and flurries, -30 to -20 C, and light Northerly ridge winds. Wednesday will be similar to Tuesday.

Snowpack Summary

35cm of snow arrived Dec 22-23 with moderate to strong SW winds. Wind slab developed in the alpine and on exposed terrain features at treeline. The winds have shifted Northerly so expect reverse loading. The mid-pack is supportive with an exception of a weak rain crust 30-40 cm down found up to 1950m. Cold temperatures will accelerate faceting.

Avalanche Summary

Friday's avalanche control produced numerous 30cm thick wind slabs up to size 2 on wind loaded open tree line features. One result buried the road 2m deep for a 100m. Surprisingly, explosives did not trigger the deeper instabilities. Numerous loose dry explosive triggered and natural activity also occurred up to size 1.5. No patrols since 24th.

Confidence

Due to the number of field observations

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

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.