Avalanche Forecast

Archived

Dec 7th, 2023–Dec 9th, 2023

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

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.

Regions

Kananaskis, Bow Valley, Highwood Pass, North 40, Spray - KLakes.

Cycle still ongoing, give the snowpack time to settle to the new snowload.

Confidence

Low

Avalanche Summary

A sz 2 from a north aspect near an outlier of Chester peak scrubbed down to ground in 35deg terrain. Also a few storm slabs up to sz 2 were observed in the Buller corner avalanche control zone that running to the top of the normal runouts.

Miners gully near Canmore was also see to fail in the narrow upper area.

Not all areas were easy to see due to obscured conditions but a common theme was high north terrain.

Snowpack Summary

20cm of recent storm snow in lower elevations with 30-40cm of snow at treeline and above. This storm snow fell with light winds and warm temps and as a result has been quickly settling into widespread storm slabs in the upper snowpack. Below 2100m the basal layers are wet facets as a result of the rain preceding the storm. Recent rain squished down the surface hoar in many areas but as you move up into treeline areas, be curious and look for this interface as its more spotty in nature. Generally 50cm at treeline and 70-90cm in alpine areas is the norm. In some areas the rapid loading has overloaded the weaker basal facets causing avalanches that are failing at or near the ground. This was seen today with slides on N aspects from alpine terrain. With this being our first major loading of the snowpack, take it easy and give it time to adjust. Its still very thin out there and thinner snowpack areas are likely places to trigger an avalanche.

Weather Summary

Well the majority of the snow is over as the storm passes overhead. Winds will be light out of the NW with freezing levels at the valley floor. Light flurries overnight will end and a mix of sun and cloud should be expected on Friday.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Continue to make conservative terrain choices while the storm snow settles and stabilizes.
Approach lee and cross-loaded slopes with caution.
Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
Any steep opening in the trees should be treated as suspect right now.

Problems

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.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.