Avalanche Forecast

Archived

Dec 8th, 2023–Dec 10th, 2023

Alpine

Natural avalanches possible, human triggered probable.

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 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.

Regions

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

Expect windslabs to quickly develop as westerly winds move into the region on Saturday. Keep an eye on weather patterns as you travel. We may see the danger return to HIGH in the Alpine if the winds are stronger than forecast.

Confidence

Moderate

Avalanche Summary

A few new sz 2 avalanches were observed from steeper areas and a few isolated slab avalanches within the storm snow were also observed. Tent bowl had a size two near the skiers left lines and EEoR had a sz 2 from the upper bowl that stopped in the upper track.

Snowpack Summary

Forecasters were out at Burstall pass on Friday for the first visit to the profile site this season. In the profile we found 35cm of recent storm snow overlying a 5cm thick rain crust that formed at the start of the storm earlier this week. It is likely that this crust does not exist in the Alpine but more observations are needed to determine the upper limit of this layer. Deeper in the snowpack down 55cm was the Dec 1st Surface hoar layer that had crystals up to 3mm. The bottom 40cm of the snowpack consisted of moist facets to ground.

The recent snow has settled into a soft storm slab that was cracking on top of the rain crust in steeper terrain. Numerous whumpfs were also heard as the moist basal facets collapsed closer to ground. Two key layers to remain aware of will be the Dec 5th crust layer and the Dec 1st SH layer that is likely only found on sheltered polar aspects. When the wind does arrive expect windslabs to build quickly with all the available snow.

Weather Summary

Winds will increase on Saturday afternoon out of the west with temperatures overnight expected to become a chilly -15C. No new snow is forecast over the next 24hrs but there is a chance of some precip on Sunday.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Approach lee and cross-loaded slopes with caution.
Continue to make conservative terrain choices while the storm snow settles and stabilizes.
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

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.

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.