Avalanche Forecast

Archived

Dec 17th, 2023–Dec 18th, 2023

Alpine

Natural avalanches unlikely, human triggered possible.

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.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

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

Although the danger rating has dropped to M/M/L, the thin, generally weak and shallow snowpack is not to be trusted. Supported and low angle terrain are still your best bet for linking a couple turns here and there.

Confidence

Moderate

Avalanche Summary

A road patrol today showed no new avalanches in the Spray area.

Snowpack Summary

Although there are windslabs out there, with no new snow and fetches being stripped dry, they have built as much as they can and are losing sensitivity at this point. Up to treeline, expect to encounter a rain crust down 20-30cm that formed in an early December storm. So far failures on this crust have been few, but as it develops we expect this layer to become a common bed surface for avalanches. A surface hoar layer is also found up to treeline beneath this crust that was producing moderate results in snowpack tests. Deeper in the snowpack a weak basal layer persists that was a thin melt freeze crust in some areas, or just weak basal facets and depth hoar. Thin areas are still common places to trigger these windslabs which are likely to propagate across a feature so keep this in mind as you travel.

Weather Summary

Sunday night will cool to -7 and winds will be steady out of the West at 35km/h.

Monday: A mix of sun and cloud. No snow to speak of and freezing levels to rise to 2000m (Spray road elevation is 1800m)

Winds will continue to from the SW at 25km/h

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Approach lee and cross-loaded slopes with caution.
Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.
Watch for areas of hard wind slab on alpine features.

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.