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Avalanche Forecast

Archived

Dec 15th, 2022–Dec 16th, 2022

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

Regions

South Rockies, Akamina, Bull, Crowsnest North, Crowsnest South, Elkford East, Elkford West.

Watch for pockets of fresh wind slab at ridgetop. A buried weak layer looms in the west and central parts of the region. Check out our latest blog for advice on managing persistent avalanche problems.

Confidence

Moderate

Avalanche Summary

In the good visibility on Thursday, our field team observed three large natural size 1.5-2 persistent slab avalanches in big alpine terrain features near Elkford. We suspect they are of similar age as another avalanche reported in the same area on Tuesday. All are suspected to have run on the buried weak layer from November. This weak layer continues to show easy propagation in snowpack tests. In neighboring regions where it is buried deeper, this layer has produced several alarming rider-triggered avalanches.

Otherwise, avalanche activity in the region has been limited to explosive triggered wind slabs size 1-2 in the east of the region.

Snowpack Summary

A thin surface crust may be found on steep south aspects. As ridgetop winds start to pick up from the northwest on Friday, 5-10 cm of recent snow is likely being reverse-loaded into atypical terrain features. Older wind slabs on more typical aspects, or soft snow in sheltered areas may sit over a layer of buried surface hoar in the east of the region.

A weak layer consisting of facets and surface hoar formed in November is now buried 45-65 cm deep in the west and central parts of the region. In the east, it may exist as a crust on solar aspects. This layer has produced large avalanches in recent days and continues to show reactivity in snowpack tests.

The lower snowpack consists of sugary and faceted snow, with a thick rain crust near the ground.

Total snowpack depths at treeline elevations are 75 to 155 cm.

Weather Summary

Thursday night

Clear. Light northerly wind. Alpine low -15 C.

Friday

Mostly sunny. Ridgetop wind increasing to moderate-strong northwest. Alpine high -10 C.

Saturday

5-10 cm new snow. Light to moderate southwest ridgetop wind. Alpine high -15 C.

Sunday

Flurries. Light wind. Alpine high -22 C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.