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Avalanche Forecast

Archived

Jan 3rd, 2023–Jan 4th, 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

Lizard-Flathead, South Rockies, Flathead, Lizard, Bull, Elkford East, Elkford West.

Rider-triggered avalanches are still possible where the persistent weak layer is closer to the snow surface in shallow snowpack areas.

Confidence

Moderate

Avalanche Summary

A large (size 2) natural wind slab was reported that started in a steep, alpine terrain feature. Explosive control triggered a small, storm slab in a steep alpine feature.

A rider triggered a small avalanche in an opening, as shown in this MIN. The avalanche likely released on one of the weak layers described in the Snowpack Summary and shows that this layer could still be triggered in specific terrain. Caution should be taken in challenging or complex terrain given the uncertainty and consequence of large avalanches.

Snowpack Summary

20 to 50 cm of snow is being redistributed by light winds in open areas developing wind slabs in lee terrain features in the alpine and treeline. A hard melt-freeze crust can be found up to treeline elevations formed by rain on December 26. A surface crust formed during yesterday's sunny skies may be found up to around 1600 m on all aspects and up to ridgetop on sun-exposed slopes.

Two deeper layers of surface hoar and facets could still be triggered in specific terrain. These include a 40 to 80 cm deep layer buried mid-December and an 80 to 150 cm deep layer buried mid-November. These layers are generally deeper around Fernie and shallower towards Sparwood and Elkford. The layers may be easier to trigger where they are buried within the top 100 cm of the snowpack.

Weather Summary

Tuesday Night

Increasing cloud coverage with a trace of snow, 20 km/h southwest wind, treeline temperature -9 °C.

Wednesday

Mix of sun and cloud, trace of new snow, 20 to 30 km/h southwest wind, treeline temperature - 12 °C.

Thursday

Mostly cloudy, trace of new snow, 10 to 15 km/h south wind, treeline temperature -5 °C.

Friday

Mostly cloudy, 3 - 5 cm new snow, 20 to 30 km/h southwest wind, treeline temperature -5 ºC.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Be especially cautious as you transition into wind affected terrain.
  • Keep in mind that human triggering potential persists as natural avalanching tapers off.

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.