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Avalanche Forecast

Archived

Feb 11th, 2021–Feb 12th, 2021

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

Regions

Cariboos.

Cold weather and lingering uncertainty about triggering large avalanches warrants careful travel in avalanche terrain. Read about managing these conditions in this forecaster blog.

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

Brrrrrr! Cold and dry conditions persist under arctic air...

THURSDAY NIGHT: Clear skies, moderate to strong northeast wind, treeline temperatures drop to -30 C.

FRIDAY: Sunny, light east wind, treeline temperatures around -20 C.

SATURDAY: Sunny with a few clouds, moderate east wind, treeline temperatures around -15 C.

SUNDAY: Mix of sun and cloud, moderate south wind, treeline temperatures around -12 C.

Avalanche Summary

No significant avalanche activity has been reported since last weekend, but there have also been few observers due to the cold weather.

Over the weekend there was a very large (size 3) natural wind slab avalanche on a northeast aspect near Valemount, as well as a few size 2 avalanches in the Barkerville area. These included a mix of wind slab and persistent slab avalanches on a 40 cm deep surface hoar layer, mostly on treeline features (see some photos in the MIN reports here, here, and here). One was thought to have been initiated by a machine-triggered cornice fall. In the first week of February there was a flurry of persistent slab avalanche activity on the same surface hoar layer in the riding areas around Valemount and Blue River. Although the likelihood of triggering persistent slab avalanches is decreasing, this weak layer warrants assessment in open, sheltered slopes at treeline where this layer is likely pronounced and preserved.

Snowpack Summary

The upper snowpack is becoming soft and faceted with the cold temperatures, while wind may be forming slabs in lee features. 40-70 cm of snow from February is settling over a reactive weak layer of surface hoar. Reactivity on this layer has primarily been observed at treeline and in "treeline-like" features that are below treeline, although there could potentially be weak snow above crusts on south-facing alpine slopes. Additional weak layers may present in the lower snowpack, but are not a concern in most areas until we see significant snow loading or rapid warming. 

Terrain and Travel

  • Be careful as you transition into wind affected terrain.
  • Carefully evaluate bigger terrain features on an individual basis before committing to them.
  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.

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.

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.