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Avalanche Forecast

Archived

Feb 27th, 2021–Feb 28th, 2021

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

South Coast Inland.

Watch for fresh, reactive wind slabs which may exist in atypical terrain features. Westerly wind may have southerly or northerly components, depending on elevation.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

Saturday night: Flurries bringing a trace of snow, strong wind above 2000 m, extreme northwest at ridgetop.

Sunday: Flurries bringing a trace of snow. Moderate increasing to strong southwesterly winds above 2000 m. Freezing level around 1300 m.

Monday: 5-10 cm new snow. Strong southwesterly winds. Freezing level 1500 m.

Tuesday: Around 5 cm new snow. Moderate southwesterly winds. Freezing level 1000 m.

Avalanche Summary

Pinwheeling and small loose wet sluffing was observed on steep sun exposed slopes on Saturday afternoon.

Otherwise, recent avalanche activity around and north of Duffey Lake has been limited to loose dry sluffing and small human triggered soft slabs in the recent storm snow. This MIN is a great reminder that terrain traps can increase the consequences of even small avalanches. Glad everyone is unharmed.

Reports from the Coquihalla indicate quite limited natural storm slab activity during the storm with only a couple of size 2's noted near Hope.

Snowpack Summary

Recent storm snow has been variable across the region, the Coquihalla receiving around 60-80 cm and other areas in the 15-30 cm range. This snow appears to be bonding well to underlying surfaces including a sun crust on steep solar aspects and a rain crust below 1500 m in the Coquihalla area.

At upper elevations, recent snow is wind affected and is likely undergoing continued transport as winds pick up into Sunday morning. Wind direction has been predominantly westerly but may also may have southerly or northerly components, depending on elevation.

A weak layer composed of a crust, facets or surface hoar depending on elevation/aspect is now down 70-120 cm. This layer, buried in late January, continues to be noted in snowpack tests with mixed results. There have been no recent avalanches reported on this layer. Large triggers, such as an avalanche in motion, cornice fall, or intense loading from snow/ wind and/or a rapid rise in temperature can awaken these deeper weak layers.

The lower snowpack is well settled and strong in most areas.

Terrain and Travel

  • Wind slabs are most reactive during their formation.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.

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.