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Avalanche Forecast

Archived

Mar 7th, 2021–Mar 8th, 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, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Cariboos.

 Watch for new wind slab development at upper elevations. A persistent slab problem is still a consideration in sheltered terrain.

Confidence

Moderate - Uncertainty is due to limitations in the field data.

Weather Forecast

SUNDAY Night: Cloudy with scattered flurries, accumulation 1-5 cm. Light to moderate southwest wind. Alpine high temperatures around -7 C. Freezing level at valley bottom.

MONDAY: Mix of sun and cloud. Light west and southwest wind. Alpine high temperature -4. Freezing level 1400 m.

TUESDAY: A mix of sun and cloud. Light west and southwest wind. Alpine high temperature -5. Freezing level 1400 m.

WEDNESDAY: Cloudy with sunny breaks and isolated flurries. Light to moderate northwest wind. Alpine high temperature -6. Freezing level 1300 m.

Avalanche Summary

Avalanche observations from the past week are limited to some reports of natural avalanches in the Barkerville area on Wednesday. Warm sunny weather likely caused a cycle of wet loose avalanches over the past few days.

Given the lack of recent field observations we remain uncertain about the likelihood of persistent slab avalanches. Since there was significant activity on these layers between Feb 23-28, we recommended remaining cautious because these types of weaknesses can take a long time to heal. Only consider pushing into bigger, steeper avalanche terrain if you are equipped to rule out the possibility of deeper weak layers in your local riding area.

Snowpack Summary

Up to 10 cm of new snow has accumulated above moist and crusty interfaces that formed during last Thursday's warm up. Deeper accumulations can be expected in lee terrain features as a result of southwest winds. High, shaded terrain will have a mix of soft snow and some old buried wind slabs.

In the last week of February multiple weak layers produced large avalanches, but we have little to no information about how these layers have trended since then. Recent weather patterns have likely helped these layers strengthen, but uncertainties are high. 

Layers of concern include a 50-100 cm deep layer of facets that was buried in mid-February, a 50-150 cm deep layer of surface hoar from early February that was most prevalent at treeline (and existed as a facet/crust combination on steep south-facing terrain), and finally another persistent weak layer from late January that is now roughly 100-150 cm deep.

Terrain and Travel

  • Be careful as you transition into wind affected terrain.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.

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.