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Avalanche Forecast

Archived

Mar 6th, 2023–Mar 7th, 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

Coquihalla, Harrison-Fraser, Manning, Skagit.

Wind slabs may remain reactive on a variety of aspects at treeline and above.

Sheltered terrain at lower elevations will likely offer the best and safest riding.

Confidence

Moderate

Avalanche Summary

A naturally triggered glide slab avalanche was reported on a west aspect on Sunday.

On Saturday, explosive avalanche control work resulted in numerous very large avalanches. They included storm, persistent, and deep persistent slab avalanches and were size 3-4. They initiated on a variety of aspects in the alpine.

Snowpack Summary

Up to 100 cm of snow last week and shifting strong winds formed wind slabs on a variety of aspects at treeline and above. These slabs are sitting on either hard surfaces or small facets.

A melt-freeze crust formed in mid-January is buried up to 170 to 190 cm deep at treeline and above. Though still a concern, it appears to be gaining strength.

Weather Summary

Monday Night

Partly cloudy / Light south ridgetop wind / Low temperature at treeline -13 C / Freezing level valley bottom.

Tuesday

Mix of sun and cloud / Light southeast ridgetop wind / High temperature at treeline -2 C / Freezing level 1100 m.

Wednesday

Mix of sun and cloud / Light southeast ridgetop wind / High temperature at treeline -2 C / Freezing level 1200 m.

Thursday

Mix of sun and cloud / Moderate southeast ridgetop wind / High temperature at treeline -3 C / Freezing level 1100 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be especially cautious as you transition into wind affected terrain.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.
  • Sheltered low elevation terrain will likely offer the best and safest riding today.
  • Avoid exposure to slopes that have cornices overhead.

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.