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Avalanche Forecast

Archived

Mar 15th, 2023–Mar 16th, 2023

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

South Coast Inland, Birkenhead, Duffey, South Chilcotin, Stein, Taseko.

The March sun packs a punch and can quickly destabilize the snowpack on solar slopes.Storm slabs may continue to be reactive to human triggering, especially on leeward wind-loaded slopes.

Confidence

Moderate

Avalanche Summary

No new reports on Wednesday at the time of publishing.

On Tuesday, several skier-controlled slab avalanches (size 1.5) were reported on wind-loaded features at treeline and above. Dry loose sluffing was noted from steep northeast terrain up to size 1.5.

On Monday, several natural cornice falls were reported in the northern part of the region up to size 2.5.

On Sunday, a natural large size three, wind slab avalanche was observed. It started in a cross-loaded feature in the alpine and it may have stepped down to weaker buried layers.

Natural and human-triggered avalanche activity may occur throughout the week with rising freezing levels and solar radiation.

Snowpack Summary

Surface snow will likely become moist on solar aspects during the day. 30 to 50 cm of recent storm snow sits above a sun crust on steep solar aspects, dryer low-density snow, and older faceted snow in sheltered areas. Much of this has been redistributed into reactive wind slabs at treeline and above. It has also built upon the large cornices that have already formed.

The mid-snowpack is well consolidated.

There is a widespread weak layer of large sugary facets at the bottom of the snowpack. Recent avalanche activity on this layer has been confined to northern parts of the region in the Chilcotins. This layer remains a concern in shallow snowpack areas.

Weather Summary

Wednesday Night

Clear. Alpine temperatures near -11. Wind from the west 10 km/hr and freezing level valley bottom.

Thursday

A mix of sun. Alpine temperatures near -4. Winds southeast 10-20 km/hr. Freezing level 1600 m.

Friday

A mix of sun and cloud. Alpine temperatures near -3. Wind southeast 10-20 km/hr. Freezing level 1800 m.

Saturday

A mix of sun and cloud. Winds 10-20 km/hr from the south. Alpine temperatures near -2 with freezing levels 1900 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.