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Avalanche Forecast

Archived

Mar 14th, 2023–Mar 15th, 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 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, Birkenhead, Duffey, South Chilcotin, Stein, Taseko.

Storm slabs may continue to be reactive on Wednesday, especially on leeward wind-loaded slopes. Use conservative decision-making if you notice signs of instability.The March sun packs a punch and can quickly destabilize the snowpack on solar slopes.

Confidence

Moderate

Avalanche Summary

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.

On Saturday there were reports of two wind slab avalanches. One was triggered by a rider and the other one went naturally. These occurred in the alpine on north to northeast aspects and at a depth of 20 to 25 cm.

Natural avalanche activity may occur throughout the week with rising freezing levels and solar radiation. Wind slabs may continue to be reactive to rider triggering.

Snowpack Summary

30 to 50 cm of storm snow has blanketed the region since last Friday. 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. A sun crust may exist below this new snow on steep solar aspects. In sheltered areas, this new snow will rest on various amounts of low-density snow that fell earlier in the week.

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

Tuesday Night

Cloudy, 3 cm of new snow. Alpine temperatures near -11. Winds southwest 20 to 45 km/h, with the freezing level at valley bottom.

Wednesday

A mix of sun and cloud. Alpine temperatures near -9. Winds southwest 15 to 40 km/hr gusts. Freezing level at valley bottom.

Thursday

A mix of sun and cloud. Alpine temperatures near -5. Wind light from the southeast. Freezing level 1500 m.

Friday

A mix of sun and cloud. Winds 10-20 km/hr from the southeast. Alpine temperatures near -2 with freezing levels 1800 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet

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.