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Avalanche Forecast

Archived

Mar 5th, 2023–Mar 6th, 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

Cariboos, Blue River, Clearwater, McBride, Premier, Quesnel, Sugarbowl, Clemina, North Monashee, Renshaw, Robson.

Don't let good visibility lure you into dangerous terrain. Avoid wind-loaded features at upper elevations and steer well clear of overhead cornices and sun-affected slopes during periods of strong solar radiation. The best and safest riding will be found in sheltered and shaded locations.

Check out the most recent Forecaster Blog for the latest on the deep persistent slab problem.

Confidence

Moderate

Avalanche Summary

On Thursday and Friday, storm and wind slabs were reported to size 2.5 from natural and human triggers. Operators reported rapid loading due to winds at higher elevations but observations have been limited due to visibility and weather. We expect a natural cycle to have occurred primarily in wind loaded features.

On Saturday, two size 1 skier-triggered wind slabs were reported from south-facing alpine terrain. Several natural storm slabs were also reported from south-facing alpine terrain, triggered by strong solar radiation.

The last deep persistent slab avalanches were observed over a week ago, occurring during the very windy arctic outflow event.

Read more about managing the deep persistent slab problem in our latest Forecaster Blog.

Snowpack Summary

Variable winds have redistributed recent storm snow into deeper deposits on many aspects. This storm snow sits over wind effected surfaces and a thin sun crust on steep south facing slopes.

Around 40-90 cm deep a layer of small surface hoar exists in lower elevation sheltered areas. Elsewhere heavily wind effected surfaces exist, with faceted (sugary) snow from the late February Arctic blast. Reports suggest this interface has not yet been reactive.

The remainder of the mid-snowpack is generally strong with a small surface hoar layer from mid February that appears to be spotty and is not producing avalanche activity.

A weak layer of facets that formed in November sits near the base of the snowpack. Although the likelihood of triggering this layer is low at this time, the consequence of doing so remains very high. This layer is most likely to be human-triggered in thin, rocky slopes at alpine and upper treeline elevations.

Weather Summary

Sunday night

Clear periods. Alpine temperatures drop to a low of -12 °C. Ridge wind light from the southeast. Freezing level at valley bottom.

Monday

A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -10 °C. Ridge wind light from the south. Freezing level at valley bottom.

Tuesday

A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -9 °C. Ridge wind south 15-35 km/h. Freezing level 800 meters.

Wednesday

Sunny with cloudy periods. Alpine temperatures reach a high of -8 °C. Ridge wind southeast 10-30 km/h. Freezing level 800 meters.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.

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.

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.