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Avalanche Forecast

Archived

Mar 3rd, 2023–Mar 4th, 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

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

Avoid wind loaded features on all aspects, winds are expected to vary. Steer clear of sun affected slopes if skies clear, even short bursts of sunshine may increase reactivity.

Deep persistent weak layers continue to be a concern in this region. Read about managing this problem in our latest Forecasters' Blog.

Confidence

Moderate

Avalanche Summary

On Thursday storm slabs were reported human triggered to size 1. Natural avalanches were reported to size 2.5 thought to occur during heavy snowfall or wind loading. Operators reported rapid loading due to winds at higher elevations but observations were limited due to visibility and weather. We expect a natural cycle to have occurred, especially in wind loaded features and that human triggered avalanches were also likely.

A few very large (size 3.5 to 4) deep persistent slab avalanches were also observed over last week, which likely occurred during the very windy arctic outflow event.

Snowpack Summary

Storm totals have reached 30-80 cm. Variable winds have redistributed this into deeper deposits on many aspects. This storm snow sits over wind effected surfaces, a thin sun crust on steep south facing slopes.

Below this interface, around 50-90 cm deep, a layer of small surface hoar from exists in lower elevation sheltered areas and more widespread faceted (sugary) snow and heavy wind effect from the late February Arctic blast. Reports suggest this interface is beginning to bond and strengthen.

The remainder of the mid-snowpack is considered generally strong with a small surface hoar layer buried over 1 m deep from mid February. Reports suggest this layer is bonding well but most likely found around treeline elevations in areas sheltered from the wind.

Large and weak facets that formed in November are found 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

Friday Night

Cloudy with easing flurries. Light southwest winds. Freezing levels below valley bottom.

Saturday

A mix of sun and cloud. Light to moderate easterly winds. Freezing levels below valley bottom, alpine high of -6 °C.

Sunday

A mix of sun and cloud. Light to moderate east winds. Freezing levels below valley bottom, alpine high of -8 °C. Possible flurries.

Monday

Mostly cloudy. Moderate southerly winds. Freezing levels below valley bottom, alpine high of -5 °C. Flurries possible.

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.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.

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.

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.