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Avalanche Forecast

Archived

Mar 4th, 2023–Mar 5th, 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 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.

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

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 considered generally strong with a small surface hoar layer from mid February that appears to be spotty and is not producing avalanche activity.

A layer of large and weak 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

Saturday Night

Light easterly winds, gusting moderate. Freezing levels below valley bottom.

Sunday

A mix of sun and cloud. Light easterly winds. Freezing levels below valley bottom, alpine high of -8 °C.

Monday

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

Tuesday

Mostly cloudy with moderate southwest winds. Freezing levels below valley bottom, alpine high of -4 °C. Flurries.

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.