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Avalanche Forecast

Archived

Feb 17th, 2023–Feb 18th, 2023

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

Regions

North Columbia, South Columbia, Esplanade, Jordan, North Selkirk, Shuswap, Badshot-Battle, Central Selkirk, Goat, Gold, Kokanee, North Okanagan, Retallack, Valhalla, Whatshan.

As the recent storm snow begins to consolidate into a slab, natural and human triggering becomes more likely. Select lower-angle terrain and avoid exposure to large paths and overhead hazards like cornices.

Confidence

Moderate

Avalanche Summary

Several loose dry avalanches were reported with sluff management being a consideration throughout the day.

Touchy storm slabs up to size 1.5 were reported as snowfall accumulated through Thursday.

Looking forward storm snow will need some time to settle and stabilize and may be particularly touchy where new snow has buried a surface hoar layer that developed earlier in the week. Wind slabs will likely develop at upper elevations throughout the day as another system travels through the region bringing variable winds.

Snowpack Summary

Another 10 to 15 cm of new snow overnight brings recent snowfall totals of 50 to 65 cm of low-density snow. New snow is forming storm slabs that may be more reactive where they have settled on a surface hoar layer that developed earlier this week.

Moderate variable winds throughout the day will be redistributing new snow into wind slabs at treeline and alpine elevations. Cornices continue to build new overhanging edges with this new snow and winds.

The mid-pack is generally well consolidated with a few operations reporting continued snowpack results on a spotty surface hoar layer down roughly 80 cm. Reports of large avalanches involving various layers of surface hoar/crusts and facets within the mid-pack depth are sporadic but are a reminder of the complicated snowpack across this region.

In the lower snowpack, a layer of large and weak facets from November near the base of the snowpack is slowly gaining strength but there continues to be low confidence in this layer. Large destructive avalanches are the result of this layer being triggered.

Weather Summary

Friday night

Mainly cloudy with snowfall, 5 to 10 cm accumulation, 15 to 20 km/h southwest winds, treeline temperatures -8 °C.

Saturday

Mainly cloudy, flurries with 5 to 10 cm accumulation, 20 to 30 km/h west winds, treeline temperatures -7 °C.

Sunday

Cloudy with flurries, 15 to 20 cm accumulation, 15 to 20 km/h southwest winds, treeline temperatures -6 °C.

Monday

Cloudy with flurries, 5 to 10 cm accumulation, 15 to 20 km/h westerly winds, treeline temperatures -8 °C.

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.
  • Don't let the desire for deep powder pull you into high consequence terrain.
  • Minimize exposure during periods of heavy loading from new snow and wind.

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.

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.