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Avalanche Forecast

Archived

Jan 8th, 2023–Jan 9th, 2023

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

Sea To Sky, Brandywine, Garibaldi, Homathko, Powell River, Spearhead, Tantalus, Sasquatch, Sky Pilot.

Forecast snow and wind overnight on Sunday are expected to form fresh storm slabs reactive to human triggers, especially in wind-affected terrain.

Choose conservative terrain and watch for clues of instability.

Confidence

Moderate

Avalanche Summary

Several small (size 1) human-triggered storm slabs were reported in the Brandywine and Whistler area on Saturday. These were intentionally triggered by skiers and failed within the recent storm snow on north-westerly slopes. Explosive controls also triggered slabs avalanches up to size 2 on immediate lee features around Whistler. The likelihood of avalanches will increase with the arrival of the forecast weather.

Snowpack Summary

Up to 25 cm of new snow has fallen into the region since Friday. Ongoing southerly and previous northerly winds have affected the storm snow in any open terrain and near ridgelines. On sheltered slopes, up to 50 cm of powder storm snow can be found. Snow is heavy and moist at lower elevations.

In sheltered terrain at treeline, a weak layer of surface hoar may still be buried under the storm snow down 30 to 50 cm. A thick crust formed in late December is down 40 to 70 cm. Professionals are concerned that avalanches may run down to this crust. At lower elevations, this crust is up to 15 cm thick. In the alpine, it is thin and breakable.

Near the base of the snowpack, a weak facet/crust layer from mid-November can be found and remains a concern. In general, the snowpack is weak, faceted, and shallow.

Weather Summary

A series of frontal bands will generate periods of moderate snowfalls Sunday night and Monday night. Overcast skies and dry conditions are expected Tuesday and Wednesday.

Sunday night

Snow 10-15 cm expected, moderate southerly winds gusting 45 km/h, freezing levels around 1000 m; low of -3C at treeline.

Monday

Cloudy with flurries up to 5 cm, moderate southerly winds gusting 45 km/h, freezing levels around 1200 m, high of -1C at treeline. Additional 15-20 cm overnight.

Tuesday

Cloudy; lingering flurries up to 5 cm, moderate southeasterly winds easing to light, freezing levels around 1500 m, high of +0C at treeline.

Wednesday

Cloudy, lingering flurries up to 5 cm, moderate southerly winds gusting 45 km/h, freezing levels around 1200 m, high of -2C at treeline. Additional 15-20 cm overnight.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

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.