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Avalanche Forecast

Archived

Feb 9th, 2023–Feb 10th, 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, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

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

Continue to choose conservative terrain and watch for signs of instability as strong winds continue to promote slab development in lees throughout the day.

Avoid shallow, rocky snowpack areas where triggering the deep persistent weak layer is still possible.

Confidence

Moderate

Avalanche Summary

On Wednesday, clearer weather allowed for observations at higher elevations. A widespread storm slab avalanche cycle from the past 24 to 48 hours was observed with avalanches from size 1.5 to 3. Most notable was a size 3 persistent slab avalanche that initiated on a steep north slope at 2000 m. The slab was 100-130 cm deep.

On Tuesday, a size one skier accidental avalanche was reported on a northwest feature below treeline.

On Sunday and Monday, several small natural wind slab avalanches were observed, up to size 1.5, at treeline on steep east-facing slopes.

Snowpack Summary

60-100 cm of storm snow from the last week continues to be redistributed by southwest winds. Storm snow sits above a plethora of old snow surfaces including previously wind-affected snow at upper elevations, a sun crust on steep solar aspects, faceted snow, and surface hoar crystals in wind-sheltered terrain.

In the upper meter of the snowpack sits two layers of surface hoar crystals and/or a melt-freeze crust. The surface hoar is most likely found around treeline and lower alpine elevations. The melt-freeze crust is found up to 1800 m on all aspects and into the alpine on sun-exposed slopes.

Large and weak facets from November are near the base of the snowpack and continue to produce very large avalanches in the region.

Weather Summary

Thursday Night

Cloudy with isolated flurries, 2-5 cm accumulation. Ridge wind from the southwest 40-60 km/h in the evening. Alpine temperatures rise to -3 C. Freezing level rises to 1200 meters.

Friday

Cloudy with sunny periods isolated flurries, 2-5 cm accumulation. Moderate southwest ridge wind switch to 20 km/h westerley winds mid-day. Alpine temperatures rise to -2 C. Freezing level rises to 1000 meters.

Saturday

Mix of sun and cloud with isolated flurries, 2-5 cm accumulation. West ridge wind 20 km/h gusting 40 km/h. Alpine temperatures rise to -3 C. Freezing level rises to 800 meters.

Sunday

Cloudy with scattered flurries, 5-10 cm accumulation. Ridge wind southwest 40-50 km/h. Alpine temperatures rise to -2 C. Freezing level rises to 1500 meters.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Stay off recently wind loaded slopes until they have had a chance to stabilize.
  • Be especially cautious as you transition into wind affected terrain.
  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

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.

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.