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Avalanche Forecast

Archived

Nov 30th, 2022–Dec 1st, 2022

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

Regions

Cariboos, North Rockies, McBride, Premier, Quesnel, Sugarbowl, Kakwa, McGregor, Pine Pass, Renshaw, Robson, Tumbler.

Increasing and strong north winds are transporting a lot of light and dry snow, and wind slabs are building! The avalanche danger is heightened in the alpine.

Confidence

Moderate

Avalanche Summary

A helicopter explosive mission near Sukunka creek triggered a few size-one wind slab avalanches. One windslab size 2.5 (very large) was triggered with a large explosive on a south aspect at 2200 m. The avalanche was described as fast-moving, with the powder debris splitting onto two separate avalanches.

Reports from an observation flight on Monday over the Sentinel pass indicate that a past natural storm slab avalanche cycle occurred in steep rocky terrain only. Avalanches in this cycle were up to size 2.5 (very large).

Observation of windslabs naturally triggered have been reported on north aspect terrain between 1350 m and 1450 m, likely occurring on the reported melt-freeze crust.

Please consider sharing your observations via the Mountain Information Network to help us and fellow recreationists.

Snowpack Summary

The storm last week delivered to this region between 40 to 80 cm of new snow. Winds were strong from the southwest during this event, and terrain exposed to this wind has been stripped with new snow building into wind slabs on north aspects.

During the past storm event a period of warming brought rain up to nearly 1500 m and now a melt-freeze crust can be found down 70 cm.

During mid-November, a period of cooling temperatures created a weak layer above the 1200-meter mark and can be found down 80 cm.

Average snowfall depths are around 20 to 60 cm below the treeline and 100 to 120 cm in the alpine.

Weather Summary

Wednesday Night

Cloudy with very light flurries, accumulation 1 to 3 cm, 50 km/h northeast wind, treeline temperature -25 °C.

Thursday

Clear sky no forecast precipitation, 30 km/h northwest wind, treeline temperature -27 °C.

Friday

Clear sky no forecast precipitation, 10 km/h northwest wind, treeline temperature -27 °C.

Saturday

Mostly cloudy with very light flurries, accumulation 1 cm, 20 km/h southwest wind, treeline temperature -19 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Make observations and assess conditions continually as you travel.

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.

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.