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Avalanche Forecast

Archived

Feb 1st, 2023–Feb 2nd, 2023

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

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

A good day to avoid avalanche terrain. Reactive storm slabs are widespread and sit above a complex snowpack increasing the likelihood of triggering large, destructive avalanches over the coming days.

Confidence

Moderate

Avalanche Summary

Avalanche activity will likely spike Thursday as the temperatures slightly warm and the winds ramp up, redistributing and consolidating the 60-80 cm of recent storm snow.

On Wednesday the AvCan field team reported a snowmobile-triggered storm slab size 1 from a southwest aspect.

Very few avalanche reports came in on Tuesday. The recent storm snow formed very soft storm slabs with one report of size 1.5 natural. Loose-dry avalanches up to size 1 were seen from steep terrain features.

Last weekend, several very large (size 3 to 4) avalanches were triggered naturally on the basal facets. The avalanches were on all aspects and generally in alpine terrain between 2400 and 2900 m. See here for a video of a rider-triggered avalanche near Renshaw and another example here near Clearwater.

These avalanches are similar to what we've seen over the past week, with persistent and deep persistent avalanches releasing on the weak layers described in the Snowpack Summary. Most avalanches over the past week were large to very large (size 2 to 4), occurring between 1700 and 2400 m and on all aspects.

See more on the potential of triggering deeper weak layers Forecasters' Blog.

Snowpack Summary

60-80 cm of recent low-density storm snow has blanketed the region. The new snow accompanied by strong gusty winds on Thursday will likely form reactive storm slabs and wind slabs in lee terrain features. They will overly previously wind-affected snow from recent northeast wind.

Two layers of surface hoar crystals and/or a melt-freeze crust may be found around 30 to 80 cm deep. Surface hoar is most likely found in wind-sheltered terrain 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, which continue to produce very large avalanches in the region.

Weather Summary

Wednesday Night

Cloudy with snowfall, accumulation 10 to 15 cm with local enhancements possible. Ridgetop winds 30-40 km/h from the southwest. Treeline temperature -8 °C.

Thursday

Cloudy with lingering flurries in some areas and possible sunny breaks. Ridgetop wind 35 km/h and gusting to 65 km/h from the southwest. Treeline temperature -5 °C and freezing level 1100m.

Friday

Cloudy with light snow 5-10 cm. Ridgetop wind 30-45 km/h from the South. Treeline temperatures near -4 °C and freezing level 1200 m.

Saturday

Cloudy with snowfall, accumulation 5 to 10 cm. Ridgetop wind 25-45 km/h from the southwest. Treeline temperatures warming to -6 °C and freezing level 1000 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
  • Be mindful that deep instabilities are still present and have produced recent large avalanches.
  • 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.

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.