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Avalanche Forecast

Archived

Feb 3rd, 2023–Feb 4th, 2023

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
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, McGregor, Renshaw, Robson.

Wind and warming combined with recent storm snow are creating dangerous avalanche conditions. Reactive storm slabs sit above a complex snowpack, increasing the likelihood of triggering large and destructive avalanches.

Confidence

Moderate

Avalanche Summary

Looking forward to Saturday, touchy storm slabs can be expected at all elevations as wind and warm temperatures form cohesive slabs in the upper storm snow. Deeply buried weak layers will be primed to produce large natural and human-triggered avalanches.

On Thursday, several natural and human-triggered storm and wind slabs were observed up to size 1.5. One large (size 3) deep persistent slab was observed on a north aspect in the alpine.

On Wednesday, numerous natural and rider-triggered storm slabs and dry loose avalanches were reported up to size 1.5.

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 1700 and 2900 m. See here for a video of a rider-triggered avalanche near Renshaw and another example here near Clearwater.

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

Snowpack Summary

50-90 cm of recent low-density storm snow has blanketed the region. Strong southwesterly winds and warming temperatures will likely form reactive storm slabs and wind slabs in lee terrain features. This 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, which continue to produce very large avalanches in the region.

Weather Summary

Friday night's storm snow accumulation will vary significantly across the region. The Monashees and southern Cariboos are looking like the hotspot, but there is uncertainty due to the convective nature of this storm.

Friday night

Mainly cloudy with periods of snow, heavy at times with accumulation varying from two to 15 cm. Alpine temperatures drop to a low of -6 °C. Ridge wind southwest 30-50 km/h. Freezing level 500 meters.

Saturday

A mix of sun and cloud with flurries, up to 5 cm of accumulation. Alpine temperatures reach a high of -4 °C. Ridge wind southwest 30-50 km/h. Freezing level 1400 meters.

Sunday

Cloudy with snowfall, two to 15 cm of accumulation. Alpine temperatures reach a high of -4 °C. Ridge wind southwest 25 km/h gusting to 60 km/h. Freezing level 1600 meters.

Monday

Mainly cloudy with snowfall, 5 to 15 cm of accumulation. Alpine temperatures reach a high of -5 °C. Ridge wind southwest 20-50 km/h. Freezing level 1300 meters.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be mindful that deep instabilities are still present and have produced recent large avalanches.
  • Good day to make conservative terrain choices.
  • Use increased caution at all elevations. Storm snow is forming touchy slabs.
  • Storm slabs in motion may step down to deeper layers resulting in 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.