Avalanche Forecast

Issued: Feb 4th, 2023 4:00PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs, Deep Persistent Slabs and Persistent Slabs.

Avalanche Canada zryan, Avalanche Canada

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Ongoing snowfall in the past week has added significant load to a weak and volatile snowpack.

Reactive storm slabs may be evident underfoot, particularly in wind-loaded areas, but keep the potential for large, destructive deep persistent avalanches in the forefront of your mind.

Summary

Confidence

Moderate

Avalanche Summary

On Friday, numerous natural wind slabs were observed throughout the region (size 2-2.5). A few large natural deep persistent slabs were also observed in the alpine and treeline (size 2.5-4).

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.

High-consequence avalanche activity is ongoing for the past week. Your best defence is to stay diligent in choosing low-consequence terrain away from overhead exposure.

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 continue to form reactive storm slabs. 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

Saturday night

Mainly cloudy with scattered flurries, up to 5 cm accumulation. Alpine temperatures drop to a low of -5 °C. Ridge wind southwest 30-50 km/h. Freezing level 800 metres.

Sunday

Cloudy with snowfall, up to 10 cm accumulation. Alpine temperatures reach a high of -4 °C. Ridge wind west 25 km/h gusting to 65 km/h. Freezing level 1500 metres.

Monday

Cloudy with snowfall, up to 10 cm accumulation. Alpine temperatures reach a high of -5 °C. Ridge wind southwest 40-60 km/h. Freezing level 1300 metres.

Tuesday

Cloudy with snowfall, heavy at times, 5 to 15 cm of accumulation. Alpine temperatures reach a high of -4 °C. Ridge wind southwest 40-60 km/h. Freezing level 1500 metres.

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.
  • If triggered, storm slabs in-motion may step down to deeper layers and result in very large avalanches.
  • 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

An icon showing Storm Slabs

This week's 40-80 cm of storm snow combined with the strong southwesterly wind and warming temperatures will form reactive storm slabs, especially on leeward slopes that may see more loading from the wind. Dry loose avalanches and sluffing will occur from steep terrain.

Keep in mind that storm slabs have the potential to step down to deeper weak layers, resulting in large and consequential avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2.5

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

A layer of large and weak facets sits near the base of the snowpack. In the past week, this layer has produced very large avalanches that can travel far. Riders are most likely to trigger an avalanche on this layer in steep, shallow terrain, or by triggering a smaller avalanche that could step down to this layer.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 3.5

Persistent Slabs

An icon showing Persistent Slabs

Two surface hoar layers found in the upper 100 cm of the snowpack have been reactive in scattered areas around the region. Be especially cautious around steep openings within and near treeline elevations, especially where the recent storm snow has been wind affected.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1.5 - 2.5

Valid until: Feb 5th, 2023 4:00PM