Avalanche Forecast
Issued: Feb 3rd, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs, Deep Persistent Slabs and Persistent Slabs.
zryan,
Avalanche Canada
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.
Summary
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
This week's 50-90 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
Expected Size
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
Expected Size
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
Expected Size
Valid until: Feb 4th, 2023 4:00PM
