Avalanche Forecast
Issued: Feb 5th, 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.
lbaker,
Avalanche Canada
Southwest winds and warm temperatures are promoting slab cohesion and building reactive storm slabs in lees. Be especially cautious as you transition into wind-affected terrain and remember that if triggered storm slabs in motion could step down to deeper weak layers and result in very large avalanches.
Summary
Confidence
Avalanche Summary
On Saturday, a few small windslab avalanches were reported to be reactive to skier traffic at treeline. A natural wind slab avalanche, size 2, was reported on an east aspect at 2100 m.
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.
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 continue to build 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
Sunday Night
Mainly cloudy with clear periods and isolated flurries, trace accumulation. Alpine temperatures reach a high of -5 °C. Ridge wind northwest 25 km/h gusting to 65 km/h. Freezing levels fall to 500 m.
Monday
Mainly cloudy with isolated flurries in the afternoon, 2-7 cm accumulation. Alpine temperatures reach a high of -4 °C. Ridge wind southwest 40-60 km/h. Freezing level 1400 metres.
Overnight 5-10 cm accumulation, up to 15 cm in localized areas.
Tuesday
Cloudy with flurries, 5-10 cm of accumulation. Alpine temperatures reach a high of -4 °C. Ridge wind southwest 20-40 km/h. Freezing level 1500 metres.
Wednesday
Mix of sun and cloud with the possibility of light flurries, trace accumulation. Alpine temperatures rise to -7 C. Ridge wind west 20 km/h. Freezing level rises to 900 meters.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- 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 has formed reactive storm slabs. Use extra caution around leeward slopes where winds have formed deep storm slab pockets.
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 6th, 2023 4:00PM
