Avalanche Forecast
Regions: Coquihalla, Harrison-Fraser, Manning, Skagit.
Overnight winds from the northeast may form fresh wind slabs on unexpected slopes. Wind slabs may remain sensitive to human triggering, particularly in wind-loaded areas.
Take a cautious approach and investigate the bond between the new snow and the old surface before committing to your line.
Confidence
Moderate
Avalanche Summary
On Monday, one size 1.5 natural storm slab was observed from a distance on a steep treeline convex roll, and a natural glide slab released size 2 from a south aspect at 1600 m and ran 300 m in length.
Looking forward to Wednesday, human-triggered storm slabs remain likely, especially in wind-loaded areas. Storm slab reactivity is expected to persist for longer than is typical due to the weak surface they are sitting on.
Please continue to post your reports and photos to the Mountain Information Network.
Snowpack Summary
Last weekend's 15-30 cm of new snow may have a poor bond to the underlying surface, consisting of stiff wind slabs and near-surface faceting formed by recent wind and cold temperatures.
A melt-freeze crust formed in mid-January is buried up to 90-140 cm deep. In some areas, small faceted crystals can be found above the crust. This layer has been reactive during the storm Tuesday night and Wednesday this week. The snow below this layer is well consolidated.
Snowpack depths are just below seasonal averages. Total amounts range from 150 to 300 cm at treeline, but decreases significantly below 1500 m.
Weather Summary
Tuesday Night
Clear periods. Alpine temperatures -8 °C. Ridge wind northeast 15 km/h. Freezing level valley bottom.
Wednesday
Cloudy with flurries up to 5 cm. of accumulation Alpine temperatures reach a high of -7 °C. Southwest wind 40 km/h and freezing level valley bottom.
Thursday
Snow amounts 15-25 cm. Ridgetop wind 40-70 km/h from the southwest. Alpine temperatures reach a high of -5 °C. Freezing level 600 m.
Friday
Cloudy with snow 5-10 cm. Alpine temperatures near -6°C. Ridge wind southwest 25 gusting to 50 km/h. Freezing level 500 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Recent wind has varied in direction so watch for wind slabs on all aspects.
- Seek out sheltered terrain where new snow hasn't been wind-affected.
- Carefully monitor the bond between the new snow and old surface.
- Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
Avalanche Problems
Wind Slabs
Up to 30 cm of storm snow fell last weekend and has been redistributed by southwest winds into wind slabs in lee areas. Changing winds overnight Tuesday may form new wind slabs on opposite slopes and terrain features. In many areas, this new snow may be bonding poorly to the underlying surface and storm slab reactivity may persist for longer than is typical.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible - Likely
Expected Size: 1 - 2.5
Persistent Slabs
A crust formed in mid-January can be found down 80 to 120 cm. In areas around the Coquihalla, facets can be found sitting on the crust. This layer is of greatest concern with large triggers, such as a cornice fall, or by first triggering a smaller avalanche that could step down to this interface.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Unlikely - Possible
Expected Size: 1 - 3