Avalanche Forecast
Regions: Sea To Sky.
A buried weak layer remains triggerable and now new snow and wind are forming fresh wind slabs at upper elevations. Check back in the morning for potential updates based on overnight snowfall.
Confidence
Moderate - Forecast snowfall amounts are uncertain.
Weather Forecast
A weak flow will produce a tight east-to west gradient for snowfall amounts on Saturday. Areas coastal to Squamish may receive upwards of 20 cm by the end of Saturday while inland of Whistler may see less than 5 cm.
Friday night: Cloudy with snowfall, accumulation 5-15 cm, 30-50 km/h southwest wind, alpine temperature -7 C.
Saturday: Cloudy with snowfall, accumulation around 5 cm, 20-30 km/h south wind, alpine temperature -6 C. Freezing level 1500 m.
Sunday: Overnight snowfall 5-10 cm then cloudy with sunny periods, 10-20 km/h southwest wind, alpine temperature -5 C. Freezing level 1500 m.
Monday: Cloudy with snowfall, accumulation 20-40 cm, 40-60 km/h southwest wind, alpine temperature -3 C. Freezing level 1500 m.
Avalanche Summary
No new avalanches were reported on Wednesday or Thursday. Two more persistent slab avalanches were triggered by riders on Tuesday. They occurred at treeline and alpine elevations on a northeast aspect, similar to the trend of previous avalanches. It remains possible that humans could trigger this layer, where it exists.
Looking forward, new wind slabs will continue to grow over the day. Steep, lee terrain features should be entered cautiously.
Snowpack Summary
New snow and strong southwest wind are forming new wind slabs in lee terrain features. 10-20 cm are expected by Saturday evening. The snow builds on a thin layer of variably wind affected, faceted snow or surface hoar that overlies a hard melt-freeze crust found on all aspects below around 1500 m and on sun-exposed slopes into the alpine. The snow falls onto previously wind-affected and faceted snow on shaded slopes above 1500 m.
Around 40 to 80 cm deep, a weak layer of sugary faceted grains may be found above a melt-freeze crust that formed in February. This layer has produced about one or two human-triggered avalanches per day over the past week. Activity has been most prevalent on north to northeast aspects between 1600 m and 2100 m. Check out this forecaster blog for more info.
There are no deeper concerns at this time.
Terrain and Travel
- Dial back your terrain choices if you are seeing more than 20 cm of new snow.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Closely monitor how the new snow is bonding to the old surface.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
- Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
Avalanche Problems
Wind Slabs
New snow and southwest will likely form wind slabs in lee terrain features. The slabs will grow over the day and may not bond well to underlying layers.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 1.5
Persistent Slabs
A weak layer of faceted grains above a hard melt-freeze crust may be found around 40 to 80 cm deep. This layer continues to produce large avalanches that have the potential to propagate far. The problem is most prevalent on north to northeast aspects between 1600 m and 2100 m.
Aspects: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1.5 - 2.5