Avalanche Forecast
Regions: Northwest Coastal.
Natural and rider-triggered cornice and wind slab avalanches are the main concern. We are uncertain as to whether buried weak layers remain reactive but step-downs could quickly amplify the consequences of shallower releases.
Confidence
Low -
Weather Forecast
Thursday night: Flurries up to 5 cm. Moderate to strong southeast wind. Alpine low around -7 °C. Freezing level dropping to 800 m.
Friday: Flurries up to 5 cm. Moderate south wind easing through the day. Alpine high around -5 °C. Freezing level 1200 m.
Saturday: Flurries up to 5 cm. Light to moderate southeast wind. Alpine high around -5 °C. Freezing level 1100 m.
Sunday: Overnight flurries up to 5 cm then clearing. Light wind. Alpine high around -4 °C. Freezing level 1300 m.
Avalanche Summary
On Thursday, large (size 3) cornices were triggered by explosives. Natural and explosive triggered wind slabs were observed to size 1.5.
Touchy avalanche conditions on Wednesday saw skiers and machines remotely triggering storm slabs size 1.5-2. We're scratching our heads over a report from near Ningunsaw of a skier-triggered size 2.5 and sympathetic size 2 deep persistent slab. The avalanches occurred on a west aspect around 1200 m and crown depths varied from 40 cm to 120 cm.
A widespread natural avalanche cycle occurred on Tuesday. Storm slabs and loose wet avalanches were reported up to size 3. Some of these avalanches stepped down to a persistent weak layer now buried 70-120 cm deep that was active leading up to the storm. While it is now likely too deep to be easily triggered by riders, it may remain triggerable by large loads such as cornices and avalanches.
Snowpack Summary
30-50 cm of recent snow has seen variable wind effect at upper elevations. Below 1500 m, recent snow tapers in depth and sits over a wet or crusty upper snowpack.
A weak layer of surface hoar buried 70-120 cm deep has become more difficult to trigger but recent avalanche observations indicate that it may continue to be problematic. A thick rain crust from mid-February 130-200 cm deep caps a well consolidated lower snowpack.
Terrain and Travel
- Uncertainty is best managed through conservative terrain choices at this time.
- Be especially cautious as you transition into wind affected terrain.
- Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
- When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
Avalanche Problems
Wind Slabs
Deep wind slabs may be touchy where recent wind loaded snow is poorly bonded to underlying surfaces. If triggered, wind slab avalanches have potential to step down to deeper layers.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood: Possible - Likely
Expected Size: 1.5 - 2.5
Persistent Slabs
We have uncertainty as to whether a layer of surface hoar buried 70-120 cm deep remains a problem. While it is now likely too deep to be easily triggered by riders, it may remain triggerable by large loads such as cornices and avalanches.
Aspects: North, North East, East.
Elevations: Alpine, Treeline.
Likelihood: Unlikely - Possible
Expected Size: 2 - 3.5