Storm slabs have been touchy and likely remain sensitive to human triggers. The most likely place to trigger an avalanche is in wind loaded terrain features at upper elevations.
A weak layer of faceted grains above a hard melt-freeze crust may be found around 50-80 cm deep. Last week this layer produced large avalanches. The problem was most prevalent on north to northeast aspects between 1600 m and 2100 m.
Storm slabs have been touchy, showing wide propagation. They are most likely to be triggered in deeper deposits of freshly wind loaded snow or in wind-sheltered areas where they sit over a weak layer of facets or surface hoar.
Tuesday night: Snowfall 5-10 cm, 20-30 km/h southwest wind, alpine temperature -6 C. Freezing level 1000 m.
Wednesday: Flurries 1-3 cm, 20 km/h southwest wind, treeline temperature -6 C. Freezing level 1300 m.
Thursday: Snowfall 5-15 cm, 30-40 km/h south wind, treeline temperature -5 C. Freezing level 1300 m.
Friday: Snowfall around 5 cm, 30-40 km/h south wind, treeline temperature -5 C. Freezing level 1300 m.
Storm slabs were touchy in the Whistler area on Monday and Tuesday. Natural, explosive, skier controlled and skier accidental storm slab avalanches were size 1-2, showing wide propagation. A few were triggered remotely or sympathetically. See photos in these MIN reports (1, 2) from the Whistler backcountry.
Persistent slab activity has dwindled since last week. The most recent activity was on Tuesday when two avalanches were triggered by riders on northeast aspects at treeline and alpine elevations, similar to the trend of previous avalanches. We are awaiting observations from the recent storm cycle to indicate whether it remains possible that humans or storm slab avalanches could trigger this layer, where it exists.
New snow has been wind loaded into soft slabs in lee terrain features at upper elevations. 30-60 cm of new snow has accumulated over variable surfaces including surface hoar in shady, wind-sheltered areas a hard melt-freeze crust found on all aspects below 1500 m and on sun-exposed slopes into the alpine.
Around 50 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 been most prevalent on north to northeast aspects between 1600 m and 2100 m. Check out this forecaster blog for more info. We are still awaiting observations from the current storm which will provide us with feedback on the reactivity of this layer going forward.
There are no deeper concerns at this time.
