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Avalanche Forecast

Archived

Mar 15th, 2022–Mar 16th, 2022

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Sea To Sky.

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.

Confidence

High -

Weather Forecast

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.

Avalanche Summary

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.

Snowpack Summary

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.

Terrain and Travel

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.