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Avalanche Forecast

Archived

Mar 14th, 2022–Mar 15th, 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 possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Sea To Sky.

Fresh storms slabs have been touchy and will continue to grow deeper with new snow and wind Tuesday. Be aware of the potential for large avalanches due to the presence of a buried weak layer.

Confidence

High -

Weather Forecast

Monday night: Snowfall, accumulation 10-15 cm, 40-50 km/h southwest wind, alpine temperature -5 C. Freezing level 1100 m.

Tuesday: Snowfall 10-15 cm, 20-40 km/h southwest wind, alpine temperature -6 C. Freezing level 1300 m.

Wednesday: Overnight snowfall 5-10 cm then cloudy, 10-20 km/h southwest wind, treeline temperature -7 C. Freezing level 1300 m.

Thursday: Snowfall bringing 15-25 cm, 30-40 km/h south wind, treeline temperature -5 C. Freezing level 1300 m.

Avalanche Summary

Storm slabs were touchy on Monday. Explosive and skier control work produced size 1-2 storm slabs showing wide propagation, a few of which were triggered remotely or sympathetically.

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. 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

  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • Storm slab size and sensitivity to triggering will likely increase through the day.
  • 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.
  • Avoid areas with overhead hazard.

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.