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Avalanche Forecast

Archived

Mar 7th, 2022–Mar 8th, 2022

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

Regions

Purcells.

Watch for isolated pockets of wind slab in the alpine. Though stability is improving, it remains possible to trigger avalanches on a recently buried weak layer.

Confidence

High - Confidence is due to a stable weather pattern with little change expected.

Weather Forecast

Freezing levels drop to valley bottom for the forecast period as an arctic airmass overtakes the region.

Monday: Flurries bringing around 5 cm. Light to moderate northwest wind. Alpine temperature around -10 °C. Freezing level dropping to valley bottom. 

Tuesday: Flurries bringing 5-10 cm. Light easterly wind. Alpine high around -12 °C.

Wednesday: Mostly sunny. Light easterly wind. Alpine temperatures around -15 °C.

Thursday: A mix of sun and cloud. Moderate northwest wind. Alpine temperatures around -8 °C.

Avalanche Summary

Natural and explosive triggered cornices up to size 3 were reported on sunny Sunday.

Other solar induced natural activity over the weekend included loose dry up to size 1.5 and a size 2 storm slab.

Following a natural avalanche cycle up to size 2 during the storm earlier in the week, storm snow was touchy on Friday, with several rider triggered storm slab and loose dry avalanches around the region, including this remotely triggered size 1.5 near Golden.

Warm temperatures Thursday through Sunday are suspected to have sensitized buried weak layers such that explosive control work was able to trigger a few deep avalanches:

  • On Sunday explosive work near Panorama triggered size 1.5-2 avalanches on a buried weak layer from mid February up to 40 cm deep. Another round on Monday produced size 1-1.5s on the same layer but showing less propagation. 
  • On Friday in the Bugaboos, large explosives triggered several very large avalanches, mostly on northerly aspects in the alpine, including one size 3.5 with a crown 60-200 cm deep.
  • Check out this MIN report from Golden of a mysterious size 2 slab avalanche around treeline, suspected to have slid on the February weak layer.

Snowpack Summary

Surface snow has likely seen some redistribution by recent wind in the alpine. A few crusts may be found in and amongst the 30-60 cm of recent snow including a sun crust at the surface on solar aspects and an embedded melt freeze crust up to 1700 m on all aspects. The recent snow may also be sitting on an older sun crust on solar aspects, as well as weak surface hoar and faceted crystals on shaded aspects.

An interface from mid-February composed of sun crust and/or surface hoar is now 30-90 cm deep. Explosive work near Invermere (where it is 30-60 cm deep) on Sunday confirmed that this layer can still be triggered by large loads.

A layer of surface hoar from late January has not produced recent avalanche activity but crystals can still be identified 40-50 cm deep near Golden.

Terrain and Travel

  • Recent new snow may be hiding windslabs that were easily visible before the snow fell.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Small avalanches can have serious consequences in extreme terrain. Carefully evaluate your line for wind slab hazard before you commit to it.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.