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Avalanche Forecast

Archived

Dec 12th, 2021–Dec 13th, 2021

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

Cariboos.

Wind slabs will be the main concern on Monday. Be on the lookout for drifted snow and signs of instability like shooting cracks as you enter wind-affected terrain.

Confidence

Low - Uncertainty is due to the limited number of field observations.

Weather Forecast

Sunday night: A trace of new snow. Moderate southerly wind. Treeline temperatures around -10 C.

Monday: A mix of sun and cloud with isolated flurries up to 5 cm. Light to moderate southeast wind. Treeline temperatures around -9 C.

Tuesday: A mix of sun and cloud. Light northwest wind. Treeline temperatures around -15 C.

Wednesday: A mix of sun and cloud. Light southeast wind. Treeline temperatures around -13 C.

Avalanche Summary

Check out this MIN report, describing low elevation wind loading and touchy conditions near Barkerville on Sunday. We have not received reports of any other avalanche activity in the region.

There were two human triggered avalanches involving persistent weak layers last week. One was a size 2 avalanche triggered in a north-facing bowl near Barkerville. This avalanche is suspected to have occurred on a 50 cm deep surface hoar layer. The other was triggered near McBride and released on a steep rocky slope near treeline (see this MIN report). The failure layer was likely an early season crust/facet layer.

Snowpack Summary

The convective nature of the storm on the weekend has resulted in highly variable snowfall amounts throughout the region, generally ranging from 10-25 cm. While we don't have any recent observations from the alpine, we expect to see lots of redistribution of recent snow by wind, as wind loading was observed even at low elevations in the trees in this MIN report from near Barkerville on Sunday.

A few potentially concerning layers exist in the mid to lower snowpack. A surface hoar layer observed near Barkerville, and a widespread crust below 1800 m both now sit 40-70 cm deep. An early season crust layer with some weak snow around it can be found 100-250 cm deep in the alpine.

Terrain and Travel

  • Be careful as you transition into wind affected terrain.
  • Start on smaller terrain features and gather information before committing to bigger terrain.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.