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Avalanche Forecast

Archived

Dec 22nd, 2017–Dec 23rd, 2017

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

Regions

Cariboos.

Where there is uncertainty in the snowpack, conservative terrain is the answer. Check out today's Forecaster's blog for tips on managing the spatial variability associated with our current persistent slab problem. LINK

Confidence

Moderate -

Weather Forecast

Saturday: A mix of sun and cloud. Moderate northwest winds. Alpine temperatures of -15.Sunday: Mainly sunny. Light north winds. Alpine temperatures of -14.Monday: A mix of sun and cloud with cloud increasing in the afternoon. Light northwest winds. Alpine temperatures around -16.

Avalanche Summary

Touchy conditions were reported from the North Thompson area of the Cariboos on Wednesday, where steep banks in lower elevation cutblocks were observed releasing very easily with sled traffic. In the adjacent North Monashees, natural wind slab and storm slab releases were reported up to Size 2.5. Human-triggered slab avalanche potential can be expected to persist as our recent snow consolidates into a slab above the range of weak surfaces present at the December 15 interface. Please submit your observations to the Mountain Information Network (MIN).

Snowpack Summary

Stormy weather over the past week has brought 20-40cm of new snow to the region. The new snow lies over a wide variety of old surfaces, including large surface hoar (weak, feather-like crystals), hard crusts formed by sun or wind, and sugary facets. The bond at this old snow interface becomes critical as the overlying snow gradually consolidates into a slab. The most concerning areas areas will be those that have seen previous surface hoar development, such as sheltered areas at and below tree line and sheltered northerly aspects in the alpine. Additionally, any steep solar aspects where surface hoar may be sitting on sun crust should be considered areas where this weak layer may be more likely to trigger. A crust which was formed by rain in late November is a major feature in the snowpack and is down approximately 70-100cm at tree line elevations. Snowpack tests suggest the snow above is currently bonding well to it. Snowpack depth decreases rapidly below tree line. Look out for early season hazards such as rocks, stumps, and open creeks.

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.