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Avalanche Forecast

Archived

Nov 25th, 2019–Nov 26th, 2019

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

Northwest Coastal.

The bond of our recent snow to the old surface remains in question. Expect wind-loaded areas to remain problematic even as the new snow gradually stabilizes.

Confidence

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

Weather Forecast

Monday night: Cloudy with isolated flurries and a trace of new snow. Light northwest winds.

Tuesday: Mainly sunny. Light to moderate northeast winds increasing over the day. Alpine high temperatures around -10.

Wednesday: Sunny. Moderate to strong northeast winds. Alpine high temperatures around -14

Thursday: Sunny. Light to moderate northeast winds easing over the day. Alpine high temperatures around -7.

Avalanche Summary

Avalanche observations from the succession of storms that impacted the region have yet to come in, but it is expected that the significant load of new snow (along with strong winds) promoted widespread natural storm slab avalanches at higher elevations, especially where new snow buried crust on the previous snow surface.

Looking forward, clearing weather is likely to make travel in the mountains a more inviting prospect, however this is a time to be on high alert in any areas where new snow buried a smooth surface and where winds have formed new slabs. Concern is reduced in areas where the new snow hasn't yet overcome the depth of ground roughness.

Snowpack Summary

Recent observations show that the succession of storms over the weekend covered bare ground with 30 cm of new snow at around 750 metres and 90 cm at around 1200 metres. With precipitation amounts totaling over 150 mm at Shames, there's a strong possibility of well over a metre of new snow at high alpine elevations. 

At these higher elevations, the new snow buried a melt-freeze crust which caps 30-40 cm of older storm snow. 

A heavy coastal focus was noted in precipitation amounts, with only 36 mm of rain recorded at Rosswood. 

Beyond the sheer quantity of new load in more coastal alpine areas (easily tripling the previous snowpack depth), the bond between the new snow and the old melt-freeze crust will remain in question for a few days. Forecast cool temperatures are expected to contribute to a slow bonding process.

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.