Avalanche Forecast

Archived

Nov 27th, 2019–Nov 28th, 2019

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.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Regions

Northwest Coastal.

The most likely place to trigger avalanches is where the wind has formed new slabs at higher elevations.

Confidence

Moderate - Uncertainty is due to the extreme variability of wind effect on the snowpack.

Weather Forecast

WEDNESDAY NIGHT: Clear, 40 km/h wind from the northeast, alpine temperatures drop to -12 C.

THURSDAY: Sunny, 20 km/h wind from the northeast, alpine high temperatures around -8 C.

FRIDAY: Sunny, light wind from the northeast, alpine high temperatures around -3 C.

SATURDAY: Sunny, light wind from the northeast, alpine high temperatures around -5 C.

Avalanche Summary

Last weekend's storm likely caused a widespread cycle of natural avalanches, but there have been few reports since then. Looking forward, avalanches may still be possible to trigger in any areas where the recent snow has buried a smooth surface and where wind has formed new slabs. Concern is reduced in areas where the snow depths have not yet reach the threshold for avalanches.

Snowpack Summary

Strong wind from the northeast has likely formed new wind slabs on west and south facing slopes at higher elevations. Last weekend's storm delivered much more snow in western parts of the region (e.g. 150 mm of precipitation at Shames and only 36 mm at Rosswood). Recent observations from Shames suggest this resulted in about 30 cm of snow at 750 m, 100 cm of snow at 1200 m, and likely over a metre of snow in the alpine (see this MIN report). While the storm snow has likely settled since then, there is still some uncertainty about how well it has bonded to crust that it buried.

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.