The arctic air is arriving. Dial back trip plans to easier, shorter trips and watch for unusual wind loading patterns from north winds. See our Forecasters' Blog for more on managing the cold.
Watch for signs of slab formation in the new snow, particularly in wind-affected areas and where buried surface hoar could be preserved (think sheltered openings at mid elevations).
Basal facets remain a real concern in steep, rocky terrain and other alpine features with thin-to-thick snowpack transitions. Recent avalanche activity tells us this problem is still lurking out there.
Tuesday was likely a busy day for natural and human-triggerable avalanches as moderate to heavy snowfall and elevated winds affected the region.
A size 2 (large) deep persistent slab was triggered from a 20 m distance in the Clemina alpine on Sunday on a NE aspect. It was 70 cm deep, failing at the base of the snowpack. This highlights the problematic basal snowpack structure in the region.
Aspects lee to north winds are a concern for the most recent or new wind slab formation.
Roughly 30-40 cm of new snow fell in the region Monday night through Tuesday. It buried moderately wind-affected snow in exposed areas at elevation and otherwise added to about 50 cm of recent storm snow.
All this snow collectively overlies a variety of old surfaces, but sheltered terrain where it may overlie preserved surface hoar is the most concerning. It overlies a crust below about 1600 m.
Two additional surface hoar layers in the top 2 m of the snowpack are diminishing in importance. The deeper of the two likely has a robust crust above it below treeline.
The depth of the snowpack varies greatly throughout the region and weak basal facets are present at the base of the snowpack.
Wednesday night
Clearing, still mainly cloudy. Northwest alpine wind 5-15 km/h. Treeline temperature -16°C.
Thursday
Mainly sunny or thin overcast. Northeast wind 10-25 km/h, increasing overnight. Treeline temperature -29°C.
Friday
Sunny. North Alpine wind 5-10 km/h. Treeline temperature -30°C to -35°C.
Saturday
Sunny. Variable alpine wind 5-10 km/h. Treeline temperature -30°C to -35°C.
More details can be found in the Mountain Weather Forecast.
