Watch for flurries and wind building slabs along ridges and lee features throughout Thursday. Bump the avalanche hazard to CONSIDERABLE in areas that accumulate over 20 cm of new snow. Weak basal facets are on the radar due to limited data and the high consequence of triggering.
Wind is redistributing new and loose snow, building slabs around ridgeline and lee features. Be especially wary around wind-loaded slopes in the alpine, triggering a wind slab avalanche here could step down to ground.
Weak snow at the base of the snowpack has produced a few recent avalanches. We need more information on the distribution of this layer but we suspect it only exists at high treeline elevations and into the alpine.
Wednesday night: Increasing clouds and isolated flurries, trace to 5 cm accumulation. Southwest winds 30-50 km/hr. Alpine temperature low -9C. Freezing level below 1000m.
Thursday: Flurries, trace to 10 cm accumulating by the end of the day. Southwest winds, 40-55 km/hr. Alpine temperature high -2C. Freezing level rising to 1400 m.
High elevations around the Bugaboos and western peaks of the Purcell forecast region could see enhanced precipitation accumulating up to 30 cm by the end of Thursday.
Friday: Flurries and snow, up to 15 cm. Southwest winds, 30-50 km/hr. Alpine temperature high -1C. Freezing level 1500m.
Saturday: Mostly cloudy with flurries. Southwest winds 15-30 km/hr. Alpine temperature high -1C. Freezing level 1400 m.
On Tuesday, November 23, explosives triggered a large (size 2) avalanche which failed on facets at the bottom of the snowpack. This was a reloaded slope (already avalanched this season) and occurred on a north aspect at 2270 m.
This MIN report captures a very large avalanche (size 3) at 2400m which failed at the ground. This avalanche occurred just east of the Purcell Forecast Region and is likely over 4 days old, but it brings attention to a possible weak basal layer that also exists in the Purcells at upper treeline and into the alpine.
On Monday, November 22, explosives triggered a few small (size 1) wind slab avalanches in immediate lee features.
10-25 cm of recent snow is being transported by wind and developing slabs in lee features. The mid-November rain crust is down 30-50 cm, and has been reported up 2100 m.
A couple of crusts are found in the lower snowpack: A thin rain crust from early November is found 40 cm above the ground in deeper snowpacks and at the ground in shallower areas; it likely does not exist above 2300 m. A melt-freeze crust and facets from October is at the base of the snowpack, and possibly only exists above 1900 m.
Snowpack depths range from 50-140 cm at treeline elevations, and exceed 200 cm in the high alpine. Deeper snowpacks are found around the Bugaboos and northern parts of the forecast region. Snowpack depths decrease rapidly below 1700 m.
Early season hazards are very real right now at all elevations, be wary of thin/shallow snowpacks, rocks, stumps, creeks, and other sharks hidden under a dusting of fresh snow.
