Avalanche Forecast
Issued: Feb 10th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs.
cgarritty,
Avalanche Canada
Bring your guard up as you approach the wind exposed alpine. A range of older, stubborn and newer, more reactive wind slabs can be found on all aspects. Large hard wind slabs on steep features should be especially concerning.
Summary
Confidence
High -
Weather Forecast
Wednesday night: Clearing. Light north winds.
Thursday: Sunny. Light north winds, shifting northeast and increasing in the afternoon. Alpine high temperatures around -17.
Friday: Sunny with cloud invading and light flurries beginning overnight. Light northeast winds. Alpine high temperatures around -15.
Saturday: Cloudy with continuing scattered flurries bringing about 5 total cm of new snow, easing overnight. Light east winds. Alpine high temperatures around -12.
Avalanche Summary
With cold temperatures gradually robbing the upper snowpack of cohesion, observations from the past few days show a trend away from wind slab releases and toward small loose dry avalanches triggering in steep start zones with skier traffic. That said, a few more small wind slabs were still able to be triggered with ski cutting in the Whistler area on Tuesday.
Notably, a size 3 (very large) persistent slab was remotely triggered (from a distance) by a group of skiers in the McGillivray Pass area (northern South Coast Inland region) on Monday. This occurred on a southwest aspect at 2400 metres. It was described as a hard wind slab formed over the facet layer from late January detailed in our snowpack discussion.
Snowpack Summary
Up to 15 cm of low density snow can be found on the surface in shaded, sheltered areas. In more wind exposed areas this is replaced with a mix of wind-affected surfaces, including wind slabs that are gradually losing cohesion and reactivity under prolonged cold temperatures. A thin recent sun crust may be found right near the surface on solar aspects.
Below this mixed bag of surface conditions, 50-100 cm of settled storm snow sits on a persistent weak layer that consists of facets at upper elevations, surface hoar in sheltered areas, a melt-freeze crust below 1900 m, and a sun crust on south-facing slopes. There could be more than 100 cm on this layer in wind loaded areas. Although this structure is a bit suspect, we have no recent reports of avalanches failing at this interface.
A crust from early December, currently considered dormant, may be found around 200+ cm deep in the snowpack.
Terrain and Travel
- Carefully evaluate steep lines for wind slabs.
- Be aware of highly variable recent wind loading patterns.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
Problems
Wind Slabs
Wind slabs may exist in atypical terrain features due to recent northerly wind direction. Although they tend to facet and lose cohesion in cold temperatures, wind slabs may remain sensitive to human triggers in steep convexities and near ridgetops.
Faceting and loss of cohesion in cornices can make them brittle and prone to fail. Give them a wide berth from above and below.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 11th, 2021 4:00PM
