Avalanche Forecast
Issued: Feb 12th, 2020 5:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
MBender,
Avalanche Canada
Flurries are forecast to bring 5-15 cm of new snow on Thursday. Expect avalanche danger to increase through the day as the snow accumulates and the wind redistributes the snow into reactive slabs.
Summary
Confidence
Moderate - Forecast snowfall amounts are uncertain.
Weather Forecast
Wednesday Night: Mainly cloudy. Moderate southwest wind. Alpine high temperatures around -7.
Thursday: Flurries, accumulation 5-10 cm. Moderate to strong southwest and west wind. Alpine high temperatures around -6. Freezing level 1000 m.
Friday: Isolated flurries. Moderate west wind. Alpine high temperatures around -8. Freezing level 700 m.
Saturday: Cloudy with sunny breaks and isolated flurries. Moderate west wind. Alpine high temperatures around -6. Freezing level 900 m.
Avalanche Summary
On Tuesday there were reports of a few size 1 skier/rider triggered wind slab avalanches at treeline. In the north of the region there were reports of several natural size 2 storm slab avalanches 20-30 cm deep on all aspects in the afternoon.
On Monday there were two reports of cornices failing naturally and triggering wind or storm slabs on slopes below to size 2.5 in the alpine on east and southeast aspects.
There was a report of a remotely triggered (from a distance) size 2.5 deep persistent slab avalanche on Saturday. It was 130 cm deep and triggered in a shallow area at 2300 m on an east aspect.
Snowpack Summary
20-60 cm of snow accumulating through the last week overlies previously wind-affected snow at higher elevations, with diminished depths of about 20-30 cm above a widespread melt-freeze or rain crust up to about 1700 metres. This new snow has been redistributed by winds blowing from a variety of directions.
The mid and lower snowpack are generally well settled, however an aging weak layer of surface hoar from late December, currently buried 70 to 150 cm deep, has shown surprisingly long-lived instability on slopes between 1700-2400 m (above the crust elevation and below the most wind-affected elevations), warranting increased caution around steeper slopes in this elevation band, particularly in the southern half of the region. A facet/crust layer from November may be found near the ground in shallower snowpack areas and has been suspected of being the cause of sporadic very large avalanches releasing in the past 10 days.
Terrain and Travel
- Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
- Wind slabs are most reactive during their formation.
- Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
Problems
Wind Slabs
Recent snowfall combined with shifting winds have built wind slabs on a variety of aspects.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
There are two deeply buried weak layers that are suspected of being the cause of sporadic very large avalanches releasing in the past 10 days. A layer of buried surface hoar may persist in the south of the region at and below treeline. A layer of facets near the base of the snowpack can be found throughout the region in the alpine. Although it is unlikely to trigger these layers, doing so would result in a very large and destructive avalanche.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Feb 13th, 2020 5:00PM
