Avalanche Forecast
Issued: Dec 16th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
dsaly,
Avalanche Canada
A pulse of flurries is forecasted to drop up to 20 cm. Expect to find a developing slab problem as wind impacts new flurries and older loose, dry snow. Choose conservative terrain and watch for signs of instability such as whumphing, cracking, and recent avalanches.
Summary
Confidence
Moderate - Uncertainty is due to the limited number of field observations. Uncertainty is due to the track & intensity of the incoming weather system.
Weather Forecast
WEDNESDAY NIGHT - Mainly cloudy with isolated flurries, 10-25 cm / southwest wind, 20-40 km/h / alpine high temperature near -7Â
THURSDAY - Flurries, 10-15 cm / southwest wind, 20-40 km/h / alpine high temperature near -7
FRIDAY - Periods of snow, 10-20 cm / southwest wind, 30-60 km/h / alpine high temperature near -6
SATURDAY - Snow, 10-20 cm / southwest wind, 25-55 km/h / alpine high temperature near -3
Avalanche Summary
On Tuesday, several small (size 1-1.5) loose dry avalanches were reactive to skier traffic. Skiers triggered a small (size 1.5) storm slab avalanche in Glacier National Park. And in the South Columbia's, storm slab avalanches were triggered by explosives and skier traffic on East, North, and West aspects above 2000 m; average depth 5-25 cm.Â
With forecasted new snow and moderate to strong southwest winds, slabs will become more reactive to human triggers, especially in wind loaded areas.
Snowpack Summary
20-40 cm of snow has fallen in the region since Wednesday morning. This new snow has buried a weak layer of surface hoar in many areas. This new snow combined with southwest winds will form reactive slabs, especially at higher elevations.Â
A weak layer that was buried about a week ago is now down 40-60 cm. This layer is variable and has been reported to exist as either a crust or surface hoar. In any case, it is a persistent weak layer with a significant load above it now, and it may react easily to human triggers.
Another crust that was buried in early November can be found near the base of the snowpack. There have been no recent avalanches reported on this layer, however it may be possible to trigger it from shallow, rocky terrain.
Terrain and Travel
- Choose conservative terrain and watch for clues of instability.
- Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
- Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
Problems
Storm Slabs
20-40 cm of new snow sits on a weak layer of surface hoar. This new snow combined with southwest winds will develop slabs that will become increasingly reactive through the day.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
40-60 cm of snow sits above a layer of surface hoar and/or crusts.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 17th, 2020 4:00PM
