Avalanche Forecast
Issued: Dec 17th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs.
dsaly,
Avalanche Canada
Recent snow is gaining cohesion and slab properties over a weak layer of surface hoar. Scattered reports document increasing reactivity, expect to find an increasingly touchy slab more snow and wind on the way.
Summary
Confidence
Weather Forecast
THURSDAY NIGHT - Mainly cloudy with flurries, 5 cm / southwest wind, 25-45 km/h / alpine high temperature near -8
FRIDAY - Cloudy with flurries, 5-15 cm / southwest wind, 45-70 km/h / alpine high temperature near -5
SATURDAY - Snow, 5-15 cm / southwest wind, 45-70 km/h / alpine high temperature near 0 / Freezing level rising to 1500 m
SUNDAY - Flurries, 5-15 cm / southwest wind, 20-40 km/h / alpine high temperature near -5
Avalanche Summary
Snowmobilers remotely triggered a storm slab over surface hoar Wednesday near Allen Creek (MIN report). Keep this in mind as I expect slabs to become increasingly reactive as fresh snow gains cohesion and bonds over a weak and touchy surface hoar layer.
Several large natural avalanches were reported last Friday at Chappel Creek (see this MIN report). These avalanches occurred on south aspects at treeline elevations. Based on the depth of these avalanches, they likely failed on recently buried surface hoar and/or sun crust layers.
Snowpack Summary
About 20-40 cm (with the higher numbers surrounding Blue River) low density snow has buried a layer of surface hoar in many areas. Slabs are becomingly increasingly reactive as fresh snow bonds and gains cohesion where it overlies touchy surface hoar.
A weak layer of surface hoar that was buried about a week ago is now down 30-60 cm. In many areas the weak layer exists as a crust, and in some areas, it has been found as surface hoar.
Near the base of the snowpack is a crust that was buried in early November. This crust likely has weak facets associated with it. There have been no recent avalanches reported on this layer, though it may be possible to trigger from shallow, rocky terrain.
Terrain and Travel
- Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
- Avoid freshly wind loaded terrain features.
- As the storm slab problem gets trickier, the easy solution is to choose more conservative terrain.
Problems
Persistent Slabs
Intermittent snow and flurries continue to stack up, 20-40 cm of recent and fresh snow sits on a weak layer of surface hoar. Expect this layer to be most reactive in wind loaded terrain.
Some areas near Blue River likely have up to 40-60 cm of new snow on this layer, and it will be most reactive in places like this.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 18th, 2020 4:00PM
