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Archived

Avalanche Forecast

Dec 17th, 2020–Dec 18th, 2020
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Cariboos.

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.

Confidence

Low - Uncertainty is due to the limited number of field observations. Recent weather patterns have resulted in a high degree of snowpack variability within the region.

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.

Avalanche 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: Likely

Expected Size: 1.5 - 2.5