Wind Slabs
N
NE
E
SE
S
SW
W
NW
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible - Likely
- Size
- 1–2
Recent winds from the southwest have formed wind slabs in open terrain, particularly behind exposed ridges.
Avalanche forecast
View on mapNorth Rockies
Dec 23 – 25, 2019Avalanche Canada
Archived · expired 7 years ago
Avalanche danger
Wed
Thu
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
Highlights
A weak layer buried 30-60 cm deep remains a concern for human triggering. This layer is most likely to be found in the central and northern parts of the region.
Avalanche problems
Persistent Slabs
NNEESESSWWNW- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1.5–3
Weak layers of surface hoar exist in the upper snowpack, especially around Pine Pass and the McGregors. These layers are most likely to be triggered on steep convex slopes at or below treeline that have not previously been well ridden.
Avalanche Summary
Most recent reports of avalanche activity date back to late last week at the tail end of a stormy period. Nonetheless human triggered avalanches remain a concern at all elevations with a buried weak layer 30-60 cm below the surface most specifically in the central and northern parts of the region. See this MIN post from Hasler on Sunday, which uses some great photos to highlight the potential reactivity of the weak layer.
Confidence
No Rating - Uncertainty is due to field data and reports showing a wide variation in conditions throughout the region.
Weather Forecast
MONDAY NIGHT: Clear periods, moderate southwest wind, alpine high temperature around -9 C.
TUESDAY: Mainly cloudy with isolated flurries, light to moderate west wind, alpine high temperature around -8 C.
WEDNESDAY: Mix of sun and cloud, light west wind, alpine high temperature around -10 C.
THURSDAY: Mix of sun and cloud, moderate to strong southwest wind, alpine high temperature around -5 C.
Snowpack Summary
20-40 cm of snow falling late last week as been redistributed by steady wind from the southwest creating wind slabs in open terrain, while soft powder will be preserved in sheltered areas.
The storm snow sits above three weak layers buried between 30 and 60 cm below the surface. These surface hoar and facet/crust layers showed signs of being reactive and have the potential to produce large avalanches. Reports suggest these layers are widespread around Pine Pass and the McGregors, but harder to find around McBride.
The lower snowpack contains several crust layers. In higher snow areas, these are likely well bonded. However, in shallow areas along the eastern slopes, these could be of concern.
Total snowpack depths are approximately 240 cm in the south of the region, 170 cm around Pine Pass and more like 120 cm in areas to the east.
Terrain and Travel
- Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.