Wind Slabs
N
NE
E
SE
S
SW
W
NW
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely
- Size
- 1–3
New snow and wind will form new wind slabs in upper elevation lee terrain. The new snow may also be hiding older, larger wind slabs which formed on Thursday.
Avalanche forecast
View on mapPurcells
Mar 12 – 13, 2016Avalanche Canada
Archived · expired 11 years ago
Avalanche danger
Mon
Tue
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
Highlights
Buried weak layers have the potential for very large avalanches. Conservative terrain selection is still required.
Avalanche problems
Cornices
NNEESESSWWNW- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 2–4
Large cornices loom over open bowls and alpine faces. Not only are massive cornice falls a hazard in themselves, but they can also act as a heavy trigger for slab avalanches on the slope below.
Persistent Slabs
NNEESESSWWNW- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 3–5
Persistent weaknesses lie buried in the top 90cm of the snowpack. Although these layers are slowly becoming less likely to trigger, they have the potential to surprise with nasty consequences. I'd continue riding with a conservative mind set.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
Saturday night: 5-15cm of new snow / Strong southwest ridgetop winds / Freezing level at about 1500mSunday: Light flurries with possible sunny breaks / Light to moderate ridgetop winds / Freezing level at about 1400mMonday: 8-12cm of snow / Moderate easterly ridgetop winds / Freezing level at about 1300mTuesday: Mix of sun and cloud / Light ridgetop winds / Freezing level at about 1200m
Avalanche Summary
On Thursday numerous naturally triggered wind slabs (mostly in the size 2 range) were observed at treeline and in the alpine. They occurred in response to new snow and wind. On Friday explosives control continued to produce storm slabs to size 2.5 on a variety of aspects throughout the region. Of note, a size 2.5 persistent slab avalanche was triggered with explosives in the Dogtooth Range. The mid-February layer was the likely culprit in the avalanche. More wind slab activity is expected in response to wind and snow forecast for Saturday night.
Snowpack Summary
Snowfall accumulations on Thursday were in the 10-20cm range. Strong southerly winds redistributed these accumulations into touchy wind slabs at treeline and in the alpine. 30-70 cm recent storm snow overlies a prominent weak layer buried on or around Feb-27. The deepest snow amounts appear to be in the west central area near Kootenay Lake. The Feb-27 weak layer comprises surface hoar and a crust. Recent snowpack test results are mixed, with some tests indicating this layer is gaining strength, while others indicating it can still fail with sudden "pop" results. A deeper weak layer from mid-February is now down 50-80cm. The early January surface hoar/facet layer is typically down 70-120cm. Triggering an avalanche on either of these layers has become unlikely but either still has the isolated potential to produce very large avalanches with a heavy trigger.