Wind Slabs
N
NE
E
SE
S
SW
W
NW
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely
- Size
- 1–4
Winds at ridgetop have been high enough to blow snow into wind slabs behind ridges and other terrain breaks in the alpine and at treeline.
Avalanche forecast
View on mapNorthwest Coastal
Mar 17 – 18, 2012Avalanche Canada
Archived · expired 15 years ago
Avalanche danger
Mon
Tue
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
Highlights
Variability exists within the region. Avalanches resulting from solar warming are possible with the intense March sunshine.
Avalanche problems
Cornices
NNEESESSWWNW- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible - Likely
- Size
- 1–6
Cornices are reported to be very large and potentially unstable at this time, especially given the sunshine and warm daytime temperatures. A cornice fall could be destructive by itself, and may also act as a trigger on the slope below.
Confidence
Fair - Timing or intensity of solar radiation is uncertain
Weather Forecast
Flurries are expected Sunday, Monday is more likely to be dry. Sunny breaks for both days, freezing level around 500 m. Winds light to moderate southerly. Similar weather expected for Tuesday morning, although winds may ramp up from the south building for a frontal system expected to bring snow Tuesday afternoon.
Avalanche Summary
An avalanche cycle occurred on Friday in response to the new snow and wind. Mostly the activity was relatively small and contained within the top 30 cm of the storm snow. However, some larger events up to size 3 were noted. On Thursday, two natural slab avalanches were observed, one size 1.5 on a north aspect at 1250 m with a fracture line 40cm deep in the recent storm snow. The other was a glide release at 575m near Terrace caused by warm temperatures. Numerous wet loose avalanches were also observed. On Wednesday, a size 3 natural cornice failure was observed.
Snowpack Summary
Sporadic strong and variable winds have redistributed moderate amounts of recent storm snow into wind slabs that most commonly exist in the lee of terrain features at treeline and in the alpine. The mid-pack varies greatly depending on location. You may find up to three persistent weak layers. First, a surface hoar layer buried mid-March, now buried 60-80 cm deep, seems to be most prevalent in the mountains around Stewart. Second, a surface hoar layer buried early March, buried around 1 m, has been causing problems north of Terrace. Third, a weak layer comprising surface hoar or facets, buried early February, is now more than 1 m down. This has been causing issues particularly in the north around Ningensaw. However, recent reports indicate this layer is becoming difficult to trigger. Bear in mind that triggering any of these persistent weak layers would likely result in a very large avalanche. Cornices in the region are reported to be very large and potentially unstable.