Wind Slabs
N
NE
E
SE
S
SW
W
NW
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely - Very Likely
- Size
- 1–4
New snow and wind continue to set up wind slabs behind ridges and terrain breaks. Large cornices also threaten slopes below.
Avalanche forecast
View on mapSouth Rockies
Mar 21 – 22, 2012Avalanche Canada
Archived · expired 15 years ago
Avalanche danger
Fri
Sat
Alpine
4 · High
Treeline
3 · Considerable
Below
2 · Moderate
Highlights
New snow amounts are expected to vary across the region. Bump up the treeline rating to HIGH if there's more than 25 cm new snow; bump the alpine rating down to Considerable if there's less than 15 cm.
Avalanche problems
Storm Slabs
NNEESESSWWNW- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely
- Size
- 1–5
New snow will continue to build storm slabs. It's possible for surface avalanches to step down to a weak persistent layer, initiating large destructive avalanches.
Deep Persistent Slabs
NNEESESSWWNW- Alpine
- Treeline
- Below treeline
- Likelihood
- Unlikely - Possible
- Size
- 4–8
Persistent weak layers, now buried 1-2m deep, still have the potential to produce large and dangerous avalanches. They could be triggered by cornice fall, smaller avalanches stepping down, and under the weight of a snowmobile and rider.
Confidence
Fair - Intensity of incoming weather is uncertain on Thursday
Weather Forecast
20-30 cm new snow overlies a crust that exists on south aspects to around 1900 m and on other aspects to around 1700 m. Recent winds have blown the new snow into wind slabs in exposed lee terrain. Below the crust, two persistent weak layers from mid-February are still being tracked by professionals. The upper one, buried around 16th Feb, is buried approximately 150 cm. The lower one, buried around 9th Feb, is buried typically 180 cm in high snow areas, but as little as 90 cm in low snow areas. Snowpack tests indicate, while both surface hoar layers are becoming more difficult to trigger, they still have the potential to release avalanches, with regular sudden, 'pop' results still being observed.
Avalanche Summary
On Tuesday, wind slabs in the size 1-1.5 range were triggered naturally and by skiers at treeline and above on slopes loaded by south-westerly winds. On Sunday, a size 1.5 avalanche released naturally on a north aspect. On Saturday, a recent avalanche was observed on a north aspect in the southern Elk Valley, suspected to have started as a wind slab and ending in moist snow. Evidence of a previous natural cycle was also reported. On Friday, explosives produced size 1-2 avalanches.
Snowpack Summary
20-30 cm new snow overlies a crust that exists on south aspects to around 1900 m and on other aspects to around 1700 m. Recent winds have blown the new snow into wind slabs in exposed lee terrain. Below the crust, two persistent weak layers from mid-February are still being tracked by professionals. The upper one, buried around 16th Feb, is buried approximately 150 cm. The lower one, buried around 9th Feb, is buried typically 180 cm in high snow areas, but as little as 90 cm in low snow areas. Snowpack tests indicate, while both surface hoar layers are becoming more difficult to trigger, they still have the potential to release avalanches, with regular sudden, 'pop' results still being observed. If avalanches do release on this layer, they will go big. The most likely triggering mechanisms are a person traveling over a thin snowpack area, or a storm slab, wind slab or cornice stepping down. Basal facets may still exist, particularly in shallow snowpack areas with steep, rocky start zones. Cornices have grown large and threaten slopes below.