Avalanche Forecast
Regions: South Coast.
Keep your guard up if you're accessing the alpine, where observations remain limited. Our recent persistent slab problem may not be beyond triggering where firm layers aren't bridging over it.
Confidence
Moderate -
Weather Forecast
Thursday night: Clear. Light to moderate northeast winds
Friday: Sunny. Light to moderate northeast winds. Alpine high temperatures around -10.
Saturday: Cloudy with scattered flurries bringing up to 5 cm of new snow, easing overnight. Light northeast winds. Alpine high temperatures around -8.
Sunday: Cloudy with isolated flurries and a trace of new snow, increasing a bit overnight. Light east or northeast winds, increasing overnight. Alpine high temperatures around -5.
Avalanche Summary
There have been no reports of avalanche activity in the region since early last week when a widespread natural avalanche cycle up to size 3 (very large) took place in the North Shore mountains. Dense bridging layers of snow and crust are expected to have effectively neutralized the problem since that time, although some uncertainty exists with regard to higher alpine locations.
Snowpack Summary
A thin skiff of new snow now exists above a mix of breakable surface crust, wind-affected snow, and old wind slabs that have been losing cohesion under the influence of prolonged cold temperatures. A few cm below this surface, a more supportive crust solidly caps the snowpack below about 1400 metres. This crust may be absent at higher elevations.
100-150 cm of snow sits over a widespread persistent weak layer. This weak layer consists of a thick crust with weak facets on top of it in many areas. In most areas where it remains preserved, this layer has become difficult to trigger due to bridging by overlying dense snow and crusts. There is some concern for the possibility of continued reactivity in steep terrain at high elevations where it has not previously avalanched and where the overlying snowpack may have failed to form an effective bridge over it.
Click here to watch North Shore Rescue's snowpack conditions update from last Friday. This is a reasonable approximation of current conditions as the past week has been a time of slow snowpack change.
Terrain and Travel
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
- Carefully evaluate steep lines for wind slabs.
Avalanche Problems
Persistent Slabs
Isolated steep features in the alpine that did not avalanche during the previous natural cycle may still have potential to produce destructive persistent slab avalanches with a human trigger. Increase caution around steep alpine slopes where a supportive crust layer does not exist near the surface.
Aspects: All aspects.
Elevations: Alpine.
Likelihood: Unlikely - Possible
Expected Size: 1 - 2